The Physics
An encyclopedia of scientific essays

Pressure of a Fire Extinguisher

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Bibliographic Entry Result
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LeMay, Beall, Robblee, & Brower. Chemistry: Connections to our changing world. Prentice Hall, Upper Saddle River, NJ 07458, 1996. "The nitrogen gas inside a fire extinguisher is pressurized to 1345 kPa" 1345 kPa
Fire Extinguisher Safety Tips. Roswell Online 1997. "The pressure inside an extinguisher can be as high as 200 psi" 1379 kPa
Kidde Fire Fighting Extinguisher Product Guide [pdf]. 1997. [Table] 690–5861 kPa
Fire Extinguisher Maintenance. NIBCO OF COLORADO DIVISION, NIBCO, INC. OSHRC Docket No. 302 Occupational Safety and Health Review Commission, 10 June 1974. "The desired pressure in the cited dry chemical fire extinguisher is 175 psi, such a fire extinguisher not fully charged presents a hazard in the event of fir e … Respondent's maintenance man, Augustus Gearhart, refilled the cited fire extinguisher the night before the inspection as it had been used the prior day. When the same extinguisher was brought back to him after the inspection, the pressure gauge was in the low part of the white portion of the gauge. The gauge is calibrated at zero, 175, and 350 with the white portion of the gauge, being the acceptable range, taking [*30] up about 1/16 of the full dial, with 175 in the center of it." 1207–2413 kPa
Fireman from Engine 247 Brooklyn, Ny. Personal Interview. 22 May 2005. "100 psi" 690 kPa

Fire extinguishers generally come in 4 classes: A, B, C, and D. Each one can extinguish different types of fire:

  1. wood, cloth, paper, rubber, plastics
  2. flammable liquids such as gasoline or oil
  3. electrical equipment such as fuse boxes or circuit breakers
  4. combustible metal such as magnesium
  5. used in kitchens and environments where the probability of a grease fire is higher, this class was introduced in 1998.

There are four fire Extinguisher types, dry, halon, water, and carbon dioxide. A dry fire extinguisher is usually rated for multiple purpose use. They contain an extinguishing agent and use a compressed, non-flammable gas as a propellant. A halon fire extinguisher contains a gas that interrupts the chemical reaction that takes place when fuels burn. A water fire extinguisher contains water and compressed gas and should only be used on Class A fires. A carbon dioxide fire extinguisher will be most effective on Class B and C fires. Since the gas disperses quickly, this type of fire extinguisher is only effective from 3 to 8 feet. There is not one set pressure for all fire extinguishers, they vary by class. The ones they use in firehouses are 690 kPa but the pressure in carbon dioxide extinguishers can go up to 5861 kPa.

Victoria Poon -- 2005