Brennan Q&A November 2002

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TOM BRENNAN has more than 35 years of fire service experience having responded to 33,000 fire alarms. His career spans more than 20 years with the Fire Department of New York as well as four years as chief of the Waterbury (Conn.) Fire Department. He has a bachelor of science degree, summa cum laude, John Jay College; Alumnus of the Year Award, John Jay College; chairman of the Connecticut Fire Chiefs Association and a charter member of the National Fire Protection Association, Fire Service Section. He has delivered courses and seminars throughout the United States and has instructed at the National Fire Academy. He was the editor of Fire Engineering Magazine for eight years, is currently a technical editor, and his column “Random Thoughts,” is a regular monthly feature. He is co-editor of The Fire Chief’s Handbook, Fifth Edition. He is the recipient of the 1998 Fire Engineering Lifetime Achievement Award.

NOVEMBER 2002

Question: I have been meaning to write to you about roof cutting since your September entries in Fire Nuggets: Question and Answers. My question is two fold: A. When do you cut a second hole in a roof assembly? B. If you don’t, why not?

Answer: I have a short and a medium answer for your two questions (hoping to hear more from you or our other readers).

First, I cut the second hole at the next top-floor fire at which I am assigned vertical ventilation!

Second part: A ventilation hole cut into a roof under which there is fire has one main purpose other than letting the fire out. It severely halts the pressurized horizontal spread of flame and heat in the space into which the hole is made. THEN it begins to pull the spreading flame back into itself and, along with it, all the byproducts of the (up-to-now) enclosed space that is burning.

If you made your first ventilation hole in a location as close as safety and risk analysis allow, that is great. The fire knows where you are and will be trying to get there. The next best thing you can do is to make THAT hole bigger! The only way you can do that, if the vent hole is “doing its job,” is to have prepared to make the hole bigger before you pulled the roof sheathing and pushed the interior membrane down and out of the way.

If you make a hole somewhere else — or another team of nitwits begins a hole remote from yours, you will certainly confuse the fire and its behavior. With the additional ventilation, the fire will spread into larger areas and certainly areas that would never have burned in the first place. If there are operations going on below, such as search, extinguishment, overhaul, rescue/removal, and more, you will cause unnatural fire behavior to the consternation of others involved in risk analysis and, in some cases, there will be catastrophic results!

There is certainly a lot more to say on this subject, but this is enough for now.

P.S. If you are reading this, write a few words or more.

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Write if you agree or don’t agree or on anything. Tbrennan@firenuggets.com

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