MORE LETTERS
TOM BRENNAN
Readers often e-mail questions to me about structure fire operations. The questions are sometimes basic, but since the basics are the foundation of this column, I will answer some more of the questions here.
What are your thoughts on working close to electrical supply wires on service poles?
New York City had a training bulletin listing how far to keep the aerial (and the firefighter) from service lines, depending on the service voltage (depending on the position of the pole, what section of the city you were working in, what type of occupancy … .) Nonsense! I don`t think the bulletin is in effect today.
Just remember to be aware of the danger high voltage poses to raised and grounded ladders. Perform a risk analysis before climbing them.
I met a firefighter who lost part of his hand from an arc he received from an electrical transformer that was a few feet from him while he ascended an aerial to remove a cat from a tree! How do you feel about the risk analysis of that task?
Basically, a general guide concerning service wires on poles is that the closer you can get the turntable to the wires, the less your danger is. Also, the closer your turntable is to under the wires, the greater the scrub area of the tips of your aerial on the façade of the fire building. Scrub area is the term used to describe the square footage of the building within which the aerial (and therefore firefighter access) can be effective on the façade of the building based on building height and width and aerial truck position. If you are too far outside the wires, a four-story building and its roof could be out of reach for your 100-foot aerial.
If you can find a position for the apparatus that will place the turntable between the line of wires and the building that is your operational objective, you no longer have an access problem because of electrical wires on the service poles. As always, if there is a question of operational safety–and no visible victim–move the aerial to the second-best location.
As an aside, one firefighter in a class I taught asked me, ” … but what if the fire burns through the wires behind you on the aerial, dropping live electrical charges on the grounded truck?” Hmm. I think I will leave the many answers to your imagination.
Do you think that the lack of truck work is contributing to more flashovers?
This was from a firefighter in Pennsylvania who was concerned about the rise in the numbers of flashover at fire scenes coupled with the related firefighter painful injuries and deaths. “Damn right,” is my answer.
Aggressive engine company operations, coupled with proper and effective truck work, will stop almost all flashover conditions from ever becoming events! Period!
Flashover is the product of heating the interior combustibles of any structure to beyond their individual ignition temperatures. THEN, with the addition of air and some high-level “kickoff” energy (the growing lick of live fire), all of the interior combustible surfaces take fire as if all at once. The idea is to cool the heating combustibles to a point at which gases will not evolve from the cumbustibles. This requires early arrival of sufficient firefighting forces to perform entry, search, handline placement and operation, and ventilation. The key is to position operating handlines within the structure to cool the seat of the fire and all the exposures on the interior.
In most cases, this means that the truck work will have to make the enclosure–the fire building–behave itself! Prompt (when effectively possible) vertical ventilation followed by assisted horizontal ventilation ensures the best possible atmosphere for moving the handlines.
As long as staffing reductions continue in the fire service, the cost will always be less and less truck work until it is no longer even understood (sound familiar?) AND an increase in the fire building`s surprise behavior in the forms of flashovers, smoke explosions, and other unaccounted-for rapid fire extension within the building`s operating area.
TOM BRENNAN has more than 35 years of fire service experience. His career spans more than 20 years with the Fire Department of New York as well as four years as chief of the Waterbury (CT) Fire Department. He was the editor of Fire Engineering for eight years and currently is a technical editor. He is co-editor of The Fire Chief`s Handbook, Fifth Edition (Fire Engineering Books, 1995). He was the recipient of the 1998 Fire Engineering Lifetime Achievement Award. Brennan is featured in the video Brennan and Bruno Unplugged (Fire Engineering/FDIC, 1999).
