Fire Extinguishers - First Line Defense-Environmental Health & Safety - Carnegie Mellon University

Monday, April 15, 2013

Fire Extinguishers - First Line Defense

You’re walking through the corridor of the building you work in and come upon a trash can on fire. Since you work in this building almost every day you know exactly where the nearest fire extinguisher is located, right? You follow the P.A.S.S. procedure to properly operate the fire extinguisher and extinguish the fire. Do you know what the acronym P.A.S.S. means? If not consider signing up for a fire extinguisher training class on our web-site at

This fire extinguisher functioned properly because it was inspected, tested and maintained per NFPA 10, The Standard for Portable Fire Extinguishers. Maintenance is required to include a thorough examination of the mechanical parts, extinguishing agents, and expelling means of each extinguisher. 

All types of fire extinguishers should be inspected, tested and maintained annually. The extinguisher is checked to make sure it has proper pressure, the correct volume of extinguishing agent by weighing it, the extinguisher is within the required hydrostatic test date, and all internal and external parts are serviceable.

Often dry chemical and dry powder types of fire extinguishers are struck on the bottom with a rubber mallet. This is called “fluffing” the extinguishing agent to make certain it is free flowing. The extinguisher will then receive a new tamper seal secured around the safety pin and a yearly service tag installed.

OSHA requires hydrostatic testing in accordance to the schedule listed in 29CFR 1910.157. This occurs every 5 years for most fire extinguishers.

The fire extinguisher is emptied, depressurized and the valve is removed. The pressure vessel (extinguisher) is filled with water, placed inside a safety cage and pressurized to the specific test pressure for a specific time period. If no failures are detected the fire extinguisher passes. It is than emptied of water, dried thoroughly and re-charged and ready for service.

By: Richard Caruso,, 412-268-9404