FF training, 2nd module

Tuesday night was the start of the 2nd training module, Fireground Support. (Sorry I didn't post about it sooner...) Tuesday was a lecture, on fire behavior.

Without meaning to, in my last post, I talked about much of what we covered, with fire classes, and the ways of putting each out.

We also talked about heat: convective, radiative and conductive.

There's conduction, i.e. why the handle on a pan on the stove gets hot. Heat travels along material, and the more dense the material, in general, the better it conducts heat.

Convection is the whole hot-air-rises thing, only in fires, (especially in a confined space) it's much more pronounced. Fire greatly heats air, which rises and spreads out. (This is why FF's often crawl: to stay out of the hot gases that rise to the ceiling, not to mention staying out of the smoke and other toxic stuff that's up high.) In a multi-story fire, the hot gases can "mushroom". A fire on the first floor can generate hot gas that rises and fills first the fourth floor, then third, then second and finally first.

We touched on the need for ventilation: to get rid of the hot gases and make the interior safer for FF's and any trapped victims. But it's important to ventilate in the right place. Ventilating up (i.e. opening up a hole in the roof) can be much better than opening (i.e. breaking) a window, as opening a window will allow extra/excess oxygen to enter the building, and will draw the fire towards that window. But there are times when that can work to your advantage, if the opening you're creating is near the fire, and can serve to hold the fire at that location. Later modules will cover this in greater detail.

Then there's radiation (i.e. how the sun heats the earth). A fire will give off lots of radiant heat, which will heat materials around it. A fire in a corner will spread faster than a fire in the center of the room, partly because of proximity to fuel (i.e. curtains, paneling, etc.), but partly because any wall materials will absorb and re-radiate the heat given off by the fire. A fire can spread from one house to an adjacent building strictly by radiation. (On the recent fire near us, that I was on standby for, the neighboring house had its siding melted by the heat of the house fire; one fire company task is "protecting the exposures", or making sure that such adjacent properties stay cool enough to not combust.)

Last night was all about fire extinguishers. They're rated for certain classes of fires, with the most common ones being for Class ABC or Class BC fires. There are also Class D dry powder ext's for use on metal fires, but they'll most likely be found in industrial settings where those metals are more likely to be found. It's quite important to use the right ext. for your class of fire, as the wrong one can make things much worse (i.e. pressurized water on a metals fire or liquid fuel fire can cause an explosion).

Common ext's are dry chemical or CO2, with Class A pressurized water being available as well. Fire apparatus need to have a wide variety of ext's, and will probably have most or all of the above mentioned types.

Operating one is done by the acronym "PASS": Pull the pin, Aim the nozzle at the base of the flame, Squeeze the handle and Sweep the nozzle over the fire. You do want to be careful, though, as you're aiming at the base, to not shoot the material INTO the fuel (esp. on a liquid fuel fire), or you'll just spread the fuel around, making things worse.

The highlight of last night, though, was getting to put out a fuel oil fire with an ABC dry-chemical extinguisher. I got picked to go first out of the 20+ FFs, got the fire out in short order, and then found that my (old, ready-to-be-scrapped) ext. wouldn't turn off. There's not much material in one, so it didn't go on for long, and finally I was told to turn it upside down, which vents the propellant w/o spraying much powder. Then, after everyone got a chance, some of us went a 2nd or 3rd time. The fire was in a pan, with water being put in first, then a layer of fuel oil that the instructor lit with a road flare. (Somewhat surprisingly, it took a bit of time to get the oil hot enough to burn; it didn't just catch right away the first time. After it got hot from the flames, it was easier to re-light, though.)

Coming up in the next couple of weeks will be water supply (i.e. working w/hydrants) and hoses (hooking them up to both hydrants and engines). Looking forward to it all.