PORTABLE FIRE EXTINGUISHERS Purpose of Fire Extinguishers A portable fire extinguisher enables an individual with minimal training and orientation to extinguish an incipient fire without risk after calling the fire department. There have been many disastrous fires resulting from a delayed notification of the fire department while someone attempted extinguishment with portable fire extinguishers. One was the Beverly Hills Supper Club fire which claimed over 160 lives. Extinguisher Use Based on Fire Classification Fire extinguishers fall into four classes based on the type of fire(s) they are effective at extinguishing. Class A: Fires in ordinary combustibles such as wood, cloth, paper, rubber, and many plastics. They can be extinguished by cooling, smothering, and insulation, or by inhibiting the combustion chain reaction. Class B: Fires involving flammable or combustible liquids and gases, including greases and similar fuels. They can be extinguished by oxygen exclusion, smothering, and insulation, and by inhibiting the combustion chain reaction. Class C: Fires involving energized electrical equipment which requires the use of a nonconductive agent for protection of the extinguisher operator. If electrical power is eliminated, these fires become Class A or Class B, and may be extinguished accordingly. Class D: Fires in combustible metals such as magnesium, potassium, sodium, titanium, and zirconium. They require the use of an agent that absorbs heat and does not react with the burning metal. Class A and Class B fire extinguishers also have a numerical rating according to the size of the fire they potentially can extinguish. Although somewhat subjective, a 2-A extinguisher is roughly equivalent to a 2-1/2- gallon water extinguisher; a 4-A extinguisher has about as much extinguishing power as 5 gallons of water. FIRE PROTECTION SYSTEMS Class B extinguishers are given a numerical rating based on the area of flammable liquid they potentially can extinguish. As an estimate, it can be assumed that for each unit of "B, " one square foot of burning liquid can be extinguished. For example, a 10-B extinguisher can be used to extinguish a ten-square-foot liquid fire. It must be emphasized that the numerical rating is for estimating only, as the actual effectiveness will depend on such factors as user qualifications and skill. The classifications, including the numerical rating, can be compounded to provide multipurpose extinguishers. For example, a fire extinguisher listed as 4-A:20-B:C has the capacity of two 2-A extinguishers, 20 times the capacity of a single 1-B extinguisher, and it can be used on electrical (C) fires. To assist potential users, the NFPA has developed a color-graphic identification system for rapid identification of fires related to a particular extinguisher. This system is described in NFPA 10, Standard for Portable Fire Extinguishers.