Pressure ventilation vs. Class A foam

Many firefighters have been killed and injured throughout the years while ventilating structures. Class A foam has changed the need for or possibly even the priority of ventilation. We have trained municipal firefighters throughout Canada during the past six years, as we introduced FoamProt and Silv-ext Fire Control Concentrate into their arsenal of tools. Therefore, we write from experience derived from training house burns and ongoing firefighting operations after the introduction of the Class A Foam Application Concept. We supply this information with the hope that fire authorities with Class A foam firefighting capabilities will test the practice and realize that the heat in the structure can be turned against itself. Most importantly, it will contribute to saving firefighters` lives.

Why ventilate and place firefighters at risk to remove the heat, the very essential product necessary to improve the performance of water when applied to confined spaces? Because applying plain water into structures has never been effective in quickly controlling the fire.

The Swedes have been engaged in developing water misting for the past several years, and the Brits have recently conducted tests that confirm that small water particles are effective on fires in confined spaces. The thrust of this program is to expose as large a surface area of water to the heat through the production of smaller water droplets. North American-designed water fog nozzles develop drops of water.

The Class A Foam Application Concept we have introduced is based on the same philosophy as the “water misting” application. The difference is that we expose more water surface area to the heat in a confined space through the generation of “bubbles” instead of smaller droplets of water.

Can you imagine attempting to market a nozzle that generates smaller droplets than a North American-designed water fog nozzle? It is difficult enough convincing fire authorities that water is not free and the millions and billions of gallons of water consumed annually can be more effective if applied at one-tenth the application rate using Class A foam.

In other words, the water fog nozzles used in North America cannot develop the small water droplets generated by the Swedish nozzles. So through the generation of bubbles, we expand the linear surface area of the applied water to a heated compartment five to 10 times the surface area, compared with the water drops of a standard water fog nozzle.

Through the induction of Class A foam into the water stream, we go one step further than water misting through smaller droplets. Foam bubbles expose the water to the heat of a compartment fire using a thin film of water. Through the application of the film of water, 100 percent of the applied solution will be converted to steam. More importantly, a “wet water steam” that will bond to carbon fuels and penetrate deep-seated fires is developed. Also, using Class A foam for compartment fires involves a simple application technique similar to the present water fog nozzle application.

To understand the application technique, we must first explain the simple philosophy of what occurs in a fire, because we observed while making our presentation over the past 16 years that many firefighters concentrate on the surface fire and not on what is contributing to the continued development of vapors in the fires.

Structure fires do not spread horizontally across the floor of a structure. A fire is ignited in the Class A fuel. As the fire increases in intensity, the heat rises, spreads across the ceiling, and then spreads throughout the room as a result of the “heat sink” that radiates down onto the other fuels in the compartment. As these fuels are raised to vapor pressures, they ignite.

Ventilation, as we learned many years ago, removed the hot toxic gases and reduced the risk to firefighters attacking the fire. Pressure ventilation increased the speed at which ventilation could be accomplished with a mechanical blower ….

Class A foam applied into a compartment fire generates a wet water steam cloud that will travel throughout the structure on the heat convection developed during the fire. It will travel from compartment to compartment horizontally and vertically, displacing oxygen and bonding it to carbon fuels throughout the structure; penetrate deep-seated fires; and control the spread of fire by placing a “wet water film over the fuel surfaces.”

Ventilation … was developed … to reduce the risk to firefighters …. The risk may be reduced, but it is not eliminated because we continue to place firefighters in precarious locations to cut holes in structures or break windows to exhaust the hot gases by natural or pressure ventilation …. Why cut holes in a structure unnecessarily? Firefighters are accused of doing more damage than the fire through cutting holes and pumping water …. Ventilate after the Class A foam attack to displace the white steam cloud if rescue is necessary.

We have learned through experience that when used properly the heat generated before the arrival of firefighters can be turned on itself to control and extinguish the fire, thus reducing structure damage through cutting holes in roofs and walls, breaking windows, and applying water as long as black smoke continues to emit from the structure outlets.

Think the fire triangle: fuel, oxygen, heat. Heat rises–by applying films to water (bubbles) across the ceiling to generate the wet water steam cloud, the heat is consumed. Fuel–Wet fuel cannot burn. Plain water cannot penetrate carbon fuel. Wet water solution bonds to carbon fuel, increasing moisture content. Extinguishing deep-seated fires. Oxygen–Foam bubbles are used to generate volumes of steam-displacing oxygen. Bubbles bond to Class A fuels, separating oxygen and holding the water in place until the solution penetrates through the carbon fuel layer.

Editor`s note: The author is a 44-year veteran of the fire service and has been a firefighter, a chief, and fire marshal. He is the co-inventor of Silv-ext Fire Control Concentrate (Patented) and Scottyt. Firefighter Products (patented) and a consultant for various government agencies in the United States and Canada and has served on various committees relative to the use of Class A foam. He may be reached at (613) 238-1325 or by fax (613) 230-6074.