Haz-Mat Survival Tips - Beyond the Rule of Thumb

Survival Tip 8 - Preplanning Foam Fire Suppression Capabilities

By Steven De Lisi

Haz-Mat Survival Tip 7 discussed how first responders, upon arrival at a spill fire involving flammable liquids, can determine the amount of foam concentrate and water necessary to extinguish the fire. Included in these calculations were the dilution ratio for the foam concentrate as determined by the manufacturer of the concentrate, and the minimum application rate for the foam solution (the mixture of concentrate and water) as determined by National Fire Protection Association Standard 11, entitled Low, Medium, and High-Expansion Foam (2005).

While it is beneficial to calculate the requirements for foam concentrate, water, and the minimum application rate upon arrival at an incident, first responders should also be capable of preplanning the maximum foam fire suppression capability of apparatus before an incident occurs. Remember that any attempt by first responders to extinguish a fire that exceeds these capabilities could result in them being unable to gain control of the fire.

Once their foam fire suppression resources are exhausted, the fire may regain its intensity, and if each apparatus that arrives in succession with similar capabilities attempt the same, first responders may never extinguish the fire. Therefore, the critical point is to know when to initiate an attack or to wait until additional foam concentrate and water are available so that first responders can combine their resources to make one uninterrupted and successful approach.


Preplanning foam fire suppression capabilities is based on the premise that fire apparatus may carry only a few 5-gallon containers of concentrate along with 500 to 1,000 gallons of water. Of course, some apparatus may be equipped with built-in foam concentrate storage tanks and additional water may be available from tankers or hydrants. But remember that when operating in areas such as limited-access highways (e.g. interstate routes), hydrants may be scarce and so apparatus preplans should be based on readily available water. When preparing these preplans, the following information is necessary:

1. Foam concentrate dilution ratio (based upon manufacturer's recommendation)

2. Minimum application rate (from NFPA 11, based upon type of foam used)

3. Capacity of water tank

4. Amount of foam concentrate carried

Remember that when using 3% foam concentrate, every 100 gallons of foam solution will require 3 gallons of concentrate diluted with 97 gallons of water. Using this same ratio, 15 gallons of concentrate diluted with 485 gallons of water will produce 500 gallons of foam solution. Remember too that the amount of foam solution needed is based upon a minimum discharge time of 15 minutes at the minimum application rate.

Therefore, if an engine can produce 500 gallons of foam solution, dividing this amount by 15 minutes yields a minimum flow rate of 33 GPM at the nozzle. If the minimum application rate of the foam solution to the surface of the spill fire is .1 GPM for every square foot then 33 GPM will cover approximately 330 square feet (33 divided by .1). This represents an area approximately 20' in diameter or about the size of a modest two-car garage.

Using this scenario, when faced with a spill fire larger than 330 square feet and with immediate access to no more than 500 gallons of water and 15 gallons of 3% foam concentrate, first responders may consider waiting for additional resources before beginning their attack.

While a nozzle with a minimum flow rate of 33 GPM would deliver the required minimum application rate of .1 GPM per square foot for the above scenario, most foam producing nozzles carried on apparatus will have higher flow rates, and thus allow first responders to achieve an application rate higher than that recommended by NFPA 11. However, while increasing the foam application rate above this minimum can reduce the time for extinguishing a fire, it will usually not allow first responders to extinguish a larger fire.
Furthermore, always remember that increasing the dilution ratio beyond that recommended by the manufacturer of the foam concentrate (adding more concentrate to less water) will usually just waste concentrate and reduce your foam fire suppression capabilities.

Haz-Mat Survival Tip 3 provided additional information on foam producing equipment, including inline eductors used to achieve the correct dilution ratio.

Table 1 provides an example of pre-plan calculations using concentrate with a dilution ratio of 3% on apparatus with a 500 gallon water tank. Table 2 provides similar information using foam concentrate with a dilution ratio of 1% on apparatus with a 1,000 gallon water tank.

Table 1
Foam Pre-Plan Calculations for AFFF
Foam Concentrate with a 3% Dilution Ratio / 500 Gallon Water Tank
Concentrate Dilution Rate - 3%
Capacity of Water Tank 500 gallons
Minimum Amount of Foam Concentrate 15 gallons [three 5-gallon containers]
Minimum Application Rate - .1 GPM / sq ft
Minimum Application Time 15 minutes
Maximum Square Feet of Surface Area 333 square feet

Table 2
Foam Pre-Plan Calculations for AFFF
Foam Concentrate with a 1% Dilution Ratio / 1,000Gallon Water Tank
Concentrate Dilution Rate - 1%
Capacity of Water Tank 1,000 gallons
Minimum Amount of Foam Concentrate 10 gallons [two 5-gallon containers]
Minimum Application Rate - .1 GPM / sq ft
Minimum Application Time 15 minutes
Maximum Square Feet of Surface Area 666 square feet

When preplanning foam fire suppression capabilities, be smart, be safe, and remember, everyone goes home!

Discussion Points

1. Determine the dilution ratio(s) and minimum application rate(s) for each type of foam concentrate used by your department. Determine the flow rate of foam nozzles used.

2. Do apparatus in your department equipped with foam suppression capabilities carry sufficient concentrate to be able to use all of the water carried? As an example, does an engine with a 500-gallon water tank have only one five-gallon container of 3% foam concentrate? (Remember that to use all the water available from the tank to create the correct foam solution would require 15 gallons of concentrate)

3. For apparatus in your department equipped with foam fire suppression equipment, preplan the foam fire suppression capabilities of each. Are these capabilities standard?

Biography
Steven M. De Lisi is a 26-year veteran of the fire service and is currently Deputy Chief for the Virginia Air National Guard Fire Rescue located at the Richmond International Airport. De Lisi is a Hazardous Materials Specialist and chairman of the Virginia Fire Chiefs Association's Hazardous Materials Committee. He is also an adjunct instructor for the Virginia Department of Fire Programs and a former member of the NFPA committee on hazardous materials protective clothing. De Lisi began his career in hazardous materials response in 1982 as a member of the HAZMAT team with the Newport News (VA) Fire Department. Since then, he has also served as a Hazardous Materials Officer for the Virginia Department of Emergency Management and in that capacity provided on-scene assistance to first responders involved with hazardous materials incidents in an area that included more than 20 local jurisdictions.

For information on Steven DeLisi's book Hazardous Materials Incidents: Surviving the Initial Response
go to: store.pennwellbooks.com/hamainsuinre.html

Steven M. De Lisi is a 26-year veteran of the fire service and is currently Deputy Chief for the Virginia Air National Guard Fire Rescue located at the Richmond International Airport. De Lisi is a Hazardous Materials Specialist and chairman of the Virginia Fire Chiefs Association's Hazardous Materials Committee. He is also an adjunct instructor for the Virginia Department of Fire Programs and a former member of the NFPA committee on hazardous materials protective clothing. De Lisi began his career in hazardous materials response in 1982 as a member of the HAZMAT team with the Newport News (VA) Fire Department. Since then, he has also served as a Hazardous Materials Officer for the Virginia Department of Emergency Management and in that capacity provided on-scene assistance to first responders involved with hazardous materials incidents in an area that included more than 20 local jurisdictions


Buyers Guide Featured Companies



More Buyer's Guide >

Fire Dynamics

Survival Zone

Extrication Zone

Tech Zone