VideoJug.com - Fire Terminology And Science

VideoJug: Fire Terminology And Science

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Fire Terminology And Science
What are the different classifications of fire?

The four classifications of fire are A, B, C, and D. Class A fires are your combustible, or ordinary combustibles such as paper, wood, plastic. Your Class B fires are your flammable liquid fires. We are talking gasoline, diesel, oil here. Indeed it's cooking oil, primarily, and these types of substances. Class C are your energized electrical, such as an appliance that's plugged in, and has a power source that catches on fire, these would all be a Class C fire. When we remove the source of energy, it becomes a Class A fire, with just an ordinary combustible. And then we have Class D fires, which are what we call combustible metal fires. So metals ending in ium such as aluminium, titanium, magnesium. This is why often, when we ask someone if they had a fire, what kinds of things would they put on the fire if they didn't have an extinguisher, you'll get a real spectrum of answers. But one of the answers that you definitely want to educate on, is they'll say that you can throw salt on a fire. Salt is a combustible metal, because it's sodium chloride. We don't think of it in terms of that, but it actually can intensify the fire.
What does 'fire retardant' mean?

A fire retardant is something that we use to coat a material to lessen the chance of it becoming fully engulfed in flames. What it does is put a barrier on that particular material and it makes it much more difficult for the actual heat to penetrate whatever that material is. Commonly, if we look at clothing, that's one of the things that I think we as consumers would see. Looking at a label, especially if your buying clothes for children, you want to make sure that fire retardants are used. Again what it does is it makes it more difficult for that particular material to catch on fire.
What is a fire 'flashover'?

The primary material that is on fire is generating a lot of heat and as it's doing that it's giving off gasses. In that confined space or that area where the fire is occurring, it's then heating up other pieces of furniture or other materials, and then those in turn begin to give off gasses as well. These gasses all come together and physically what would happen is that as a fire fighter you'd be in there and you'd start looking at characteristics that would change such as dark smoke. You'd see an intensification of heat in the area and these are all those things that are pointing to the fact that this flashover is going to occur. Really what happens is that the flames will come up from behind you and end up going up a wall and over a ceiling. If you could see it, it would be like little fingers over your head. That's really what a flash over is. it's when all those gasses heat to a certain degree and it starts to fill the room and it starts to overcome and engulf you, that would be an easier way to put it.
What is a fire's 'ignition point'?

Materials will have a particular degree in which they are going to ignite, as far as fire is concerned and this is their ignition point. When materials reach that level of intensification with the heat in the room and the gases and such, there's a flash point or an ignition point rather, and that particular material will catch on fire. The ignition point is not really spontaneous combustion but it's similar. In other words, it has to get to that intensification and then, in fact, it will ignite and start to burn.
What are fire 'hot spots'?

Fire hot spots we usually see when we have brush fires or wild land fires. Or actually we have a lot of structures that are on fire and what happens is, fire generates it's own wind and so, as the products are burning, lets say the roof of a house and some of the older homes that still exist here have the wood shingle roof, and when that catches on fire the winds catch it and the embers end up flying hundreds of feet away and then they will ignite another area. They will ignite another little spot of brush or another material, whatever it might be, but those are the little hot spots that happen which are largely due to flying embers, these are what we refer to as fire hot spots.
What is a fire 'backdraft'?

A fire back draft can best be described in terms of most of us probably saw the movie Back draft, and you know one of those great lines in that movie was, "Timmy did you check the door before you opened it up and just got blown down the stairwell?" The fire back draft happens when inside that room the fire is happening, and it has consumed all of the oxygen in that space. So what it does is, if we look characteristically, if you were outside of a room that had windows that was on fire that was in a back draft situation, it would almost look as though the room was breathing. The windows would actually expand and contract a little bit. Very dark smoke would kind of seep out of from under the door a little bit and suck back in. And that right there is the fire back draft, it's lost all of the oxygen left in that space and now its looking for more so that it can continue to burn. So, consequently, what could happen is when you open a door or a window, you introduce that oxygen and it is potentially just going to be a very explosive reaction. The windows will blow out, the door will blow open, and if you're standing there, you're going to be blown a pretty far distance from that door due to the fire back draft.
How hot can a room get if it is on fire?

With the fire itself when it first starts, the heat is not too bad, but really on the upper end, by the time it reaches the ceiling, it is over 1,000 degrees easy. Of which you would never be able to stand in there and sustain the heat, especially if you did not have any protective clothing. Even as fire-fighters we have turn out clothing that is flame retardant, we have breathing/air tanks and so on that enable us to stay in that environment, obviously much longer than just an average person but the heat is unbelievably hot and you feel it even through the clothing and the areas that are not protected as well like your cheeks or your nose. Indeed even though it is under the mask you still feel that heat. Your ears as well, these are some of the areas that would commonly see fire fighters get burnt on, especially the ears, because of how hot a room gets if it is on fire.