Investigating Haystack Fires
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Understand the dynamics of spontaneous
ignition, i.e. when and how spontaneous
ignition occurs in haystacks
Understand hay quality, yield and pricing
Determine possible indicators of a spontaneous
ignition fire
Be able to accurately identify a “clinker”
Interview questions
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Exothermic—self-heating
Exothermic Chemical CausationSpontaneous Ignition
Organic Fuel-coal, hay, vegetable or animal
oils, etc.
Microbial-relating to microbes
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Plant respiration—converts plant sugars to
water and carbon dioxide.
Microbial respiration—mesophilic bacteria
ensure continuity of biodegradation (digestion
and decomposition of the organic matter).
Mold respiration—converts plant sugars
•Exothermic Chemical Causation
•Exothermic Biological Causation
•The bursting into flame of a mass of
material as a result of chemical reactions
within the substance, without the addition
of heat from an external source.
•Exothermic Chemical Process
•Theories abound
•Browne
•Rathbaum
•Etc.
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The cut hay is not “dead” and respiration of the
hay continues to occur when moisture content
is between 12%-21%
Microbial respiration generates heat
Heat builds until microbes die—the thermal
death point is reached and heat is generated
faster than it can escape
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The temperature rises above 160°F.
Chemical causation occurs.
Chemical reaction begins to occur and may
sustain itself.
This reaction does not require oxygen, but the
flammable gases produced are at a temperature
above their ignition point. These gases will
ignite when they come in contact with the
oxygen.
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Hays-Timothy, Sudan, Orchard Grass, etc.
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Grass, Legume, Mixed (grass and legume) and
Cereal Grain Straw (oat hay).
Other vegetation residues
Bagasse—sugar cane waste
Coal
Oils-linseed, fish, soy oils, oil stains, etc.
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Oily rags…
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Cut hay must go from approximately 80%
moisture to 22% moisture or less in order to be
stable in storage as baled hay.
The spring season is difficult because of the
higher chance of rain and cooler temperatures
for drying.
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Too much moisture reduces oxygen diffusion
into the haystack
Too much moisture conducts too much heat
out of the stack
Too little moisture stops respiration of the hay
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If hay is stored at less than 12% moisture
content, the respiration often ceases.
Large bales less than 12%
• Small bales less than 18%
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Ideal fuel moisture content for spontaneous
ignition to occur-12% - 21%
Round bales –18%-20%
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Bale density should be at least 10 pounds per
cubic foot to facilitate resistance to weathering.
As bale density increases, the rate at which
moisture and heat escape decreases.
It is critical that dense bales be stored at the
proper moisture (18 to 20 percent or less) so
that risk of spoilage and heating problems are
reduced.
Temperature
Actions
115-130 degrees F
This heat is common. Monitor haystack as usual.
Generally, once heat reached 130, it will begin to
decrease.
130-140 degrees F
Monitor haystack several times each day
150-175 degrees F
Dangerous condition. Microorganisms die. It is
unlikely that the temperature will decrease on its’
own. Ignition of hay is possible if appropriate
actions are not taken. Remove bales, separate and
continue to monitor.
175-185 degrees F
Hot spots and pockets may be expected. Flames
will likely develop when heating hay comes in
contact with the air.
185-212 degrees F
CRITICAL! Temperature rises rapidly above this
point. Hay will almost certainly ignite.
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Take precautions. Pockets may have
already burned out under the hay
surface. Do not attempt to walk on the
hay mass itself.
Temperature
Action
> 115° - 120°
No action required.
When coupled with high moisture, molds
and odors develop and decrease palatability.
> 125°
Heating reduces digestibility of protein,
fiber, and carbohydrate compounds. Forage
quality is reduced. Palatability increases.
> 130° - 140°
Hay is brown and very palatable because of
the carmelization of sugars; unfortunately,
nutritional value is reduced.
> 150°
Hay may turn black, forage quality is greatly
reduced.
Haystack
Temp
Actions
Forage
Quality
Actions
115-130
Common heat. Monitor as
usual.
>115-120
No nutritional value loss
>125
Forage quality is reduced.
Palatability increases.
130-140
Temperatures can rapidly
increase.
>130-140
Hay is brown and very
palatable. Hay loses value.
150-175
Dangerous condition.
Microorganisms die.
Ignition of hay is possible if >150
appropriate actions are not
taken. Remove bales,
separate and continue to
monitor.
Hay may turn black.
Value greatly decreased
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Generally speaking in my area…
Because the highest yield of the season is on the
first cut, it takes longer for the hay to dry just
due to the bulk.
33% to 40% of the total yield for the year is
from the first cut.
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Higher yield equates to lower forage quality-1st cut
Higher forage quality produces lower yield-2nd cut
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Large Square Premium $260.00-$280.00
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Good/Premium $240.00-$250.00
Good $225.00-$265.00
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$275.00 Export
$240.00 Export
Fair $200.00-$200.00 (Rain Damage)
Utility $170.00-$185.00 (Rain Damage)
 October 21, 2011 Washington-Oregon Weekly Hay Report
1st Cut
Premium
Good
Fair
Utility
5tpa x 200 ac @
$275.00 per
ton=
5tpa x 200 ac @
$225.00 per
ton=
5tpa x 200 ac @
$200.00 per
ton=
5tpa x 200 ac @
$170.00 per
ton=
$275,000
$225,000
$200,000
$170,000
2tpa x 200 ac @
$225.00 per
ton=
2tpa x 200 ac @
$200.00 per
ton=
2tpa x 200 ac @
$170.00 per
ton=
$90,000
$80,000
$68,000
2nd Cut 2tpa x 200 ac @
$275.00 per
ton=
$110,000
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Moisture Meter—Gauges moisture content of
the loose or baled hay.
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Caution! Even properly calibrated and used
according to their manufacturer’s instructions, hay
moisture meters are accurate to approximately +/- 4.
The only accurate method for estimating bale
moisture is to dry the forage down.
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Heat Probe—Gauges heat in middle areas of
the stacks.
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Generally found towards the middle of the
stack, not at the very edges
Grayish, greenish, black, glassy
Oftentimes significantly heavier than it
looks
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The Inorganic Residue of the plant stems
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Sodium Oxide-used in ceramics and glasses
Calcium Oxide-thermal decomposition
byproduct
Silicon Oxide-principal component in glass
Other Trace Elements
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Almost all natural elements contain
calcium, magnesium, sodium, silicon, etc.
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Qualitative analysis—gives the properties
found within a substance
Quantitative analysis—gives the percentage
of each item (amount of item in sample as a
whole)
Fire Debris Analysis—Gas chromatography
with mass spectrometric (GC/MS) detection
Labs also perform Elemental Analysis for
this type of sample
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Hands-on examination of specimens
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Note Colors, Weight, Appearance
Not every sample is a clinker!
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Moisture content of hay when it is put up
Pile size
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Hay insulates, so the larger the haystack, the less
cooling there is to offset the heat.
Packing density of the hay
Ambient temperature
Outside introduction of moisture
Length of time the hay has been baled and
stacked
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10-15 days after stacking
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Haystack fires may occur as soon as 6 days after
stacking (under ideal circumstances)
May occur months after stacking
As long as plant respiration can occur,
spontaneous ignition is plausible!
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Eyewitness accounts of a sharp/acrid/caramel
odor, or burning tobacco smell prior to the fire
Spotting or discoloration of the hay
Adjoining haystacks with spotting or
discoloration
Slight vapor or smoke coming from the stacks
Temperature readings between 150-175 degrees
prior to the fire
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Eyewitness testimony of a fire starting in the
“middle” of the stack
History of high moisture content in the stacks
(greater than 18%)
Laboratory report
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Where was the fire located in the stack?
When was the hay cut?
Was this hay from a first cut or 2nd/3rd cut?
When was the hay baled?
Has the stack been moved or manipulated in
any way?
Were temperature probes conducted on the
stack?
What temperatures were noted?
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Were moisture probes conducted ? Was there
above average moisture content in the hay?
What size were the bales?
Was the hay under a tarp? If so, color of the
tarp.
Did anyone notice any unusual sweating or
browning of the hay?
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Was there an unusual odor noted around the
stack?
Was the hay sold?
At what price was the hay sold?
What is the current price of hay?
To whom was the hay sold?
How long has the hay been stacked?
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What year was the field seeded?
How “old” was the hay field? (1-5 years, more
than 5 years, etc.)
What are the confirmed crop yields for the past
5 years?
Is there a history of crop infestation?
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Mealybug, Spider Mite, Thrips
Have there been previous claims for fire losses?
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When and under what circumstances?
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What type of equipment is routinely used in
the operation?
Who was running the equipment?
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Was the hay treated? With what?
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Hay treated with preservatives containing
ethoxyquin and BHT (butylated hydroxytoluene)
produce hydrogen cyanide gas at around 240
degrees (115 degrees C).
There are numerous treatments out there
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Perimeter examination of haystack
Consistent, systematic dig out of scene
Any potential evidence located, proceed as
with any investigation
Haystack fire by-products mimic clinkers—
Don’t be fooled!
Brenda Larsen
Kittitas County Fire Marshal
509-962-7000
brenda.larsen@co.kittitas.wa.us