Fire Extinguishers ABC's
Choosing the right fire extinguisher for you can be confusing because there are so many available and the classifications may be foreign to the normal person.
Everyone should have at least one in their home but which kind do you need? Each kind has it’s own strengths and weaknesses so let’s review the different common categories.
- Class A extinguishers are for ordinary combustible materials such as paper, wood, cardboard, and most plastics. The numerical rating on these types of extinguishers indicates the amount of water it holds and the amount of fire it can extinguish.
- Class B fires involve flammable or combustible liquids such as gasoline, kerosene, grease and oil. The numerical rating for Class B extinguishers indicates the approximate number of square feet of fire it can extinguish.
- Class C fires involve electrical equipment, such as appliances, wiring, circuit breakers and outlets. Never use water to extinguish Class C fires – the risk of electrical shock is far too great! Class C extinguishers do not have a numerical rating. The C classification means the extinguishing agent is non-conductive.
- Class D fire extinguishers are commonly found in a chemical laboratory. They are for fires that involve combustible metals, such as magnesium, titanium, potassium and sodium. These types of extinguishers also have no numerical rating, nor are they given a multi-purpose rating. They are designed for Class D fires only.
Some (especially home) fires may involve a combination of these classifications. Your fire extinguishers should have ABC ratings on them.
The most common types of fire extinguishers are:
- Water extinguishers or APW (air-pressurized water) extinguishers are suitable for Class A fires only. Never use a water extinguisher on grease fires, electrical fires or Class D fires. If you do the flames will spread and make the fire bigger! Water extinguishers are filled with water and pressurized with oxygen. Again- water extinguishers can be very dangerous in the wrong type of situation. Only fight the fire with a Class A extinguisher if you’re certain it contains ordinary combustible materials only!
- Dry chemical extinguishers come in a variety of types and are suitable for a combination of Class A, B and C fires. These are filled with foam or powder and pressurized with nitrogen.
- BC – This is the regular type of dry chemical extinguisher. It is filled with sodium bicarbonate of potassium bicarbonate. The BC variety leaves a mildly corrosive residue, which must be cleaned immediately to prevent any damage to some materials it lands on.
- ABC – This is the multipurpose dry chemical extinguisher. The ABC type is filled with mono ammonium phosphate, a yellow powder that leaves a sticky residue that may be damaging to electronic products such as a computer.
Dry chemical extinguishers have an advantage over CO2 extinguishers since they leave a non-flammable substance on the extinguished material, reducing the likelihood of re-ignition.
- Carbon Dioxide (CO2) extinguishers are used for Class B and C fires. CO2 extinguishers contain carbon dioxide, a non-flammable gas and are highly pressurized. The pressure is so great that it is not uncommon for bits of dry ice to shoot out the nozzle. They don’t work very well on Class A fires because they may not be able to displace enough oxygen to put the fire out, causing it to re-ignite.
CO2 extinguishers have an advantage over dry chemical extinguishers since they don’t leave a harmful residue. This makes them a good choice for an electrical fire on a computer or other electronic device like a radio or TV.
