# Foam Calculation

```Foam Application Rates for
E85 and E-95
Application Rates
Described in Terms of the Amount in Gallons of
Foam Solution Reaching the Total Square Footage
of the Fuel Surface Every Minute
• Critical Application Rate - lowest rate at which a foam
will extinguish a fire under a particular set of ideal
conditions (.06 for gasoline)
• Minimum application rate - the amount found by tests
to be the most practical in terms of speed and control of
agent required
Application Rates
Foam concentrate application rates may be as
low as 0.06 gpm for gasoline to as much as 0.20
for polar solvents (ethanol).
Minimum foam concentrate
application rates.
Application rates are listed as gpm
• .10 for flammable liquid spill/fire
• .16 for tank diameter of less than 150’
• .18 for tank diameter of less than 200’
• .20 for tank diameter of less than 250’
• .20 Polar solvent spill/fire
Polar Solvent = Ethanol
NFPA 11
“Tests have shown that foam may
travel effectively across at least
100 feet of burning liquid surface”.
“Sometimes”
Application Rates Calculated
1. Determine Area of Hazard
2. Choose Appropriate Application Rate
3. Rate x Area = GPM of Foam Solution
4. Solution GPM x % Used = Concentrate GPM
5. Concentrate GPM x Time = Total Concentrate
• Storage Tanks - 60 Minute Flow Time
• Spills - 15 Minutes Flow Time
Application Rates Calculated
Example
• Determine Area of Hazard = 3000 sq. ft
• Application Rate = 0.20 GPM
• Rate x Area + 600 GPM of Solution
• 600 GPM x 3% Used = 18 GPM Concentrate
• 18 x 15 minutes application time = 270 gals
needed
This calculation example is based on a spill area
of 75’ x 40’.
Requirements
• Based upon the 75’ x 40’ spill footprint one
can see that 270 gallons of 3% foam
concentrate would be needed.
• If we assume every gallon of 3% foam
concentrate requires 97 gallons of water,
we can see that we would also need
26,190 gallons of water (97 x 270) to
maintain the required 15-minute
application period.
Preplan
Based upon the previous example:
• Where would you get 270-gallons of 3%
AR-AFFF concentrate?
• Where would you get 26,190-gallons of
water in an area without hydrant’s?
Quick Foam Flow
Work Sheet
1. Determine Area of Hazard* = SQ. FT.
* (L x W) or (.785 D2)
2. Choose Application Rate =
3.
4.
5.
Sq. Ft.
X
GPM
X
Flow rate of solution
Gallons
GPM
GPM
=
%
% of FLC
GPM
=
Gallons
Gallons of FLC per/minute
Minutes
Gallons
X
=
Gallons of FLC per/minutes Duration of flow Total FLC Required
• NFPA 11 states that a minimum15-minute
flow duration is required.
• If you calculate this minimum requirement in all
of your foam concentrate requirements this
should get you off to a good start.
• Do not hesitate to calculate more if there is a
large spill or fire.
• Gasohol (not E-95 or E-85) fires may be
extinguished using conventional AFFF and ARAFFF but increased application rates may be
necessary especially for prolonged burn back
resistance.
```