Roscommon Equipment Center Program
Project No. 41A
AN ANALYSIS OF GROUND
APPLICATION OF RETARDANTS
Preliminary Report Published December 1985
Reviewed and Printed April 1987
Reformatted for Web Page August 2000
Northeast Forest Fire Supervisors
In Cooperation with
Michigan’s Forest Fire Experiment Station
CONTENTS
Page
Introduction and Objectives ............................................................................................2
Retardant Characteristics and Specifics .........................................................................2
Mixing and Delivery Systems..........................................................................................3
Expansion and Specific Gravity of Retardants................................................................9
Application Rates and Mix Ratios .................................................................................13
Hay Burning Tests ........................................................................................................13
Photographic History of Hay Burning Tests ..................................................................18
Tests Conducted with Phos-Chek® GW................................................................19
Tests Conducted with Fire-Trol® 936L ..................................................................26
Tests - Water Only .................................................................................................35
Field Tests ....................................................................................................................43
Logistics .......................................................................................................................44
Cost ..............................................................................................................................45
Summary ......................................................................................................................46
Caution .........................................................................................................................48
NOTE TO AUGUST 2000 VERSION
This report was reformatted for publication on the internet. The original work was done from 1982-1985.
Some minor editorial revision has been made to enhance the readability of the document. The cost data
has not been updated. Costs are estimates from 1982. The two retardant products used Phos-Chek
GW® and Fire-Trol 936L®, are still available in formulations that are essentially the same. Different
companies now own these brands.
ACKNOWLEDGEMENTS
Grateful appreciation is extended to many who made testing of long-term fire retardants at the Michigan
Forest Fire Experiment Station, Roscommon, Michigan, possible:
Messrs. Don Peterson, H. L. Vandersall, Jerry Berry, and Lou Gildemeister, representatives of the
Monsanto Company. Monsanto, manufacturers of Phos-Chek® dry powder fire retardant, provided a
generous supply for use in our tests.
Messrs. Frank Halsey, Joe Gregel, and Larry P. Moore, representatives of Chemonics Industries.
Chemonics, manufacturers of Fire-Trol® liquid fire retardant, provided a generous supply for use in our
tests.
A special thanks to the personnel of the Michigan Forest Fire Experiment Station for their assistance.
Many talents were combined to carry out this project, including typing and numerous other helpful
additions to the report, equipment development and equipment operation, photography and art work.
1
INTRODUCTION AND OBJECTIVES
The principal objective of this report was to obtain and record as much information as practical related to
the ground application of long-term retardants. Much information in the following report will not be new
for many in fire control who have been using fire retardants. At the risk of "talking down" to those who
have experience with long-term retardants, this report will attempt to inform the least knowledgeable and
will provide some new information for others.
Two retardant products: Fire-Trol® - a liquid concentrate, and Phos-Chek® - a dry powder, were used in
these tests. These long-term retardants have been used for many years on wildfires. Almost all
applications have been via airdrops. In recent years there has been an increasing interest in ground
application of these retardants.
The objectives were:
1. To update information related to these two retardants, and to provide this information to any
interested or potential users.
2. Attempt to verify claims made by the manufacturers of these projects.
3. Determine the cost effectiveness of these chemicals and, in general, record the pros and cons for
using them against traditional methods of controlling wildfire, excluding airdrops.
4. Review several methods and types of equipment used for ground application of these materials.
5. Recommend a policy in general terms related to the proper use of these retardants for ground
application.
It was recognized at the onset that there were unlimited variables and that it would be impractical to deal
with them all. However, it was felt that certain aspects could be controlled to provide insight concerning
ground retardant use. The information contained in this report will not be sufficient to form an absolute
conclusion regarding ground application of retardants. Much additional field experience must supplement
these tests.
RETARDANT CHARACTERISTICS AND SPECIFICS
The following paragraphs are intended to acquaint fire personnel who may have little knowledge of fire
retardants with retardant terminology.
Retardant is often referred to by two types; long-term and short-term. Short-term retardant is usually
used to modify water to make it more effective in suppressing fires. Water can be treated with penetrants
that break the surface tension, allowing the water to be absorbed more easily into the fuels. Thickening
agents are used to help prevent water from running off fuels and to concentrate water on fuel surfaces.
Water can be thickened to consistencies that vary from light syrup to thick pudding. Expansion of water
can be accomplished by using various foaming agents and with the induction of injection of air.
All of these water-modifying methods depend upon the ability of the water to break the heat side of the
fire triangle. Some may have the additional effect of isolating the fuel from the heat.
The characteristic common to all short-term retardant is that they have no affect on fire after the water has
evaporated, or has been driven off by heat. The length of time that short-term retardant is effective is
related to the length of time that water is effective: Hence "Short-term." Regardless of the time limitation
of this type of retardant, they are easy to use and are used extensively.
In comparison, long-term retardant leaves a chemical that is effective after the water (that is used as a
medium in application) has disappeared. The two long-term retardants that are the object of this test
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project are Phos-Chek® GW (dry powder) monoammonium phosphate, and Fire-Trol® 936L (liquid)
ammonium polyphosphate. When heated, these two chemicals lose ammonia, resulting in residual
phosphoric acid that will react with the cellulose portion of wildland fuels. At temperatures in the range of
200-400 degrees centigrade, the phosphoric acid reacts with cellulose forming a phosphate ester. The
material decomposes upon further heating in such as manner that the by-products will not support a
flame. The result is a conversion of the very flammable cellulose to a difficult, flammable, graphite-like
carbon.
Phos-Chek® GW, produced by the Monsanto Company, an be purchased in 40 pound plastic pails, 50
pound bags, or 2,000 pound bins. Phos-Chek® GW is a retardant powder with corrosion inhibitors and
thickening agents added.
Fire-Trol retardant can be purchased in 55-gallon steel drums. Fire-Trol® 936L, used in these tests, is a
liquid concentrate consisting of ammonium polyphosphate, a wetting agent and corrosion inhibitor. It was
designed primarily for ground application and has a deep purple biodegradable dye that allows treated
areas to be readily identified. Fire-Trol® liquid concentrate is intended to be diluted with water to obtain
the desired mix strength.
Chemonics Industries, manufacturers of Fire-Trol® 936L, and Monsanto, producers of Phos-Chek® GW,
have developed these two retardants specifically for ground application and they are intended to be
applied with water pumping equipment. Both companies also produce retardants that are designed for
airdrops.
Information from others, related to toxicity tests, has shown the retardants to be nontoxic when used in
normal concentrations, except to fish. Compounds containing ammonia are toxic to fish. Accidental
application in streams is possible if repeated airdrops are made in proximity to water areas. However,
there should be very little risk to streams or fish when ground application methods are used.
Ammonium phosphate based retardants are basically fertilizers. Over-application to living vegetation can
cause "fertilizer burn" as can over-application of any fertilizer.
Retardant can irritate skin and eyes, particularly open cut or sore, in the same manner table salt does.
Flushing the affected area with water will relieve the problem. Precaution should also be taken so that
the retardant dust is not breathed, or it may cause irritation to the respiratory system.
In general, these retardants are environmentally safe as long as good housekeeping and safety practices
are followed. These fire retardants should not be compared with the polybrominated biphenyl (PBB) fire
retardants that were accidentally mixed with cattle feed in Michigan, which allegedly have been disastrous
to animal and human life. Ammonium phosphate fire retardant has no chemical relationship to PBB.
MIXING AND DELIVERY SYSTEMS
Two approaches have emerged to mix retardant chemicals to their final application strengths. They are
commonly referred to as mixers and blenders.
Retardants in powder form depend almost exclusively on mixing systems to achieve the desired ratio of
retardant and water to produce ready-to-use material. A mixing system relies on combining water and
retardant powder in known quantities. That is, a known amount of powder is added to a known volume of
water to produce a retardant solution of the desired strength ratio. The mixed solution can then be
discharged from ground tankers or airdrop.
Blenders, as related to ground applicators, are devices usually connected to the intake side of the water
pump that controls the flow of liquids into the pump. When using liquid type fire retardants, blenders can
be used to meter the proper amount of water and retardant to produce the desired blend. The blended
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product is directly discharged at the fire site, and is not carried in a mixed form on the tanker, as is the
case when using mixers. In general, powdered retardants use mixers and liquid retardants use blenders.
The nature of the two fire retardants in these tests, one powder and the other liquid, indicates that both
systems (mixers and blenders) may have a decided impact upon how chemicals are used in ground
application.
Phos-Chek® retardant powder can be mixed in at least two ways: one is by pouring a known amount of
powder into a known quantity of water and agitating it. Agitation is accomplished by stirring with a stick or
by more sophisticated mechanical agitators, including the ground tanker's pumping system. The other
method is to use the tanker's pumping system as an eductor. Monsanto has developed three procedures
that utilize the latter method.
1. Pail mixer - This is a small hand-held device used in conjunction with a tank and pumping system that
mixes the retardant directly from pails.
2. Barrel mixer - Similar to the above in concept, but the retardant is poured from pails or bags into a
small container from which the mixing is done.
3. Retardant ground tanker - This concept employs the same mixing principle. A Mixing chamber is built
into the ground tanker and powder is poured into it. The material from the mix chamber is circulated
and recirculated into the water compartment of the ground tanker until the desired amount of powder
has been added.
Figure #1 shows the mixing principle used with all three procedures. Mixing powder and water to produce
ready-to-use retardant of a specific ratio requires that the quantities of powder and water must be exactly
known.
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Although the powder-water retardant solution does not require continuous agitation, the insoluble
components can settle out over an extended period of time. In this system the solution should be
recirculated or otherwise agitated prior to application. The mixing and application of powder retardants
will be covered more comprehensively later in this report.
As stated earlier, blenders are used almost exclusively with liquid type retardants. Chemonics Industries
has developed a retardant blender system for ground application. It can also be used for preparing
ready-to-use mix for airdrops.
Prior to 1977, Chemonics Industries made a search for and an evaluation of, existing blenders, but was
unable to find a blender they could recommend for uniform application of liquid retardants from a ground
vehicle. The need was self-evident. To control ratios accurately over a range of flows, a blender would
have to operate on demand and meter both water and liquid concentrate separately at the required ratios.
Because of this need, the Howard Blender was invented (patent pending). The Howard Blender controls
the flow from a water supply and also the flow from a liquid retardant supply. The system utilizes tow
canister type components, one for water and one for retardant. Each canister has a vacuum diaphragm
that works in balance with the fire pump intake vacuum. An external vacuum controller (an electrically
operated vacuum pump) is required to maintain this balance. The main purpose of this aspect of the
Howard Blender is to negate the influence of the different heights of water and retardant levels in their
respective reservoirs. In addition, a calibrated metering valve, one for each liquid, is used to produce the
ratio of the mix. The calibrations allow for mix ratios from two parts water: one part retardant to 10 parts
water: one part retardant.
The above explanation of the Howard Blender is not sufficient to do it justice. Interested readers should
contact Chemonics Industries, Phoenix, Arizona, for more detailed information.
Figure 2 shows a simple blender that may prove to be useful for a demand-type retardant application
system. As the diagram shows, a water supply and retardant supply are connected to the pump's intake.
The San Dimas Technology & Development Center (SDTDC), U.S. Forest Service, has run evaluation
tests on the Howard Blender. Since that time, field applications of the system have shown some
difficulties related to its use. Potential users of this blender are encouraged to obtain SDTDC’s reports for
further information.
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Orifices of specific sizes are placed in the water and retardant lines. The ratio of the area of the two
orifices is relative to the amounts of water and retardant to be blended. The orifices can be fixed or
adjusted in size.
A water bypass loop with a control valve provides for using water only. By closing the retardant control
valve and opening the water control valve, water can be utilized in the normal manner.
Check valves in the water and retardant lines allow the fluid to flow in one direction only to prevent the
accidental mixing of water and retardant.
This blender is intended to be used primarily for liquid retardant. However, it should be possible to use
powder that has been mixed into a solution. The blend of retardant and water will be affected by the
varying level elevation of the water compared to the retardant. Any accumulation or lodging of insoluble
particles in the orifice will also alter the blend's mix ratio.
After reviewing all of the aspects of testing the two long-term fire retardants, one liquid and one powder, it
was decided to develop our own version of a mixing system. We needed a system that would handle
liquid or powder and would assure an accurate mix ratio. Some considerations that led to the
development of this system were:
1. It must be a demand system, i.e.; it must be able to discharge retardant or water and have both
available at the fire site. This means that a nozzleman would have the capability of intermittent use of
either water or retardant.
2. It must be able to mix at different ratios accurately enough to be used in laboratory type tests.
3. The system should provide the maximum on-board and on-demand potential possible, related to
volume.
4. It should be as foolproof as possible to prevent the accidental migration or mixing of either water or
retardant.
5. Materials and mechanisms should resist corrosion and minimize spills related to mixing.
At the time retardant testing was undertaken by the Michigan Forest Fire Experiment Station, a 1500
gallon 6-wheel-drive tanker was being constructed. It was decided to build retardant capability into this
unit in order to make a prototype retardant tanker and provide a vehicle for testing retardant. The design
of this tanker, excluding the retardant feature, is documented in blueprint form in Roscommon Equipment
Center Project No. 39. REC Project No. 42 will illustrate the details for modifying the 1500-gallon tank for
retardant use.
Figure 3 and the following description will help the reader to understand how the mixing system works.
The all-steel tank consisted of three compartments totally isolated from each other; the only way material
could be put into them was through the top of the compartments. A 125-gallon compartment concentrate
chamber and the adjacent mix chamber of 160 gallons are fiberglass lined. The remainder of the tank is
reserved for water.
The concentrate chamber can hold 125 gallons of liquid Fire-Trol®. Phos-Chek® powder must be
premixed into a liquid solution. The potential amount of ready-to-use retardant, related to using powder,
depends upon how much powder is concentrated in water (pounds per gallon) and carried in the 125
gallon concentrate chamber. This principle will be covered more completely later.
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An eductor, Number 3 (see Figure 3), was used to transfer quantities of concentrated retardant into the
160-gallon mix chamber. A flexible plastic tube, Number 6, was connected to the suction opening of the
eductor and to the intake-opening elbow, Number 7. The intake-opening elbow was attached to a
vertically positioned threaded rod, Number 8. When the threaded rod is rotated it moves the intake
opening up or down, depending on the direction of rotation. Components Number 6, 7, and 8, were
located on the inside of the concentrate chamber.
On the outside of the concentrate chamber, another threaded rod, Number 10, was connected to the
inside rod at the top with a chain drive. The chain drive, Number 5, was above the concentrate tank and
does not come in contact with the retardant. The chain drive had a 1:1 ratio that synchronized the
rotation of the two threaded rods. An indicator, Number 14, was attached to the outside rod and was
indexed to indicate the position of the eductor intake-opening elbow.
Number 12 was a clear plastic visual sight tube that allowed the operator to determine the exact level of
concentrate on board. The indicator runs up or down on a calibrated rod. The rod was calibrated in 5gallon increments.
The size of the mix chamber was 160 gallons. To mix a batch of 4:1, the operator would check the visual
sight tube and position the indicator in line with the fluid level shown in the sight tube. A 4:1 mix ratio has
5 units: 1 unit of concentrate (32 gallons) and 4 units of water (128 gallons). To aid the operator, a chart
was used to mix water and concentrate in any ratio. When the amount of concentrate required was
determined, the operator lowered the indicator (in this case the equivalent of 32 gallons), using the
calibrated rod to determine the correct amount.
Because the eductor intake opening was synchronized with the indicator, it was submerged in the
concentrate, 32 gallons deep. Water pressure was then directed through the eductor from the pump
discharge. This water emptied into the mix chamber. As it passed through the eductor it picked up the
32 gallons of retardant concentrate. The two liquids mixed together and eventually filled the 160-gallon
mixing chamber. An overflow tube indicated when the mixing chamber was full. At that moment, the
operator shut off the water pressure completing a mix of 160 gallons at 4:1 ratio - 32 gallons of retardant
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and 128 gallons of water. It took approximately three minutes to mix a 160-gallon batch of ready-to-use
retardant. The time is related to the size of the water pump and to the capacity of the eductor.
The intake system of the pump was connected to the water chamber and the ready-to-mix chamber. A
selector valve, Number 20, allowed the operator to switch from one material to the other at will.
The ready-to-use retardant mix could be agitated by circulating it through the pumping system. It will be
necessary to agitate the mix before application if it has set for an extended period.
The mixing system described in the preceding paragraphs and illustrated by Figure 3, proved to be
workable and was used in these tests. A limited amount of satisfactory experience has shown that this
system may have some merit as a practical concept. It is referred to as a "Known Quantity Batch Mixer."
The term relates to mixing the materials in known quantities and in batches. The batch size is limited to
the size of the mix chamber.
A batch system of this nature has some decided limitations such as: the user is limited to the volume of
the mix chamber. When this amount of ready-to-use retardant has been used, the operator must stop
application and mix a new batch.
A portion of the water reservoir must be reserved for the mix chamber. The size of the chamber logically
should be in proportion to the overall capacity of the tanker. This may put an unrealistic demand on small
units. This limitation can be largely offset by the fact that the mix chamber can be used to carry water
and that it does not have to be used for retardant until it is desired to mix a batch. It is possible to use the
entire water vessel as a mixing chamber. In this case, all elements and areas of the tank should be
protected from corrosion. The ammonia phosphate retardants will remove the zinc coating of galvanized
water tanks. Fiberglass and stainless steel are alternatives. The corrosion inhibitors of these chemicals
will help protect bare carbon steel unless diluted.
If the entire tank is used as a mixing chamber, it will be necessary to determine the exact quantity of
water involved in order to produce the desired mix ratio.
The "Known Quantity Batch Mixer" will be referred to again at various points in the remainder of this
report.
It seems obvious that all ground tankers equipped to apply long-term retardant on demand, allowing the
use of water or retardant intermittently, will necessarily have a storage compartment for unmixed
retardant. The amount of space allotted for the material will determine the useful volume of the ground
tanker.
Liquid concentrate (Fire-Trol®) can be easily carried on a tanker if a compartment has been provided for
this purpose. Fire-Trol® is a concentrated form of fire retardant and is intended to be diluted with water
for application on fire. An example illustrating the potential of a ground tanker using Fire-Trol® would be
a unit having a 125 gallon concentrate chamber capacity that can be mixed with water at a 4:1 ratio. This
would result in a potential volume of 625 ready-to-use gallons. Higher ratios of water-to-retardant would
increase the potential, lower ratios would decrease the potential.
The U.S. Forest Service has established mix ratios for airdrops of 4:1 for Fire-Trol® liquid concentrate,
and 1 pound to 1 gallon for Phos-Chek® powder retardant. Assuming these ratios are valid for ground
application, the implication is that the two retardants are equal in performance when mixed at these
ratios. Using this point for comparison, Phos-Chek® powder mixed with water would have to be
concentrated many times greater than 1 pound to 1 gallon to provide the same potential as Fire-Trol®
liquid, if they were to be carried on board a ground tanker in the same size compartment. Example - a
125 gallon concentrate chamber filled with Fire-Trol® that can be mixed with water at a 4:1 ratio has a
potential of 625 ready-to-use gallons. If the same 125 gallon concentrate chamber was filled with PhosChek® mixed 1 pound to 1 gallon, the potential is only 125 gallons.
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This led to the conclusion that mixing powder retardant in water, in sufficient amounts, could produce a
concentrate solution that would equal liquid concentrate. If this could be accomplished, more options
would be available related to the application of powder type retardants by ground tankers. This is
especially true when a demand type system is required.
Phos-Chek® powder can be carried in dry form in volumes that would equal the potential of liquid
concentrate. However, the space that it must be allotted on a ground tanker is considerably more than
that required for liquid.
Tests were conducted to investigate the possibility of concentrating powder in a slurry and later diluting it
for application at different mix ratios. The next section of this report deals with expansion and specific
gravity of retardants mixed with water at varying strengths.
EXPANSION AND SPECIFIC GRAVITY OF RETARDANTS
Expansion and specific gravity are two important physical properties that can affect retardant use. The
amount of expansion of a powder retardant in water may be critical if the user desires a concentrated
solution. Likewise, specific gravity will affect vehicle load and the pumping system involved with retardant
delivery. Because of this, tests were done to determine the expansion and specific gravity of PhosChek® GW and the specific gravity of Fire-Trol® 936L.
To determine these properties for Phos-Chek®, water at 60 degrees F. was carefully measured in a
graduated cylinder to obtain 500 milliliters. This amount of water was also weighed with a gram scale as
a crosscheck for accuracy. Phos-Chek® powder was weighed on a gram scale in amounts that would
produce mix ratios from 0.9 pounds to 1 gallon and up, to 7 pounds to 1 gallon. Each of these mixtures
was measured in the graduated cylinder to determine the volume and the percent expansion. A
hydrometer was used to find the specific gravity. Figures 4, 5, and 6, show the results.
Figure 4 - Phos-Chek
Expansion and Specific Gravity for Various Mix Ratios
Ratio of Mix
Expansion
in ML
Percent
Expansion
Water ML 60 deg.
Phos-Chek
in Grams
Specific
Gravity
520
4.0
500
53.92
1.056
522
4.4
500
59.91
1.062
527
5.3
500
68.30
1.069
535
7.0
500
83.87
1.082
539
7.8
500
95.86
1.090
550
10.0
500
119.82
1.109
580
16.0
500
179.73
1.142
618
23.6
500
239.64
1.172
645
29.0
500
299.55
1.205
675
35.0
500
359.46
1.230
710
42.0
500
419.37
1.245
The above information was obtained by actual measurements.
Total
Weight
549.6
554.3
562.8
578.6
590.5
614.6
674.1
736.3
792.3
849.8
909.8
Pounds
0.9
1.0
1.14
1.4
1.6
2.0
3.0
4.0
5.0
6.0
7.0
Gallons
1
1
1
1
1
1
1
1
1
1
1
From Figure 5, the expansion rate of Phos-Chek® is approximately a straight-line relationship. The
overall expansion of 7 pounds to 1 gallon was 42 percent. A careful examination of the expansion rates
recorded will reveal some discrepancies. There is a possibility that small samples of Phos-Chek®, mixed
as described in the expansion test, do not necessarily reflect the true expansion of material used in larger
volumes. A small sample of Phos-Chek® powder may not have the same consistency of the overall
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average of larger amounts. It appears safe to assume that a 4 percent to 6 percent expansion will occur
for each pound of Phos-Chek® that is added per gallon of water.
The expansion of Phos-Chek® solutions must be considered if these solutions are to be diluted back to a
weaker ready-to-use mixture. Figure 7 shows the amount of concentrated Phos-Chek solution to use for
various concentrations and for four ready-to-use mix ratios. This information is related to the "Known
Quantity Batch System" described earlier. The size of the concentrate chamber, the mix chamber, and
the expansion factors were used to develop this chart.
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Figure 7 - Phos-Chek® Slurry Mixing Chart
323.2
404.4
484.4
555.5
612.2
0.9 lbs/gal
75.8
53.3
42.6
35.5
31.0
27.9
1.0 lbs/gal
84.3
59.2
47.3
39.5
34.4
31.08
1.14
lbs/gal
96.0
67.4
53.9
45.0
39.2
35.4
1.6 lbs/gal
134.8
94.7
75.6
63.0
55.0
49.7
Potential
Supply in
Gallons of
1:1 Mix
Gallons of
concentrate per 160
gal. of Ready-to-Use
Slurry.
227.2
Ready to Use
Slurry Strength
To produce 160 gallons of ready-to-use slurry at mix strengths of 0.9, 1, 1.14, and 1.6 made from 2 to 7
pounds per gallon concentrated slurry, use the following amounts.
Concentration - Pounds to Gallons
2
3
4
5
6
7
Example Calculation:
125 gal. Concentration chamber capacity
________________________________________________________
= 88.02 gal. of water needed
1.42 exp factor for 7 lb:1 gal (see Figure 4)
88.02 gal. x 7 lb. powder = 616.2 lbs. of Phos-Chek® for 125 gals. @7 lbs.:1 gal.
To produce 160 gal. of ready-to-use slurry @ 1 lb.:1 gal.:
160 gal mix chamber
_______________________________________________
= 153.25 gal.
1.044 expansion factor for 1 lb:1 gal
125 gal concentrate chamber
153.25 gal x
_______________________________________
= 31.08 gal.
616.2 lbs. Phos-Chek®
The specific gravity of Fire-Trol® 936L liquid concentrate was determined for various mix ratios from 2:1
to 8:1. These are recorded in Figures 8 and 9. The hydrometer readings were taken with the solution at
60 degrees F.
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Figure 8 - Fire-Trol®
(Liquid Concentrate - L.C.)
Weights and Specific Gravity
Specific Gravity
60 deg.
Mix Ratio
L.C. Wt.
Grams
Water
Volume
1st Sample 2nd Sample
200 ML
2:1
1.130
11.32
282.3
400 ML
3:1
1.114
1.118
282.3
600 ML
4:1
1.094
1.096
282.3
800 ML
5:1
1.080
1.080
282.3
1000 ML
6:1
1.066
1.066
282.3
1200 ML
7:1
1.060
1.058
282.3
1400 ML
8:1
1.050
1.050
282.3
1600 ML
The above information was obtained by actual measurements.
Total Wt.
of Mix
Volume
CU. Disp.
% Decrease
in Vol.
677.1
876.5
1077.0
1276.0
1473.0
1676.0
1878.0
590 ML
780 ML
879 ML
1180 ML
1380 ML
1580 ML
1780 ML
1.7
2.5
2.0
1.7
1.4
1.3
1.1
Figure 9 - Application Chart
This chart shows the relationship between Rate (gallons per 100 sq. ft.), GPM (gallons per minute) and
FPM (feet per minute), based on a retardant line constructed 3 feet wide. The following equations were
used to develop the chart:
GPM = R x FPM x AG
A.G. Factor = Actual Line Width
33-1/3
3 Feet
FPM = GPM x 33-1/3 x AF
AF =
3 Ft
R
Actual Line Width
R = GPM x 33-1/3
FPM
Rate
GPM
1/2
1
2
3
4
5
6
7
8
9
10
11
12
Feet per Minute (FPM)
Gals.
100 sq ft
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
133
67
33
22
17
13
11
9.5
8.3
267
133
67
44
33
27
22
19
17
15
400
200
100
67
50
40
33
29
25
22
20
533
266
133
89
67
53
44
38
33
29
27
24
333
167
111
83
67
56
48
42
37
33
30
400
200
133
100
80
67
57
50
44
40
36
33
466
232
155
117
93
78
67
58
52
47
42
39
533
266
178
133
107
89
76
67
59
53
48
44
299
200
150
120
100
86
75
67
60
54
50
332
222
167
133
111
95
83
74
67
61
56
365
244
184
147
122
105
92
81
73
67
61
398
266
200
160
133
114
100
89
80
73
67
433
289
217
173
144
124
108
96
87
79
72
467
322
233
187
156
133
117
104
93
85
78
500
356
250
200
167
142
125
111
100
91
83
378
267
213
178
152
133
118
107
97
89
283
267
189
162
142
126
113
103
94
To construct lines other than 3 feet wide, the GPM or FPM should be multiplied by "AG" factor or "AF
factor.
AG = Adjusted gallons per minute.
AF = Adjusted feet per minute.
A hydrometer could be used to determine mix ratios, especially when mixing unknown quantities of water
or retardant. In this case, the operator would have to make repeated checks with a hydrometer as the
retardant is added to the water. When the predetermined specific gravity is reached, the batch would be
ready. It should be noted that the temperature of the solution would affect hydrometer readings.
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APPLICATION RATES AND MIX RATIOS
Application rates and mix ratios are two main factors involved in using retardants. These two aspects
affect the effectiveness of the retardants and the cost of using them. The mix ratio is the volume of water
to the volume of retardant of Fire-Trol® of a mixed solution. For Phos-Chek® powder it is the weight of
Phos-Chek® to the volume of water. The application rate is the volume of mixed solution applied per unit
area of the fuel.
Figure 9 was developed to help control the amounts of retardant applied to fuel in this project's hay
burning tests. Monsanto and Chemonics have recommendations for application rates that range from 1/2
gallon per 100 square feet, to 12 gallons per 100 square feet. This chart covers the entire recommended
range and also the discharge rate from the application nozzle, 2 GPM to 34 GPM. It also relates the rate
per 100 square feet and gallons per minute to feet per minute. Example: if the application rate is 5
gallons at 100 square feet, and the discharge volume is 12 GPM, the forward progress in the application
process would be 80 FPM. This figure is based on a firebreak constructed 3 feet wide. If fire breaks
were to be constructed at widths different than 3 feet wide, the 80 FPM figure can be multiplied by an
approximate factor that is also shown on this chart.
The application chart proved most useful for the hay burning tests. However, it can only be used as a
guideline for application on actual wildfire situations. The application rate may be the most difficult thing
to control and places a great deal of responsibility on the nozzleman.
The first step in controlling the application rate is knowing the exact discharge volume. This implies that
the nozzle orifice and the pressure must be coordinated and controlled to maintain a consistent volume
rate. The other facets of the application rate, area to be treated, and the time in which to make
application, will be entirely up to the nozzleman's judgment. These two factors can drastically affect the
cost of using retardants from ground tankers.
The mix ratio, retardant to water, can be controlled fairly accurately. Ratios ranging from 2:1 up to 10:1
for liquid concentrate (Fire-Trol®) have been recommended. Monsanto recommends a mix of 0.96
lbs./gal for Phos-Chek® powder. The mix ratios for either Phos-Chek® or Fire-Trol® will affect the cost,
but the accuracy of the ratio may not be that critical for ground tanker use if the application rates cannot
be controlled. The application rate becomes ultra-important when rich mix ratios are used. Rich mixes
will be desirable when treating heavy slash type fuels or elevated fuels. Using less water will help prevent
the retardant from running off the fuel and becoming ineffective. Rich mixes also mean less need for
water. The added cost of rich mixes makes it imperative that the application rate be carefully controlled.
There are numerous options available for ground application of retardant as opposed to airdrops;
however, these options will require adequate equipment and training to take advantage of them. More
information related to application rates and mix ratios will be covered in the next section.
HAY BURNING TEST
It was envisioned that the following hay burning tests would give the opportunity to accurately control,
within practical limits, the mix ratios and the application rates. The fuel type and fuel loading could also
be controlled. The plan was to run the burn tests under controlled conditions, including weather
prescriptions, to enable us to relate the results to known and consistent facts.
It was apparent from the beginning that it would be impractical to test all of the combinations of ratio of
mix and rate of application that are implied by the chemical companies. Multiplying 12 different
application rates (in 1 gallon increments) by as many as 14 mix ratios (includes Phos-Chek® and Fire-
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Trol®) makes 168 tests. Add to this another variable, time delay between application of retardant and
ignition, and it becomes obvious that there are unlimited variables that can affect the results.
Figure 10 shows basic information about each hay-burning test. One bale of hay, an average weight of
48 pounds, was used for each plot. Each plot was 6 feet wide and 33-1/3 feet long, or 200 square feet
(see Photo 1). This corresponds to a fine fuel loading of 5-1/4 tons per acre. One half of this area was
treated (100-sq. ft.) and the other half was left untreated. The untreated hay was ignited so that the fire
would spread to the treated 100 sq. ft. A worksheet was used to record all pertinent information such as
weather, application rate, mix ratio, retardant used, time delay, dimension of the plot and additional
comments. Each plot was assigned a number to coincide with the worksheet number. An identification
number card was placed near each plot and photographed with the burn. This procedure crossreferenced all of the burn tests with the hay plot sheet, the work sheet, and the photograph. Some
variations of the dimensions were used as indicated by numbers 38, 29, 40, and 41, on the test plot
sheet.
Water alone was used on some plots to make a comparison of effectiveness. The time delay aspect was
an attempt to determine how much effect the water, mixed with the retardant, had on retardation. A
series of time delays were used with the water only tests. They ranged from 11 minutes to 2 hours. It
should be understood that the water only tests were related to pretreating of the fuels to produce a wet
line, or a defensive barrier, as opposed to using water in a direct application on the fire. Direct application
of water on the fire would produce dramatically different results.
As stated earlier, the application rate is related to the volume discharge rate (GPM) and the speed at
which the line building process proceeds. A system was developed to control the application rate of the
retardant to the hay burning plots.
A Forester "Six-shooter" nozzle was attached to the hose reel of the 1500 gallon tanker. The nozzle was
calibrated, using the fog pattern only. Figure 11 shows the empirically derived values related the orifice
number, pressure gage reading and volume discharge rate for the pumping system used. The desired
volume discharge rate was obtained by choosing an orifice and setting a micro-adjustment on the pump
engine throttle to obtain to obtain the necessary pressure.
Figure 11 - Nozzle Calibration
Fog Pattern Only
Forester "Six Shooter" Nozzle
Model WGC-4 Pacific Pump
Orifice No.
1
2
3
4
5
6
Note:
55/4
80/10
105/16
N.O./1
60/7
90/13
GPM At Specific Pressure Gauge Readings
First Figure is PSI - Second Figure is GPM (PSI/GPM)
70/5
95/6
115/7
140/8
90/11
105/12
115/13
135/14
110/17
115/18
120/19
130/20
68/2
100/3
135/4
162/5
78/8
100/9
120/10
140/11
100/14
110/15
120/16
130/17
160/9
0/15
N.O./21
N.O./6
155/12
140/18
The above measurements were obtained by actually discharging water into a calibrated container. The
pressure readings were recorded when the given GPM was obtained. Considerable trial and error was
involved.
Some inconsistencies in the increment of increase in pressure readings from one GPM to the next appear in
this chart. These inconsistencies are most likely due to the method used to measure the elements of this
chart, i.e., pressure, gallons, and time.
Pressure readings were taken at the pump. The nozzle was located at the end of 150 feet of 1-inch ID hose.
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The Forester nozzle was mounted on a small garden tractor. The discharge hose from the tanker
supplied the desired retardant to be tested. Figure 12 shows the basic concept. The object of this
arrangement was to control the amount of retardant applied to the hay plot in a one-pass operation.
Adjustments of the boom were intended to position the nozzle to produce a 3-foot wide spray pattern on
the fuel. The forward speed of the tractor was calibrated and Figure 13 was compiled.
With this arrangement, the application rate could be established with some degree of accuracy. By using
the application chart (Figure 9), the feet-per-minute chart (Figure 13 - Speed of Tractor), and the nozzle
calibration chart (Figure 11), it was possible to treat the 100 square foot hay plots in one pass with a
predetermined amount of retardant.
Although a great effort was made to control all aspects of the hay burning tests, some difficulties did
arise. The fog pattern deposited upon the fuel was not always 3 feet wide. The width was reasonably
consistent and it was deemed impractical to attempt improving upon the application system.
Results of the hay burning tests were displayed in two ways. A summary chart is provided for the tests of
each fire retardant. Also, photographs of the burning of most plots are provided with captions. The
reader is requested to refer to both the narrative and photographic information when analyzing the
results.
At the beginning of the hay burning tests, the intention was to simultaneously treat two identical hay plots,
one with water and one with retardant. The two plots were to be burned at approximately the same time.
The time delay between treating and ignition would be nearly the same. Using this concept, the
respective test plots were identified with a number and a letter. The letters “W” for water and “R” for
retardant indicate the treatment of each plot. Example: test plots #1W and #1R were treated
simultaneously and also burned after the same time delay to obtain a direct comparison of the retardant's
performance. The letter designation was dropped after test plot #12 in favor of using a different number
for each test plot.
Figure 13. Riding Garden Tractor Forward Speeds
All speeds are at full governed engine throttle w/180 lb. operator riding.
Transmission
Gear
Transmission
Notch No.
Seconds
@ 100 Feet
FPM
MPH
260.0
187.5
128.0
107.0
23.07
32.0
46.8
56.07
0.262
1st
1
3
5
7
1
3
5
7
90.0
65.0
45.0
37.0
66.66
92.3
133.3
162.0
1.84
1
3
5
7
50.0
35.5
25.0
20.5
120.0
179.0
240.0
292.6
3.3
1
3
5
7
34.0
24.0
17.0
176.47
250.0
352.9
4.0
2nd
3rd
4th
0.636
Please note that in the hay-burning summary that follows, a judgment was made as to whether the
treated line held. This was a subjective judgment made by the researcher with single criteria: "Would the
fire have crossed the treated area and continued to burn had fuel been present?" In some cases a
definitive judgment was not possible.
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16
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17
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PHOTOGRAPHIC HISTORY OF HAY BURNING TESTS
The following pages present a photo history of the retardant tests. Because of the multitude of variables
in the burning situations, the reader is urged to analyze each burn to help get a feel for retardant
effectiveness. The first series depicts tests of Phos-Chek® followed by Fire-Trol® and the water only
experiments.
Cost figures are listed for each retardant burn. These figures are based on 1982 prices provided to us by
the manufacturer. Costs may vary due to shipping and purchase quantity. These costs are listed only to
give the reader a general idea of how much retardant application would cost; it is not intended to be a
cost comparison between the two products tested in this report. Because of limited data and variable
burning conditions, making direct comparison between the two retardants is not practical, based on these
tests.
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Tests Conducted with Phos-Chek® GW
Photo #15
Test plot #1R burning.
Photo #16)
Test plot #1R treated with Phos-Chek® GW
Application rate:
1 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 1 lb/100 sq ft
Time delay:
1 hour
Retardant cost:
$0.77/100 sq ft
Temperature:
82 deg
Wind speed:
2-3 mph
Humidity:
37%
Effect: Total loss of line. There was a distinctly darker charred
appearance to the fuel that was treated. The ash left
by the untreated fuel indicated that it had been less
consumed than the untreated fuel.
Photo #20
Test plot #2R being ignited.
Photo #21
Test plot #2R burning.
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Photo #22
Test plot #2R treated with Phos-Chek® GW
Application rate:
2 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 1.9 lb/100 sq ft
Time delay:
1 hour
Retardant cost:
$1.52/100 sq ft
Temperature:
82 deg
Wind speed:
2-3 mph
Humidity:
37%
Effect: Total loss of line. Underlying fuel of treated area was
not totally consumed.
Photo #31
Test plot #3R. Dense smoke created as fire
burned into retardant treated area.
Photo #34
Test plot #3R treated with Phos-Chek®
Application rate:
3 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 2.9 gal/100 sq ft
Time delay:
1 hour, 25 minutes
Retardant cost:
$2.30/100 sq ft
Temperature:
75 deg
Wind speed:
2-3 mph
Humidity:
37%
Effect: Treated fuel showed an increased resistance to burning
compared to test plot #2R. Line was lost, however.
Photo #35
Test plot #4R treated with Phos-Chek®
Application rate:
3 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 2.9 gal/100 sq ft
Time delay:
1 hour, 19 minutes
Retardant cost:
$2.30/100 sq ft
Temperature:
84 deg
Wind speed:
Light & variable
Humidity:
54%
Effect: The same application as #3R, the results were also
similar. Line was lost.
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Photo #36
Test plot #5R treated with Phos-Chek®
Application rate:
4 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 3.8 gal/100 sq ft
Time delay:
1 hour, 27 minutes
Retardant cost:
$3.07
Temperature:
84 deg
Wind speed:
Light & variable, up to 5 mph
Humidity:
51%
Effect: Long finger-shaped burn areas were created. Fire was
retarded, but escaped across treated area.
Photo #37
Test plot #6R treated with Phos-Chek® GW
Application rate:
5 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 4.8 gal/100 sq ft
Time delay:
1 hour, 30 minutes
Retardant cost:
$3.83
Temperature:
84 deg
Wind speed:
Light & variable, up to 5 mph
Humidity:
51%
Effect: Initial run of flame ignited far side of fuel, probably edge
was treated with less concentration. Inadequate
application to protect line.
Photo #38
Test plot #7R treated with Phos-Chek® GW
Application rate:
6 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 5.7 gal/100 sq ft
Time delay:
1 hour, 31 minutes
Retardant cost:
$4.59
Temperature:
84 deg
Wind speed:
Light & variable, up to 5 mph
Humidity:
51%
Effect: See caption for test plot #9R.
Photo #39
Test plot #8R treated with Phos-Chek® GW
Application rate:
Mix ratio:
Amount of retardant:
Time delay:
Retardant cost:
Temperature:
Wind speed:
Humidity:
21
7 gal/100 sq ft
1 lb/gal
7.7 gal/100 sq ft
1 hour, 41 minutes
$5.36
84 deg
Light & variable, up to 5 mph
51%
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Photo #42
Test plot #9R treated with Phos-Chek® GW
Application rate:
8 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 7.7 gal/100 sq ft
Time delay:
1 hour, 35 minutes
Retardant cost:
$6.13
Temperature:
84 deg
Wind speed:
Light & variable, up to 5 mph
Humidity:
51%
Effect: Tests #4R, #5R, #6R, #7R, #8R, and #9R, were all run
on the same day (08/16/82). The delay time averaged
approximately 1 hour, 30 minutes. The application rate
for Test #4R was 3 gal/100 sq ft. It was increased by
one gallon on each of the succeeding test plots #5R,
#6R, #7R, #8R, and #9R.
Photographs #35, #36, #37, #38, #39, and #42,
provide visual evidence of the effectiveness of the
treatment for each test plot.
A mistake was made when applying retardant to test plot #9R.
The treated area that burned was accidentally treated with
water only. Photograph #44 is of the same test plot, but was
taken from a different angle. This test, because of the mistake,
provided an excellent comparison of the effectiveness of the
water only treatment (8 gal/100 sq ft) and the Phos-Chek®
treatment (8 gal/100 sq ft).
Photographs #49, #50, #52, #53, #54, and #56, are of test plots
applied with Phos-Chek® GW that were burned on the same
day (08/17/82). The time delay for these tests were extended
to approximately 2-1/4 hours.
Photo #50
Test plot #10R treated with Phos-Chek® GW
Application rate:
6 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 5.7 gal/100 sq ft
Time delay:
2 hours, 13 minutes
Retardant cost:
$4.59
Temperature:
76 deg
Wind speed:
Variable, up to 6 mph
Humidity:
41%
Effect: Treated area did not burn. Small spots ignited, but
went out. This test is a repeat of test #7R, Photo #38,
except for different weather and longer time delay.
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Photo #53
Test plot #11R treated with Phos-Chek® GW
Application rate:
7 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 6.7 gal/100 sq ft
Time delay:
2 hours, 14 minutes
Retardant cost:
$5.36
Temperature:
76 deg
Wind speed:
Variable, up to 6 mph
Humidity:
41%
Effect: See caption for Photo #57, test plot #12R.
Photo #57
Test plot #10R treated with Phos-Chek® GW
Application rate:
8 gal/100 sq ft
Mix ratio:
1 lb/gal
Amount of retardant: 7.7 gal/100 sq ft
Time delay:
2 hours, 15 minutes
Retardant cost:
$6.13
Temperature:
76 deg
Wind speed:
Variable, up to 6 mph
Humidity:
41%
Effect: Test plot #10R was treated with the same application
rate and mix ratio as was test pot #7R (Photo #38).
The air temperature was 84 deg for test plot #6R and
76 deg for test plot #10R. The time delay was
approximately 45 minutes longer for test plot #10R.
These two photographs (#38 and #51) provide
evidence that for a 1 lb/gal mix, 6 gal/100 sq ft is the
breaking point where fire did not spread across the
treated area. Test plot #6R (Photo #37) seems to
reinforce this evidence.
Test plots #11R and #12R (Photos #53 and #56)
treated with 7 and 8 gal/100 sq ft were extremely
effective. Fire was extinguished rapidly at the treated
line with no smoldering embers remaining.
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Photos #109 and #110
Test plot #43 treated with Phos-Chek® GW
Application rate:
1 gal/100 sq ft
Mix ratio:
8 lb/gal
Amount of retardant: 0.8 lbs/100 sq ft
Time delay:
1 hour, 2 minutes
Retardant cost:
$0.62
Temperature:
67 deg
Wind speed:
Light & variable
Humidity:
44%
Effect: A narrow strip of the treated area shows good
resistance to burning. This area probably had a higher
concentration of retardant than the 1 gal/100 sq ft that
was intended.
Tests #43 to #48 were all completed on the same day.
The air temperature was 66-67 deg, considerably
cooler than some of the previous test days.
Photo #111
Test plot #44 treated with Phos-Chek® GW
Application rate:
2 gal/100 sq ft
Mix ratio:
8 lb/gal
Amount of retardant: 1.5 lb/100 sq ft
Time delay:
1 hour, 11 minutes
Retardant cost:
$1.24
Temperature:
67 deg
Wind speed:
Light & variable
Humidity:
44%
Effect: Fire spread across top; underlying fuel was not
consumed.
Photo #113
Test plot #45 treated with Phos-Chek® GW
Application rate:
3 gal/100 sq ft
Mix ratio:
8 lb/gal
Amount of retardant: 2.3 lb/100 sq ft
Time delay:
1 hour, 12 minutes
Retardant cost:
$1.92
Temperature:
67 deg
Wind speed:
Light & variable
Humidity:
44%
Effect: Treated area was about 30 inches wide instead of 36
inches. The far edge away from the untreated area
was missed when applying retardant. The area that
did receive the 3 gallons did not burn. The
concentration of retardant on the 30 inch area was
probably 20% greater than the intended 3 gal/100 sq ft,
or about 3.6 gal/100 sq ft.
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Photo #115
Test plot #46 treated with Phos-Chek® GW
Application rate:
4 gal/100 sq ft
Mix ratio:
8 lb/gal
Amount of retardant: 3.1 lb/100 sq ft
Time delay:
2 hours, 3 minutes
Retardant cost:
$2.47
Temperature:
66 deg
Wind speed:
Light & variable
Humidity:
44%
Effect: Fire escaped across treated area in an uneven pattern.
About 50% of the line was effective. Gusts of wind
during this burn had some influence on the
effectiveness of the treated area.
Photo Not Available
Test plot #47 treated with Phos-Chek® GW
Application rate:
5 gal/100 sq ft
Mix ratio:
8 lb/gal
Amount of retardant: 3.9 lb/100 sq ft
Time delay:
2 hours, 4 minutes
Retardant cost:
$3.20
Temperature:
66 deg
Wind speed:
Light & variable
Humidity:
44%
Effect: Fire escaped across approximately 50% of the treated area.
Photo #116
Test plot #48 treated with Phos-Chek® GW
Application rate:
Mix ratio:
Amount of retardant:
Time delay:
Retardant cost:
Temperature:
Wind speed:
Humidity:
Effect: Very effective.
25
6 gal/100 sq ft
8 lb/gal
4.6 lb/100 sq ft
2 hours, 10 minutes
$3.71
66 deg
Light & variable
44%
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Tests Conducted with Fire-Trol 936L*
Photo #59
Fire-Trol® retardant being applied.
Photo #60
Test plot treated with Fire-Trol®.
This picture depicts the effectiveness of the dye in Fire-Trol®.
For cost effective use, the user will need to know how much
retardant is adequate in a situation. Then the user will need to
know when he has applied that amount. It is likely that the dye
will provide the clue to discriminating the amount of application.
Photo #62
Test plot #13 treated with Fire-Trol® 936L
Application rate:
3 gal/100 sq ft
Mix ratio:
4:1 (4 gal water to 1 gal Fire-Trol®)
Amount of retardant: 0.6 gal/100 sq ft
Time delay:
2 hours, 22 minutes
Retardant cost:
$2.40
Temperature:
78 deg
Wind speed:
Light & variable
Humidity:
39%
Effect: Fire escaped across approximately 30% of the treated
area.
Photo #63
Test plot #14 treated with Fire-Trol® 936L
Application rate:
4 gal/100 sq ft
Mix ratio:
4:1
Amount of retardant: 0.8 gal/100 sq ft
Time delay:
2 hours, 22 minutes
Retardant cost:
$3.20
Temperature:
78 deg
Wind speed:
Light & variable
Humidity:
39%
Effect: Similar to test plot #13, but slightly more effective.
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Photo #65
Test plot #16 treated with Fire-Trol® 936L
Application rate:
6 gal/100 sq ft
Mix ratio:
4:1
Amount of retardant: 1.2 gal/100 sq ft
Time delay:
2 hours, 24 minutes
Retardant cost:
$4.80
Temperature:
78 deg
Wind speed:
Light & variable
Humidity:
39%
Effect: Variable wind had a greater influence on this test than
on tests #13 and #14. Fire escaped across untreated
area leaving much of the underlying treated fuel
unburned.
Photo #66
Test plot #17 treated with Fire-Trol® 936L
Application rate:
7 gal/100 sq ft
Mix ratio:
4:1
Amount of retardant: 1.4 gal/100 sq ft
Time delay:
2 hours, 25 minutes
Retardant cost:
$5.60
Temperature:
78 deg
Wind speed:
Light & variable
Humidity:
39%
Effect: Fire did not burn across entire width of treated areas;
however, fire may have escaped in an actual field
situation. This test was greatly influenced by a variable
wind that gusted up to 7 mph.
Photo #67
Test plot #18 treated with Fire-Trol® 936L
Application rate:
8 gal/100 sq ft
Mix ratio:
4:1
Amount of retardant: 1.6 gal/100 sq ft
Time delay:
2 hours, 2 minutes
Retardant cost:
$6.40
Temperature:
78 deg
Wind speed:
Light & variable
Humidity:
39%
Effect: Treated area did not burn. Center section, that did
burn, was omitted during application process.
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Test plots 19 through 24 were treated with Fire-Trol® 936L and were all burned the same day.
Photos #68 and #69
Test plot #19 treated with Fire-Trol® 936L
Application rate:
3 gal/100 sq ft
Mix ratio:
4:1
Amount of retardant: 0.6 gal/100 sq ft
Time delay:
1 hour, 30 minutes
Retardant cost:
$2.40
Temperature:
80 deg
Wind speed:
Light & variable
Humidity:
71%
Effect: Fire escaped across surface of treated fuel. Underlying
fuel that was treated was not totally consumed, which
was a contrast to the untreated area.
Photo #68 shows the intensity of the fire.
Photo #70
Test plot #20 treated with Fire-Trol® 936L
Application rate:
4 gal/100 sq ft
Mix ratio:
4:1
Amount of retardant: 0.8 gal/100 sq ft
Time delay:
1 hour, 31 minutes
Retardant cost:
$3.20
Temperature:
80 deg
Wind speed:
Light & variable
Humidity:
71%
Effect: Treated area was lightly scorched and burned on the
surface only. Underlying fuel did not burn. The 3 ft
wide treated area probably would not have been wide
enough to prevent the fire from spreading to untreated
fuel in an actual wildfire condition.
Photo #71
Test plot #21 treated with Fire-Trol® 936L
Application rate:
5 gal/100 sq ft
Mix ratio:
4:1
Amount of retardant: 1.0 gal/100 sq ft
Time delay:
1 hour, 32 minutes
Retardant cost:
$4.00
Temperature:
80 deg
Wind speed:
Light & variable
Humidity:
71%
Effect: About the same as test plot #20. Fire was actually
stopped by the retardant, but some surface fuel
ignited, carrying fire across the treated area. In a
wildfire situation the fire would have escaped.
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Photo #72 and #73
Test plot #22 treated with Fire-Trol® 936L
Application rate:
6 gal/100 sq ft
Mix ratio:
4:1
Amount of retardant: 1.2 gal/100 sq ft
Time delay:
1 hour, 31 minutes
Retardant cost:
$4.80
Temperature:
80 deg
Wind speed:
Light & variable
Humidity:
71%
Effect: The intensity of the fire was greater than in test #21.
Wind had a greater influence.
Photo #72 shows fuel burning.
Photo #74
Test plot #23 treated with Fire-Trol® 936L
Application rate:
7 gal/100 sq ft
Mix ratio:
4:1
Amount of retardant: 1.4 gal/100 sq ft
Time delay:
1 hour, 34 minutes
Retardant cost:
$5.60
Temperature:
80 deg
Wind speed:
Light & variable, up to 6 mph
Humidity:
71%
Effect: Retardant held. Fire was more intense than Test #21.
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Photo #75 and #76
Test plot #24 treated with Fire-Trol® 936L
Application rate:
8 gal/100 sq ft
Mix ratio:
4:1
Amount of retardant: 1.6 gal/100 sq ft
Time delay:
1 hour, 31 minutes
Retardant cost:
$6.40
Temperature:
80 deg
Wind speed:
Light & variable, up to 6 mph
Humidity:
71%
Effect: The test plot was not treated properly. The far edge
away from the fire was missed when applying
retardant. The treated line was also less than the
intended 3 ft. This test should not be used for
comparative purposes.
Photo #88
Test plot #31 treated with Fire-Trol® 936L
Application rate:
1 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 0.3 gal/100 sq ft
Time delay:
2 hours, 5 minutes
Retardant cost:
$1.33
Temperature:
74 deg
Wind speed:
Gusty, up to 9 mph
Humidity:
50%
Effect: Complete burn. Treated area was evident by dark
color. The amount of retardant actually applied was
questionable. Tests should be repeated. (See
following page.)
Photo #89
Test plot #32 treated with Fire-Trol® 936L
Application rate:
2 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 0.7 gal/100 sq ft
Time delay:
1 hour, 7 minutes
Retardant cost:
$2.66
Temperature:
74 deg
Wind speed:
Gusty, 0-9 mph
Humidity:
50%
Effect: Fire burned across surface. Isolated areas did not
burn. Fire tended to creep under surface fuels that
were treated. Much of the underlying fuels did not
burn.
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Photo #90
Test plot #33 treated with Fire-Trol® 936L
Application rate:
3 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 1.0 gal/100 sq ft
Time delay:
1 hour, 9 minutes
Retardant cost:
$4.00
Temperature:
74 deg
Wind speed:
Gusty, 0-9 mph
Humidity:
50%
Effect: Treated area only slightly scorched; seemed very
effective. Wind conditions not quite as severe as in
Test #32.
Photo #91, #92, and #93
Test plot #34 treated with Fire-Trol® 936L
Application rate:
4 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 1.3 gal/100 sq ft
Time delay:
2 hours
Retardant cost:
$5.33
Temperature:
70 deg
Wind speed:
Gusty, 0-9 mph
Humidity:
50%
Effect: Surface of treated area held very effectively. Treatment
seemed to be deeper into underlying fuels than in
Tests #32 and #33.
Dense white smoke that was created when fire burned
into treated area, as shown by Photo #92, was typical
of many of the test burns.
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Photo #99
Test plot #35 treated with Fire-Trol® 936L
Application rate:
5 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 1.7 gal/100 sq ft
Time delay:
24 hours, 18 minutes
Retardant cost:
$6.66
Temperature:
77 deg
Wind speed:
Light, up to 5 mph
Humidity:
55%
Effect: The important factor of this test is that it was ignited 24
hours after treatment. The retardant effectiveness was
impressive. An attempt to reignite the treated area
with a fuel oil torch was unsuccessful. Hay burned
only where it was coated with fuel oil.
The air temperature at ignition time was 66 deg,
somewhat lower than some of the previous tests.
Photo #104
Test plot #36 treated with Fire-Trol® 936L
Application rate:
6 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 2.0 gal/100 sq ft
Time delay:
48 hours
Retardant cost:
$8.00
Temperature:
66 deg
Wind speed:
Light & variable, up to 7 mph
Humidity:
37%
Effect: Wind direction varied during burn. Hay plot did not
burn with as much intensity as some of the other tests.
A light rain occurred at about 7:00 a.m. (10/01/82), but
drying conditions were excellent. Fuel moisture was
low. Retardant material did not wash off and was still
very effective.
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Photo #97 and #98
Test plot #37 treated with Fire-Trol® 936L
Application rate:
1 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 0.3 gal/100 sq ft
Time delay:
1 hour, 6 minutes
Retardant cost:
$1.33
Temperature:
77 deg
Wind speed:
Light & variable, up to 5 mph
Humidity:
55%
Effect: Complete loss of line. Top surface almost all black.
Much of the underlying treated fuel was not consumed.
This test was intended to be a repeat of Test #31.
Photo #94
Shows a test plot 10 ft wide x 14-1/2 ft long, treated with FireTrol®. These dimensions are typical of test plots #38, #39,
#40, and #41. The treated area of these plots are unlike all
other test plots involved in the hay burning sequence.
Four test plots were established to provide a wider fire barrier
than the 3 ft used on all other burns. The hay plots were
divided into three widths. The first 3 ft were left untreated. The
next 12 in. were treated with a heavier concentration of
retardant, volume wise, than the remaining 6 ft. The objective
was to produce a concentrate retardant barrier at the edge of
the fire front. The remaining area was treated with a light coat
of retardant and was intended to prevent ignition of the fuel
from spotting or from exposure of the advancing flame and
heat.
The total area treated equals 100 sq ft. The application rate
was controlled by discharging retardant solution at a known
volume (GPM) and by timing with a stop watch.
Photo #102
Test plot #38 treated with Fire-Trol® 936L
Application rate:
2 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 0.7 gal/100 sq ft
Time delay:
2 hours, 10 minutes
Retardant cost:
$2.66
Temperature:
79 deg
Wind speed:
Light & variable, up to 5 mph
Humidity:
50%
Effect: Untreated area burned intensely. Treated area burned
slowly. Fire burned unusually long (9 minutes). Fire
would have escaped in a wildfire situation.
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Photo #103
Test plot #39 treated with Fire-Trol® 936L
Application rate:
3 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 1.0 gal/100 sq ft
Time delay:
2 hours, 19 minutes
Retardant cost:
$4.00
Temperature:
79 deg
Wind speed:
Light & variable, up to 5 mph
Humidity:
50%
Effect: Fire burned with good direction, but possibly was not as
intense as in test #38. Very effective. Test plot #38 is
shown in the background.
Photo #105
Test plot #40 treated with Fire-Trol® 936L
Application rate:
4 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 1.3 gal/100 sq ft
Time delay:
24 hours, 30 minutes
Retardant cost:
$5.33
Temperature:
66 deg
Wind speed:
Light & variable, up to 7 mph
Humidity:
37%
Effect: Wind direction was not favorable. Burned less severely
than tests #38 and #39.
Photo #106
Test plot #41 treated with Fire-Trol® 936L
Application rate:
Mix ratio:
Amount of retardant:
Time delay:
Retardant cost:
Temperature:
Wind speed:
Humidity:
Effect: Very effective.
5 gal/100 sq ft
2:1
1.7 gal/100 sq ft
24 hours, 45 minutes
$6.66
66 deg
Light & variable, up to 7 mph
37%
Photo #108
Test plot #42 treated with Fire-Trol® 936L
Application rate:
5 gal/100 sq ft
Mix ratio:
2:1
Amount of retardant: 1.7 gal/100 sq ft
Time delay:
25 hours, 17 minutes
Retardant cost:
$6.66
Temperature:
66 deg
Wind speed:
Light & variable, up to 7 mph
Humidity:
37%
Effect: Ran out of retardant near end of test plot. Completed
treating remainder with water. Photograph shows
extreme contrast between retardant and water.
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Water Only Tests
Photo #10
Test plot #1W treated with Water
Application rate:
1 gal/100 sq ft
Time delay:
1 hour, 15 minutes
Temperature:
82 deg
Wind speed:
2-3 mph
Humidity:
37%
Effect: Water not effective.
Photo #12
Test plot #1W after burn.
Photo #17
Test plot #2W; untreated area burning
Temperature:
Wind speed:
Humidity:
82 deg
2-3 mph
37%
Photo #19
Test plot #2W treated with Water
Application rate:
Time delay:
Temperature:
Wind speed:
Humidity:
Effect: Loss of line.
35
2 gal/100 sq ft
1 hour, 30 minutes
82 deg
2-3 mph
37%
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Photo #26
Test plot #3W; fire spreads to wet line
Photo #27
Test plot #3W treated with Water
Application rate:
Time delay:
Temperature:
Wind speed:
Humidity:
Effect: Loss of line.
3 gal/100 sq ft
1 hour, 53 minutes
75 deg
2-3 mph
37%
Photo #49
Test plot #10W treated with Water Only
Application rate:
6 gal/100 sq ft
Time delay:
2 hours, 16 minutes
Temperature:
76 deg
Wind speed:
Variable, up to 6 mph
Humidity:
41%
Effect: Complete burn with very little evidence of retardation.
Photo #52
Test plot #11W treated with Water Only
Application rate:
Time delay:
Temperature:
Wind speed:
Humidity:
Effect: Loss of line.
36
7 gal/100 sq ft
2 hours, 16 minutes
76 deg
Variable, up to 6 mph
41%
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Photo #55
Test plot #12W treated with Water Only
Application rate:
Time delay:
37
8 gal/100 sq ft
2 hours, 19 minutes
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Test plots 25 through 30 were treated with water only. These tests were intended to determine the
retarding effect water had related to increasing time delays and application rates. The information
obtained should help in deciding when retardants should be used instead of water.
Photo #77
Test plot #25 treated with Water Only
Application rate:
3 gal/100 sq ft
Time delay:
11 minutes
Temperature:
64 deg
Wind speed:
Light, up to 5 mph
Humidity:
50%
Effect: Fire continued to advance slowly into water treated
area. Last skiff of smoke vanished 28 minutes after
ignition. Treated line was effective in stopping spread
of fire; however, it appeared that the long lasting
smoldering could reignite and continue to spread.
Photo #78 and #79
Test plot #26 treated with Water Only
Application rate:
4 gal/100 sq ft
Time delay:
31 minutes
Temperature:
64 deg
Wind speed:
Light, up to 5 mph
Humidity:
50%
Effect: Treated area held, but was less effective than test #25.
Photo #80
Test plot #27 treated with Water Only
Application rate:
5 gal/100 sq ft
Time delay:
1 hour, 3 minutes
Temperature:
65 deg
Wind speed:
Light, up to 5 mph
Humidity:
50%
Effect: Surface of hay much drier than underneath. Fire swept
across surface and ignited in scattered spots.
Underlying fuel had 50-80% moisture content.
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Photo #82
Test plot #28
Application rate:
6 gal/100 sq ft
Time delay:
1 hours, 30 minutes
Temperature:
66 deg
Wind speed:
Light, up to 5 mph
Humidity:
47%
Effect: More surface fuel burned than in test #27. Underlying
fuel still damp and effective. Fire would have escaped
in actual wildfire situation.
Photos #83 and #84
Test plot #29 treated with Water Only
Application rate:
7 gal/100 sq ft
Time delay:
2 hours
Temperature:
67 deg
Wind speed:
Light, 4.5 to 5 mph
Humidity:
47%
Effect: Top surface burned across; complete loss of line.
Underlying fuel still damp.
Photo #86
Test plot #30 treated with Water Only
Application rate:
8 gal/100 sq ft
Time delay:
2 hours, 2 minutes
Temperature:
67 deg
Wind speed:
Light, up to 5 mph
Humidity:
47%
Effect: Top surface burned across. Underlying fuel still damp,
did not burn. Complete loss of line. Fire more intense
than test #29.
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HAY BURNING SUMMARY
FIRETROL® 936L WITH MIX RATIO OF 4 GALLONS WATER TO 1 GALLON FIRETROL®.
Test Plot #
19
13
20
14
21
22
16
23
17
24
18
Retardant Mix
Application Rate
Gal/100 sq ft
3
3
4
4
5
6
6
7
7
8
8
Amount of
Retardant
Gal/100 sq ft
0.6
0.6
0.8
0.8
1.0
1.2
1.2
1.4
1.4
1.6
1.6
Time Delay
Before Ignition
Hr/Min
1:30
2:22
1:31
2:22
1:32
1:31
2:24
1:34
2:25
1:31
2:20
Line Held
No
No
No
No
No
No
--1
Yes
--1
Yes2
Yes
FIRETROL® 936L WITH 2 GALLONS WATER TO 1 GALLON FIRETROL®.
Test Plot #
31
37
32
33
34
35
42
36
Retardant Mix
Application Rate
Gal/100 sq ft
1
1
2
3
4
5
5
6
Amount of
Retardant
Gal/100 sq ft
0.3
0.3
0.7
1.0
1.3
1.7
1.7
2.0
Time Delay
Before Ignition
Hr/Min
1:06
1:06
1:07
1:09
2:00
24:18
25:17
48:00
Line Held
No
No
No
Yes
Yes
Yes
Yes2
Yes3
1
Test was affected by strong variable winds.
Observers judged that line held where retardant had been fire burned across section missed by
retardant application.
3
A light rain fell during the morning of ignition; however, good drying conditions prevailed in the six hours
between rain and ignition. Fuel moisture was low and the light rain apparently did not wash off much
retardant.
2
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PHOS-CHEK® WITH MIX RATIO OF 1 POUND RETARDANT TO 1 GALLON WATER.
Test Plot #
1R
2R
3R
4R
5R
6R
7R
10R
8R
11R
9R
12R
Retardant Mix
Application Rate
Gal/100 sq ft
1
1
3
3
4
5
6
6
7
7
8
8
Amount of
Retardant
Gal/100 sq ft4
1.0
1.9
2.9
2.9
3.8
4.8
5.7
5.7
6.7
6.7
7.7
7.7
Time Delay
Before Ignition
Hr/Min
1:00
1:00
1:25
1:19
1:27
1:30
1:31
2:13
1:41
2:14
1:35
2:15
Line Held
No
No
No
No
No
No
Yes
Yes5
Yes
Yes
Yes
Yes
PHOS-CHEK® WITH 0.8 POUNDS RETARDANT TO 1 GALLON WATER.
Test Plot #
43
44
45
46
47
48
4
5
Retardant Mix
Application Rate
Gal/100 sq ft
1
2
3
4
5
6
Amount of
Retardant
Gal/100 sq ft4
0.8
1.5
2.3
3.1
3.9
4.6
Time Delay
Before Ignition
Hr/Min
1:02
1:11
1:12
2:03
2:04
2:10
Line Held
No
No
No
No
No
Yes
The amount of retardant used is adjusted for expansion.
Small spots occurred in applied area, but line held.
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WATER ONLY TESTS.
Test Plot Number
Application Rate
Gal/100 sq ft
1W
2W
3W
10W
11W
12W
25
26
27
28
29
30
1
2
3
6
7
8
3
4
5
6
7
8
Time Delay Before
Ignition
Hr:Min
1:15
1:30
1:53
2:16
2:16
2:19
0:11
0:31
1:03
1:30
2:00
2:02
Line Held
No
No
No
No
No
No
Yes6
Yes
No7
No7
No7
No7
6
The water line held; however, the fire smoldered in the application area for 28 minutes after ignition.
Fire swept across surface fuels of treated area; underlying fuel had 40-80% moisture content and did
not burn.
7
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FIELD TESTS
At the time of writing, the Forest Fire Experiment Station’s use of Fire-Trol® and Phos-Chek® on wildfire
type conditions has been limited. Some experimentation on prescribed burns was done in a preliminary
fashion.
In the spring of 1984, several prescribed burns were conducted in jackpine slash. Temperatures were in
the low 70’s with relative humidities in the low 20’s. In one trial, retardant was applied adjacent to the
plow furrows on the downwind side of a burn. Photo #150 shows the tanker applying the retardant via its
fender nozzle. The spray pattern varied from 17 to 25 feet wide.
Photo #150:
nozzles.
Application of mixed retardant through fender
Other Important Data:
Mix rate
5:1 Fire-Trol®
Application rate (estimated)
0.4 gal/100 sq ft of retardant
2.9 gal/100 sq ft of mixture
Delay before ignition: 16 minutes
Photo #151 shows the flame laying across the line. Retardant applied area is to the right. Similar
conditions occurred across the 100 yard test area with no spot fires. Spot fires should have been a
problem on this day.
Photo #151: Retardant applied to right side of plow lines (see
text).
Photo #152 shows a jackpine slash pile that had a total one gallon of liquid concentrate retardant applied
(6 gallons of 5:1 mix). Photo #153 shows the intensity of the fire as it traverses the area of the pile. Note
in Photo #154 that many of the fine twigs were left after the fire passed through. A similar pile with 6
gallons of water had all fine fuels and twigs consumed.
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Photo #152: Slash pile applied with liquid concentrate before
burn. Application: 6 gallons of 5:1 mix (1 gallon of liquid
concentrate retardant).
Photo #153: Burn photo near slash pile on Photo #152.
Photo #154: Slash pile after the burn. Fine twigs still intact.
Please note that the amount of retardant applied in these prescribed burns was not controlled. The
prescribed burn experience reinforced the belief that trained judgement on the part of the person
controlling the nozzle will be necessary. Future research plans will center on wildfire and prescribed fire
experience.
LOGISTICS
The supply and transportation of retardant to fire sites for ground tanker use will require some planning
and, in some cases, certain equipment will be needed. Needless to say, before retardant can be used in
the field for fire control, a supply must be established. If retardant is expected to be used upon demand,
a supply must be available to charge or recharge ground tankers that are capable of using it. The use of
retardant is not feasible for ground application if a supply of material is not available at or near the fire
location.
If Phos-Chek® dry powder is used and mixed at 1 pound to 1 gallon, 25 40-pound pails would be required
for every 1000 gallons of solution used. Amounts of this magnitude will require an additional vehicle, in
the 3/4-ton pickup class, to deliver retardant material for refill at the fire site. It is unlikely that even a
large tanker vehicle could carry this amount of dry powder on board. It seems impractical to provide the
space needed on the retardant tanker to carry this much dry powder. Smaller retardant tankers will rely
even more on an auxiliary fire site supply for recharging.
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The 40-pound plastic pails make convenient, easy to handle packages for Phos-Chek® powder; however,
they must be available to the ground tanker. Utilizing the full capacity of a ground tanker to carry
premixed retardant solutions eliminates the possibility of "use upon demand" of retardant or water.
Fire-Trol® is supplied in 55 gallon drums. Fire-Trol® 936L weighs approximately 11-3/4 pounds per
gallon, or 646 pounds per 55 gallons. It is impractical to handle this weight at a fire site. That is, it cannot
be easily moved from one vehicle to another. A small transfer pump would probably be the most logical
means to charge a retardant tanker from the 55-gallon drums. One drum will produce 275 gallons of
ready-to-use solution mixed at a ratio of 4:1.
Providing the potential of 1000 gallons of ready-to-use solution (4:1) would require 3.6 drums of liquid
concentrate. Similar to transporting Phos-Chek® to the fire site, it would require a 3/4 ton pickup to carry
the amount necessary for a 1000 gallon potential. A large retardant tanker can carry a significant amount
of liquid concentrate if a holding chamber is planned and integrated into the design of the unit. The 1500gallon retardant tanker used for these tests, utilizing the batch system described earlier, can carry 125
gallons of liquid concentrate. This amount of concentrated retardant gives the tanker a potential of 625
gallons, mixed 4:1. It would have to be recharged from a supply vehicle after the initial 125 gallons were
expended. About one mile of fire line, 3 feet wide, can be treated at the rate of 4 gallons per 100 square
feet, with 625 gallons of retardant solution.
Pickup size retardant tankers would require utilizing the full tank capacity for holding the retardant mix. At
a treatment rate of 4 gallons per 100 square feet, a 150-gallon supply would make about a quarter mile of
fire line 3 feet wide. Small pickup-size retardant tankers can be effectively utilized, but they would have to
be recharged more frequently.
Many possibilities seem to exist for supplying retardant to ground tankers. Small amounts can be carried
on tankers and dispensed on demand. If large amounts of retardant are required, more elaborate supply
mechanisms will have to be established.
COST
The cost of retardant materials used by ground tankers is directly related to the application rate and the
mix ratio. Ideally, to minimize the cost, the amount of retardant used should be the least amount that is
effective. The correct amount may be difficult to ascertain. Retardant applied in amounts that are
ineffective will be a total waste. Over application can increase the costs dramatically.
At the time of this writing, the hay burning test is the only major evidence available (from this test project)
that can be applied to make a calculated judgment related to the amounts that should be used.
With further research, minimum effective cost per coverage area of retardant can probably be established
for long-term application. The water element of the retardant solution is effective only for short-term
situations. For long-term situations, the amount of retardant chemical applied to the fuel is the element
that determines its effectiveness. Using this perception, retardant solution of different mix ratios can have
the same effectiveness if the amounts applied are adjusted accordingly. As an example, Fire-Trol®
mixed 2:1 and applied at the rate of 4 gallons per 100 square feet would cost the same as a 5:1 mix
applied at the ratio of 8 gallons per 100 square feet. Both solutions should have about the same effect on
fire for long-term application. It seems reasonable to say that long-term retardant should not be used for
short-term use. Water alone may provide the same results. However, if water cannot be applied in
sufficient amounts, the added cost of a retardant may be justified for short-term application.
Phos-Chek® powder mixed 1 pound to 1 gallon, and Fire-Trol® liquid mixed 4:1, will cost about the same
per gallon. This is based on $0.80 per pound for Phos-Chek® and $4.00 per gallon for Fire-Trol®. These
prices were current in 1982. The cost of each test plot of the hay burning tests is related to these figures.
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A cost comparison, using retardants from ground tankers against other traditional methods and
equipment, is difficult to make. Retardant use will be an added cost to tanker operations that normally
use water only. Each agency will need to analyze whether this added initial cost will be justified in terms
of the total economics of the forest fire.
SUMMARY
The positive aspects of long-term retardant make them worthy of consideration for ground application in
wildfire control. The results of burning tests showed that Phos-Chek® GW and Fire-Trol® 936L are
effective retardants. Long-term retardants that can be applied by ground equipment provide an additional
tool that can be used in conjunction with other proven methods and techniques.
These retardants; however, must also compete with traditional type fire tools. They must be cost
effective. If fire retardants are used in situations where water alone would be effective, they would have
to be considered very expensive. On the other hand, if other methods are not effective, the cost of fire
retardants may be entirely reasonable.
Some instances that may justify the cost of using retardants are:
1. If it is environmentally damaging to use earth moving equipment such as fire line plows and
bulldozers.
2. If terrain and soil conditions prevent the use of line building equipment.
3. Fire proofing areas that have high concentrated values such as building structures, power poles, and
valuable tree species.
4. Pretreating hazardous areas such as fuel storage areas or an area that must be evacuated before the
fire arrives. The long-term retarding aspects would be important when a time delay is unavoidable
between application and exposure to fire.
The mixing and application of long-term fire retardants will require special equipment over and above the
normal components used on "water only" tankers. Retrofitting of retardant mixers or blenders may be
possible on existing units, but a retardant tanker that has been designed and built to perform the task will
probably be the best choice.
The dry chemical retardant mixing equipment for ground tankers, developed by Monsanto, described by
USDA Equip Tips (January 1982) can do an efficient job of mixing. The Barrel Mixer and Pail Mixer use
the same principle for mixing powder retardants. This principle was also used to mix Phos-Chek® GW
and water for use in the test project. Figure 1, page 5, helps explain the mixing process.
The slip-on retardant tanker shown by USDA Equip Tips (January 1982) has a 125-gallon capacity.
Larger units utilizing the same mixing principle can be built. The main limitation of this mixing principle is
that it does not allow for intermittent use of retardant or water on demand by the user; it uses the full
capacity of the water tank as a mix tank. Once the tank has been filled with retardant solution, there is no
choice. The retardant must be used, needed or not!
The Known Quantities Batch System, shown by Figure 3, page 9, and explained in the test of this report,
has three chambers:
1. A concentrate chamber to store concentrated retardants in liquid form.
2. A mix chamber to mix and hold ready-to-use solution of the desired strength ratio.
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3. A much larger chamber to store water only.
On a large system of this design a reasonable amount of space can be reserved for the concentrate and
for mixing. It may not be reasonable to allot sufficient space for these two chambers on small tanker
units. The mix chamber can, however, be used to carry water until it is desired to mix retardant. In this
case the water in the mix chamber can be mixed with concentrate. This procedure would utilize the mix
chamber more efficiently. The overall water capacity of the tanker would not be diminished by the size of
the mix chamber.
Liquid concentrate or powder solution can be used by the Known Quantity Batch System. Powder,
however, must be premixed and stored in the concentrate chamber in a solution. Concentrated solutions
of 5 pounds to 1 gallon have been successfully used. The concentrated powder solution can be diluted,
with water, to the desired ready-to-use strength the same as liquid type fire retardants. Quantity charts
for various mix ratios will be required to assist the operator in the dilution process for this system. Figures
7A and 7B are examples.
From this data, it appears that the minimum cost of retardant for effective fireproofing of fuels is about
$4.00 per 100 square feet of application (1982 cost). This figure seems to hold for either Fire-Trol® or
Phos-Chek®.
The hay burning tests, while not able to control all variables, at least gave some indication as to effective
application rates. Based on these tests, the user can expect the following results in fine fuels.
Fire-Trol® 936L Liquid Concentrate
Tests indicate the Fire-Trol® 936L was a successful1 long-term retardant when a mix of 4 gallons of water
to one gallon of retardant (4:1) was applied at a rate of 7 gallons per 100 square feet. The total amount of
retardant in this case was 1.4 gallons/100 square feet. Likewise, it was found that a 2:1 mix was
successful if applied at 3 gallons/100 square feet. In this case, 1 gallon of retardant was spread over 100
square feet. Higher application rates were also successful; lower rates generally were not, although fire
intensity was decreased.
Phos-Chek® GW Powder
This retardant was a successful1 long-term retardant when a 1 pound Phos-Chek® to 1 gallon water mix
(1:1), or a 0.8:1 mix, was applied at a rate of 6 gallons per 100 square feet. This is about 4.6 pounds of
retardant per 100 square feet. Higher application rates were also successful; lower rates were not.
Water Only Treatment
Two facts seem to dominate the results of the water only tests. One: water can produce an effective wet
line, but only for a very short duration; Two: increasing the application rate will not necessarily increase
the time delay effectiveness of water. The surface of fine fuels, such as those used in these tests, will dry
out and allow the fire to escape across the top, even though the underlying fuel has high moisture
content.
The effectiveness of long-term retardant can be very impressive. The cost of the materials and
equipment is also impressively expensive. Reliable application equipment and effective training for the
personnel using the retardants in ground applications is a must. Training and experience will be
necessary for the personnel applying the retardant to know how much is needed for the situation at hand.
1
Successful, defined for these tests, was whether a 3-foot wide retardant line prevented the spread of
fire across the line.
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Most of the objectives stated at the beginning of this test project have been covered; but many aspects of
using long-term retardant on wildfire will have to be addressed by actual experience. Because of the cost
of both retardant and delivery systems, continued research is necessary in order to understand all the
parameters that will maximize retardant usefulness and minimize its effective cost.
Use in field stations should be part of this continuing research. Cautious, limited use of long-term ground
retardant in order to gain further experience seems justified.
CAUTIONS
Retardants are corrosive in nature to many metals. Fire-Trol® 936L and Phos-Chek® GW are formulated
specifically for use with ground tankers. The corrosiveness of these two retardants has been minimized
by the addition of inhibitors. Other users of ground retardant tankers have not considered corrosiveness
to be a problem as long as good housekeeping rules are maintained. This was also found true with the
limited exposure of the equipment during these tests.
Purging all equipment with clear water seems to provide adequate protection for items that are exposed
to the retardant during the application or pumping process. Reservoirs that are intended to store
retardant for extended periods should be made or treated with materials that are impervious to corrosion
from ammonium phosphate. Aluminum, stainless steel and fiberglass all seem to be okay. Plain steel,
coated with galvanized or zinc material, seems to be damaged when exposed to retardant. The
galvanizing material turns black and tends to disappear. How much damage this will cause over a long
period of time has not been determined. However, if the protection of the galvanized material is lost, the
use of water alone will reduce the life expectancy of the reservoir.
If heavily concentrated retardant solutions are pumped, the weight of the material will reduce the
performance of the pump. Fire-Trol® 936L liquid concentrate is approximately 30 percent heavier than
water. Phos-Chek® powder, mixed in a concentrated solution, is also much heavier than water. These
heavy liquids can be pumped, but the horsepower requirement is noticeably increased. The viscosity of
the material does not seem to be a problem.
A Pacific WGC-4 pump was used in conjunction with an eductor to mix a solution of Phos-Chek® GW at a
ratio of 5 pounds to 1 gallon of water (see Diagrams 1, 2, and 3). This mixing system worked very
satisfactorily. As increased amounts of Phos-Chek® was added, it was evident that the horsepower
requirement of the pump engine was also increasing.
The pump shaft seal failed just as the final amount of powder was mixed to complete the 5 to 1 solution.
It is not known for sure, but it is suspected that this failure was due to the increased load on the pump.
Applying retardant solutions of a normal ready-to-use strength should not create a pumping problem.
Transferring heavy solutions to a higher elevation will, however, put an extra demand on the pump.
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