Every home, apartment, work area and vehicle should be equipped with a fire extinguisher. Fire extinguishers can be purchased at hardware stores or through special fire extinguisher companies. It is a good idea to install them and check them often to make sure they are in proper working order and expiration dates have not expired.
First recognize that there are four different kinds of fires:
Class A fires are ordinary materials like burning paper, lumber, cardboard, plastics etc.
Class B fires involve flammable or combustible liquids such as gasoline, kerosene, and common organic solvents used in the laboratory.
Class C fires involve energized electrical equipment, such as appliances, switches, panel boxes, power tools and hot plates. Water is a particularly dangerous extinguishing medium for class C fires because of the risk of electrical shock.
Class D fires involve combustible metals, such as magnesium, titanium, potassium and sodium as well as organometallic reagents such as alkyllithiums, Grignards and diethylzinc. These materials burn at high temperatures and will react violently with water or other chemicals. Handle with care!!
Some fires may be a combination of these! Your fire extinguishers should have ABC ratings on them. These ratings will often have numbers on them that look something like "3-A:40-B:C". Higher numbers mean more firefighting power.
When you operate an extinguisher, aim the hose at the base of the fire and not directly at the flames. Spray the agent in a sweeping motion until the fire is extinguished. Whether the fire is fully out or not, never, never turn your back on the fire – slowly walk backwards away from the area until you are at a safe distance from the area. Remember to always dial 911!
Types of Fire Extinguishers
Dry Chemical extinguishers are usually rated for multiple purpose use. They contain an extinguishing agent and use a compressed, non-flammable gas as a propellant.
Halon extinguishers contain a gas that interrupts the chemical reaction that takes place when fuels burn. These types of extinguishers are often used to protect valuable electrical equipment since them leave no residue to clean up. Halon extinguishers have a limited range, usually 4 to 6 feet. The initial application of Halon should be made at the base of the fire, even after the flames have been extinguished.
Water These extinguishers contain water and compressed gas and should only be used on Class A (ordinary combustibles) fires.
Carbon Dioxide (CO2) extinguishers are most effective on Class B and C (liquids and electrical) fires. Since the gas disperses quickly, these extinguishers are only effective from 3 to 8 feet. The carbon dioxide is stored as a compressed liquid in the extinguisher; as it expands, it cools the surrounding air. The cooling will often cause ice to form around the “horn” where the gas is expelled from the extinguisher. Since the fire could re-ignite, continue to apply the agent even after the fire appears to be out.