One method of discharging pressure in the can

The 21/2-gallon pressurized water extinguisher (commonly called “the can”) is one of the best tools firefighters have for containing and extinguishing fires (see “The 21/2-Gallon Water Extinguisher,” by Harry Oster, Training Notebook, March 1999). However, after it has been used and needs recharging, many firefighters ignore some of the basic safety issues pertaining to the can.

Remember, any tool involving compressed air is extremely dangerous. All air pressure should be released prior to performing any maintenance or refilling the extinguisher. To release the pressure properly, invert the can (the neck should point to the ground, and the base should point up); this position enables all the pressure to be released. If the can has a carrying strap, place it over your shoulder to invert the can. Never attempt to place the handle of the can directly on the ground and force the body on it! This may damage the can’s components and put it out of service.

A firefighter should never straddle or lean over the can when recharging it with air pressure.

As you invert the can, grasp the discharge hose with your hand, or gently place one foot on the hose to secure it. This prevents the hose from whipping around and possibly striking you as you discharge the remaining air and water pressure. After discharging, check the pressure gauge to confirm that the can is depressurized. If the gauge indicates that pressure remains, invert the can again, and purge it. Never attempt to loosen the handle when the can is under pressure-the handle and stem may rapidly eject and result in injury. Only when you have released all the pressure can you remove the handle and stem from the top. Now you can perform any maintenance and refill the can with water.


When attaching the air hose, the firefighter can rotate the can or position his body to the side of the can so he can see the pressure gauge. Do not lean over the neck of the can while pressurizing it with air. (Photos by author.)

Once you inspect the can and determine it is duty ready, you can refill it with water and pressurize it with air. Some common mistakes often occur during this stage. A firefighter should never straddle the can when pressurizing it. If the handle is improperly threaded (cross-threaded) on the can or the threads are worn, the handle may disengage from the neck, fly up, and strike the firefighter. The firefighter should position his body to the side of the can with the pressure gauge in view.

The air hose now may be attached to pressurize the can. The can should only be pressurized to the proper pressure (normally 100 psi), which is usually the 12 o’clock position on the gauge. If, while pressurizing the can, you notice water and air to begin to emerge from the air fill valve stem, stop the air flow. The pressure inside the can has met or exceeded the pressure you are recharging it with and is expelling it through the valve stem. Check the pressure gauge to ensure the proper pressure has been reached. Remember, putting excessive pressure in the can could cause one of the can’s components to fail and possibly injure you.

After recharging the can with air pressure, invert it a couple of times, and recheck the pressure gauge. Listen carefully for air leaking out around the handle’s locking nut, the pressure gauge, and the valve stem. If the locking nut is leaking, try to hand-tighten it some more, which may stop the leak.

If that doesn’t work, discharge the can’s air pressure, tighten the locking nut, and repressurize the can. A minor leak at the valve stem or pressure gauge may sometimes be fixed by tightening the locking nuts with the proper size wrench. Preferably, do this when the can is depressurized. If any type of leak still persists after rechecking and recharging, take the can out of service and have it repaired.

Safety is not only a major factor on the fireground, it is also a primary concern in working with air pressure and the can. Remember, the can is only as good as the firefighter who knows its capabilities and limitations during extinguishment, maintenance, and recharging.

MICHAEL N. CIAMPO is a firefighter with the Fire Department of New York. He previously served with the District of Columbia Fire Department. He has a bachelor’s degree in fire science from John Jay College of Criminal Justice in New York City and was an instructor at the 1999 Fire Department Instructors Conference (FDIC) H.O.T program.

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