The Types of Fire Classifications & How To Control Them

Posted by Lee Kaiser on Feb 16, 2021 4:00:00 PM

Do you know the difference between fire control and fire suppression? How about the different types of fires (and their classifications) that are possible in your facility? In the video below, ORR VP of Engineering Lee Kaiser explains what fire control is, how it differs from fire suppression, and the different types of fire classifications to be aware





Video Transcript

Lee: "Let's dive in and start talking about suppression systems, and to get everybody on the same page, we're going to do a little vocabulary review with regards to suppression. By a show of hands, when I say a suppression system, who thinks that means sprinklers? Raise your hands. A couple people think that.

Suppression is sort of a bucket list term. With suppression, there are different levels of performance and performance expectations that we should have for a suppression system, and it breaks it down to this. Fire suppression is one of those.

Fire Control

Fire control is one performance expectation where we limit the size of the fire within the compartment that it started in to decrease the heat release and pre‑wet adjacent combustibles, so that's what sprinklers do. They limit the ceiling gas temperatures, and they pre-wet things that haven't burnt yet so they don't burn. We expect that with a system that has fire control there should be, or could be, some manual firefighting that needs to occur to completely extinguish that fire that's occurred.

Fire Suppression

The next level is fire suppression, where we've got a sharp reduction of the heat release rate, lowering it just to glowing combustion. If we've got a solid material that's burnt for a little while, we release the suppression system, and we expect suppression. There will be some manual firefighting that needs to occur just to stop that glowing combustion. A lot of times the expectation for a suppression system is extinguishment.

That's where we completely extinguish any combustion mixture, that there's no combustion that needs to happen, no manual firefighting, just a little investigation. Is it put out after the system is discharged? So as we talk about specific suppression systems this morning, the different applications can have a different performance expectation, so it's important to define those.

Fire Classifications

The fire classifications and different things that can burn. This is going to be a review for a lot of people, but it's important for those of us that aren't familiar.

Class A fires are ordinary combustibles: wood, paper, plastic, those types of things we expect normally to be combustible and burn.

Class B fires are now flammable and combustible liquids and flammable gases, and so some suppression systems work to extinguish Class B type fires. We see a lot of Class B hazards in manufacturing and industrial, not normal types of spaces where we'd see Class A fires.

Class C fires can occur in a lot of different places, usually around electrical equipment. A Class C fire is a fire that's electrically enhanced, or sometimes I say an electrically commutated fire. There's an arc, some sort of short or arc due to a malfunction in some electrical equipment, but that's a sustained arc. That arc is an ignition source, so any combustible materials around it have that sustained ignition source, and therefore Class C fires are typically harder to extinguish.

Even though we can put out the fire, there's that continued electrical arc to keep things going. One of the traditional ways to help control a Class C fire is to shut off the power to that electrical equipment causing the arc, and then once that arc is removed a lot of Class C fires become Class A fires and are much easier to extinguish.

Class D fires are something that we don't talk about a lot. They're not that common. Class D fires are fires that occur in combustible metals. Let's see our list here: magnesium, sodium, potassium. How about aluminum, titanium? Those metals, when they're in a fine form, like chips or powdered form, are combustible, and they're really hard to put out, because water won't put that type of fire out. In fact, water makes it worse. As we talk about suppression systems, for a long time we haven't had many options, but we do have some options today that are just being developed. We'll spend a little time talking about those when we talk about clean agents

Class K fires is the last one, so cooking oils and fats. Every restaurant you go into probably has a wet chemical hood system in there to extinguish a fire at the fryer or the grill, and are fairly common."

Topics: Fire Protection Services, Fire Protection Systems, Nationwide

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