Fire ventilation can remove smoke, heat and combustible gases from a structure fire, but you have to do it right. That’s because ventilation introduces fresh air into a structure, which can change a fire’s behavior and even cause flashover and backdraft.
Michael Lee, battalion chief at Mountain View, CO Fire Protection District and safety officer for FEMA USAR Colorado Task Force One, covers the basics of five ventilation methods over at FireRescue1. We should point out that this article isn’t a substitute for proper training. Also, before you use any of these tactics, you should determine how it will affect a fire and make sure everyone’s ready and on board with it.
- Natural Ventilation: Allowing heat and smoke to rise and escape a structure naturally, often through open windows. Lee recommends opening or removing windows, rather than breaking them, and working your way from the top down if you need to ventilate more than one floor with this tactic.
- Mechanical Ventilation: Using smoke ejectors and fans to draw out smoke. Lee recommends placing your fans where they’ll improve natural air flow without pushing smoke into congested areas. You should only use this tactic to boost other ventilation methods, for stairwell ventilation and in confined spaces with knocked-down fires.
- Positive Pressure Ventilation: Using fans to generate positive air pressure in an area to help draw smoke and gases out of a structure. The Venturi effect does the rest, as long as the area has one and only one exit, which must be smaller than the entrance. Lee recommends placing your ventilation opening between firefighters or victims and the fire if you use this tactic.
- Fog Streams: Pointing your hose out a window to ventilate a room. This is similar to positive pressure ventilation as it uses the Venturi effect to draw smoke and gases out of a room. (Our partners at Brotherhood Instructors, LLC demonstrate this tactic with a smooth-bore or solid stream nozzle in this YouTube video) According to Lee, this tactic is only good in the short-term and shouldn’t be used around items requiring protection or in cold or freezing weather.
- Vertical Ventilation: Cutting roof holes above the seat of the fire to let heat and smoke escape. This is a favorite tactic here at Desert Diamond Industries, since we sell blades designed for vertical ventilation. However, it’s also one of the most dangerous tasks on the fireground. To increase your ventilation team’s safety, Lee recommends that they have two exits off the roof, work off of ladders to spread their weight and keep an eye out for signs of unsafe roofs, like spongy material, bubbling tar, melted snow, dry spots on wet roofs, smoke and heat.
FireRescue1, Michael Lee, “The Basics of Ventilation“