Control Flammable Liquid Fires by “Premixing”

Control Flammable Liquid Fires by “Premixing”


Every firefighter faces the eventuality of a flammable liquid fire. Firefighters experienced in this type of fire and its suppression agree that the rapidity with which fire progresses in liquids is amazing. The intense Btu (British thermal unit) production signals to firefighters the importance of rapidly containing and extinguishing the fire. Improper initial actions will demand the cost of many long and hazardous hours at the incident. Well designed specialized flammable liquid suppression equipment is, of course, desirable, but unfortunately not affordable by many communities.

Because flammable liquid fires are not a routine occurrence, emergency organizations, out of need, tend to specialize. An example of such specialization is aircraft fire suppression. Aircraft fire protection organizations are obviously prepared to attack and extinguish flammable liquid fires because they present the basis for much of the aircraft fire suppression needs.

Structural fire suppression organizations, however, are not prepared to provide an immediate and aggressive attack on the flammable liquid incident because of inadequately designed equipment. In fact, some communities rely on aircraft firefighting organizations for their primary means of extinguishing flammable liquid fires. While this is usually done out of necessity, it does not provide those first arriving structural firefighters with the meanfe of attacking the smaller, fast-developing flammable liquid fire. This often results in extreme frustration for the firefighters and can lead to ineffective and “catch-up” tactics.

Various attempts have been made to deter this deficiency. Some structural fire suppression organizations issue containers of foam and one or more in-line eductors to their firefighting units. Others engineer specific pieces of apparatus for foam operations. While all of these alternatives are credible approaches, the final result is, again, that many first arriving firefighters do not have immediate access to a process needed to contain or suppress flammable liquid fires.

A simple, yet effective method that every community with a pumper can use to quickly attack flammable liquid fires is to simply dump AFFF into the booster tank of the apparatus.

Eductors have often been the source of frustrations. Clogged valves, excessive hose lays, and problems caused by extreme elevations are but a few of the inadequacies of eductors. The best solution is to purchase or design an apparatus for foam usage. However, this is not always a viable option for numerous departments because of the cost factor and the many pieces of fire apparatus with no such foam capabilities that have already been purchased.

There is a simple, yet effective method that every community with a pumper can use to quickly attack flammable liquid fires. Why not carry two or three five-gallon containers of Aqueous Film Forming Foam (AFFF) on each engine and, when needed, simply dump it into the booster tank of the apparatus? This is often referred to as “premixing.” Although the term “premixing” tends to indicate that an extensive amount of time is necessary to mix the solution with the contents of the booster tank, this is a misconception. The mixing is almost instantaneous. The Fort Worth, TX, Fire Department, and many other fire departments, have used this process for some time. While realizing this technique is inferior to having specially engineered apparatus with foam capabilities, we in Fort Worth have successfully used the dumping or premixing technique on numerous occasions.

The advantages of this procedure are as follows:

  • No special equipment is necessary, other than the AFFF solution.
  • There are no additional expenditures other than the AFFF.
  • It is a fast, simple, yet effective procedure.
  • Regular nozzles and hose lines, currently described in your departmental procedures, are utilized.
  • There are no additional hydraulic formulas necessary. Just as in any foam attack, apply the agent in a “gentle manner.”
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  • AFFF has a cleaning effect on the pump.
  • The premixing of AFFF does not require exact percentages or calculations.
  • This technique provides immediate foam capabilities for every engine company.
  • There are a few disadvantages:
  • Some may believe the technique is wasteful. That is, use two or more five-gallon containers of AFFF to premix approximately 400 gallons of foam, and then use only a small portion of the contents.
  • If some of the AFFF solution is spilled and allowed to get under the apparatus paint, some paint peeling will occur.
  • Some believe exact percentages are necessary in order to extinguish flammable liquid fires. (Our experiences in both training fires and actual emergencies have not shown this to be true.)
  • Some express concerns about the effect of AFFF on the internal components of the pump. Those who share this concern should contact their local AFFF dealer and request a written opinion. Remember, we are premixing AFFF. We. are not premixing protein or other chemical types of foam solutions.

Considering conditions under which departments often operate, premixing is an alternative tactic.

Again, dumping or premixing may not be the best method of developing and applying foam solutions. However, considering the circumstances under which most structurally oriented departments must operate, this procedure may be the best alternative. Build some training fires and try it. Perhaps by “dumping it” your department will have a suppression capability not previously considered for your first arriving units at a flammable liquid incident.

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