FIRE EXTINGUISHER
Fire extinguisher, portable or movable apparatus used to put out a small fire by directing onto it a substance that cools the burning material, deprives the flame of oxygen, or interferes with the chemical reactions occurring in the flame. Water performs two of these functions: its conversion to steam absorbs heat, and the steam displaces the air from the vicinity of the flame. Many simple fire extinguishers, therefore, are small tanks equipped with hand pumps or sources of compressed gas to propel water through a nozzle. The water may contain a wetting agent to make it more effective against fires in upholstery, an additive to produce a stable foam that acts as a barrier against oxygen, or an antifreeze. Carbon dioxide is a common propellant, brought into play by removing the locking pin of the cylinder valve containing the liquefied gas; this method has superseded the process, used in the soda-acid fire extinguisher, of generating carbon dioxide by mixing sulfuric acid with a solution of sodium bicarbonate.
Classes of Fires
There are four classes of fires:
Class A: Ordinary solid combustibles such as paper, wood, cloth and some plastics.
Class B: Flammable liquids such as alcohol, ether, oil, gasoline and grease, which are best extinguished by smothering.
Class C: Electrical equipment, appliances and wiring in which the use or a nonconductive extinguishing agent prevents injury from electrical shock. Don’t use water.
Class D: Certain flammable metallic substances such as sodium and potassium. These materials are normally not found in the Medical Center.
Types of Fire Extinguishers
Type A: Pressurized water to be used on Class A fire only. Do not use on Class B or C fires; may cause fire spread or electrical shock.
Type ABC: Dry chemical effective on all classes of fires
Type BC: Carbon dioxide to be used on chemical or electrical fires
Type K: Used in kitchens on grease fires
PASS
To use a fire extinguisher, follow the acronym PASS
Pull – Pull the pin on the extinguisher
Aim – Aim the nozzle at the base of the fire
Squeeze – Squeeze the trigger to release the product
Sweep – Sweep the nozzle from side to side (slowly)