Chemicals Used in Fire Extinguishers

Fire extinguishers save lives. Through proper training, a well-positioned fire extinguisher can prevent a fire from getting out of control. The chemicals that comprise each extinguisher are based on the extinguisher's purpose. With the addition of foaming material, water or carbon dioxide, these chemicals are effective in squelching flames.

History

• According to the Independent Fire Safety Advice Centre (IFSAC), one of the first components of a fire extinguisher was water. A man named Ctesibius is credited with inventing a hand pump to spray water on fires around 200 B.C. It was not until 1819---when Capt. George William Manby used a compressed potassium carbonate solution to fill portable extinguishing devices---that a fire extinguisher contained anything other than water.

  In the late 1800s, a sodium bicarbonate and water mixture fueled some extinguishers. In 1912, carbon tetrachloride extinguishers were invented; however, since the fumes could be toxic, several people died from the use of these extinguishers in closed spaces. The next several decades saw improvements in extinguisher construction and chemical usage, allowing for more efficient and safe fire extinguishers, reports the IFSAC website.

Types of Fires

• Fire extinguishers are to be used for a specific type of fire. According to Australia's Fire Protection Association (FPA), Class A fires, started by combustibles such as paper and wood, use a Class A fire extinguisher. Class B fires start from flammable liquids like oil and gasoline, while Class C fires are sparked by live electricity. Class D fires start from combustible metals, usually found in factories and manufacturing plants. Cooking oils and fats used in commercial kitchens start Class K fires.

Considerations

• A, B and C extinguishers use a multi-purpose dry chemical, mono ammonium phosphate. If there is moisture present, this chemical is corrosive; however, it is a non-conducting chemical. To prevent corrosion, the FPA recommends cleaning and scrubbing the affected area immediately after the fire is out. This chemical is often used in schools and offices, as well as hospitals, businesses and some homes, says Fire-extinguisher101.com.

Types of Dry Chemicals

• The dry chemical sodium bicarbonate, a non-conducting material, is found in fire extinguishers for B and C fires. It is also non-toxic, reports Fire-extinguisher101.com, and non-corrosive. A sprayed area can be cleaned by vacuuming, sweeping or washing with water.

  Another dry chemical, known as Purple K, is potassium bicarbonate. Both non-conductive and non-corrosive, the spray from extinguishers with this material can be easily cleaned by sweeping, vacuuming or rinsing with water. It is only used for B and C extinguishers, says Fire-extinguisher.101.com, and is commonly found in military facilities and oil companies.

Other Components

• Water is often used in fire extinguishers, mixed with other components to extinguish the flame. Since the water can create a hazard for B and C fires, water is only used in Class A fires, reports Fire-extinguisher101.com. Carbon dioxide is also used in fire extinguishers, to eliminate oxygen from the flame, causing the fire to decrease and eventually stop. Since carbon dioxide leaves no residue or foam, it's most often used in theaters or rooms with expensive equipment.