WATER FOG IN WESTERN EUROPE
A 1993 article by Paul T. Grimwood, a firefighter in the London Fire Brigade, discusses a new method of using water fog for interior fire attack.1 This method, developed in Sweden and termed “offensive fog application,” is designed to protect the nozzle team from the dangers of rollover and flashover without the excessive steam production characteristic of the combination method of attack. In his article, Grimwood describes techniques whereby low-volume fog streams are directed into the overhead gas layers using very short-duration bursts or “pulses” of water, intended to cool the combustion gases and reduce internal pressure in the fire area. This action reportedly narrows the flammable range of the gases and reduces the potential for flash-
over without “over-drenching the gas layers” and creating unwanted steam.2
In an effort to convince us that the Swedish technique can work in America, Grimwood provides an example of a recent high-rise building fire in Los Angeles in which an engine company, equipped with the “traditional 2-inch attack line,” was burned as the overhead gases ignited and fire “flashed across the ceiling.”3 The fire building was a modern-generation, central-core high-rise with open-plan floors consisting of 40,000 square feet and packed with plastic furnishings and finishings characteristic of today`s office environment. Grimwood claims that if three 75-gpm fog streams discharging short bursts of water into the gas layer had been utilized in the fire attack, these burn injuries could have been avoided. I believe Grimwood, as well as a large segment of America`s fire service community, has forgotten a timeless truism of firefighting tactics: Big fires require big lines! Over the past few years, several tragic and near-disastrous high-rise fires have occurred in the United States; and, in all cases, one of the primary reasons for the failed fire attacks and large losses were the use of hoselines of insufficient diameter (smaller than 212-inch) and combination nozzles not designed for use with standpipe systems.
Grimwood presents an interesting case, and he describes the Swedish fire, or “flashover,” simulator used to train firefighters in “offensive fog” tech-niques.4 (I have participated in several training sessions in one such unit at the Rockland County, New York, Fire Training Center.) Training under realistic conditions is essential; but, by their very nature, fires created in simulators and laboratories allow us to experience only a small number of the infinite variables present at an uncontrolled fire–the kind fire departments respond to every day. If I am advancing a line down the “long hallway,” I certainly want all the volume and reach I can get as I direct the nozzle “out front and overhead” in a determined effort to knock down the fire and minimize the risk of burns to my fellow firefighters and myself. It is curious to note when reflecting on the merits of the Swedish method that there is a law against excess water damage in Sweden and that ventilation, as practiced by fire departments in the United States, is virtually nonexistent in Western Europe and England. When ventilation is provided, it is usually an afterthought. Grimwood and the Swedes provide an opportunity for thoughtful debate, but I believe that offensive water fog application requires too precise an execution in the very imprecise world of firefighting.5
Endnotes
1. Grimwood, Paul T., “Water-fog in Structural Attack: A European View,” Fire Chief, Aug. 1993.
2. Ibid, p. 90.
3. Ibid, p. 86. The two-inch diameter attack line is not the “traditional” size of handline used by U.S. fire departments.
4. Rockland County does not permit students to handle the low-flow fog nozzle supplied with the simulator, and “offensive fog techniques” are not taught. Students are taught to recognize warning signs of impending flashover and are instructed that, if conditions similar to those inside the simulator are encountered, to open their handlines and darken down the fire using a straight or solid-stream–not fog! (See “Survival Training in the Flashover Simulator,” Gerald Knapp and Christian Delisio, Fire Engineering, June 1995, 83-92.)
5. Grimwood`s article highlights sections of his text Fog Attack: Firefighting Strategy & Tactics, An International View (Surrey, UK: 1992). It is not widely available in the United States but may be obtained from FMJ International, Surrey, U.K.
