Brennan Q&A June 2003

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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.

JUNE 2003

Question: My name is Garrett and I am the captain at a volunteer fire department. Our membership is mostly older guys. We have smooth-bore nozzels on some of our pre-connects and fog nozzels on the others. Most of the guys believe that fog nozzels are better and are more effective than smooth bores. I have shown all types of written materials that have proven differently, but most still do not believe me. I understand that both nozzels have their place, but others don't. Any recomendations to help prove my point?

Answer: Brother, To extinguish fire you must understand fire. Nothing other than charcoal burns in and of itself. Gas is given off by anything that will burn when it reaches its ignition temperature. It is that gas that burns. So . . . extinguishment means that you must cool the product (not the flames) to below its ability to give off the gas (fuel). In the fire service, we do that with water because it is plentiful and cheap.

Enough of the tooooo basic stuff.

An effective hose stream (according to age-old hydraulics and fluid mechanics) is one that will deliver 85 percent of its volume in a 15-inch circle at the point of the flaming fuel source. Water evaporates at a rate dependent on the surface of the water shape exposed. Automatic nozzles are self-inpinging and makes small water droplets — tremendous surface area when compared to the ¾- to 1-micron size of the eliptical ideal drop in the stream. In short, much more volume converts to steam before it has a chance to get to the fuel source. If protection of the advance of firefighters is more important than "making" the seat of the fire and starting water, then automatic nozzles have that advantage. Just an opinion. Remember straight stream IS NOT solid stream!

Write me at my email address, and let me know what you think further on this subject.

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

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