Fire Safety, Part 1: About Fires and Fire Types

A general note on fire safety:

If your clothing catches on fire, it is a natural response to panic and run to the nearest shower or fire blanket. Don't do it! Running will just fan the flames and increase the potential for serious injury. The correct response is to

Stop, Drop, and Roll

on the ground to extinguish the flames. Cover your face with your hands to protect your face and lungs. If one of your colleagues catches fire, panics, and starts to run, tackle him or her and smother the flames.

The information given here is intended as an introduction to fires and fire extinguishers. It is not a comprehensive reference. Be aware that fires are dangerous, and many aspects of fire safety are not discussed here. For more in-depth information and hands-on training, contact your local Fire Marshal's office.


Combustion

Combustion is a chemical reaction in which a fuel is rapidly oxidized. Three things are required to sustain a fire:

Therefore, to kill a fire, you must deny the fire one or more of these three things. You may:


Types of Fires

There are four classes of fires, categorized according to the kind of material that is burning. For the first three classes of fires, there are two sets of color-coded icons in common use. One or both kinds of icons appear on most fire extinguishers to indicate the kinds of fire against which the unit is intended to be used. There is only one icon used to indicate the fourth (class D) kind of fire. Class D fires involve uncommon materials and occur in fairly specialized situations. Note that any given fire can fall into more than one class; a fire that involves both burning paper and kitchen grease would be a Class AB fire.

[green triangle with letter A] [green icon with burning wood, paper] Class A fires are those fueled by materials that, when they burn, leave a residue in the form of ash, such as paper, wood, cloth, rubber, and certain plastics.
[red square with letter B] [red icon with burning liquid and gasoline can] Class B fires involve flammable liquids and gasses, such as gasoline, paint thinner, kitchen grease, propane, and acetylene.
[blue circle with letter C] [blue icon with burning electrical socket and cord] Fires that involve energized electrical wiring or equipment (motors, computers, panel boxes) are Class C fires. Note that if the electricity to the equipment is cut, a Class C fire becomes one of the other three types of fires.
[yellow 5-pointed star with letter D]   Class D fires involve exotic metals, such as magnesium, sodium, titanium, and certain organometallic compounds such as alkyllithium and Grignard reagents.

Fire Safety, Part 2: Putting Out Fires