Fire Extinguisher

Overview

A portable fire extinguisher is a self-contained pressure vessel that stores a chemical agent and expels it onto a fire under stored gas pressure. This unit is a stored-pressure ABC dry-chemical type: a steel cylinder is charged with mono-ammonium phosphate powder and pressurized with dry nitrogen, so squeezing the valve lever immediately drives agent out through the discharge horn. The ABC rating means it is effective on Class A (ordinary combustibles), Class B (flammable liquids) and Class C (energized electrical) fires, the most common hazards in homes, vehicles and commercial occupancies.

The pressure boundary is the welded Cylinder, which holds both the powder charge and the nitrogen expellant. Pressure is held back by the Valve Assembly, a brass body whose spring-loaded stem seals against a seat until lifted. The operator interacts with the Handle / Lever Assembly, a fixed carry handle and pivoting lever locked by a pull pin and tamper seal. When discharged, agent leaves through the Discharge Assembly hose and horn, which shape the powder into a directed cone. The Mounting Bracket holds the unit at ready height and the Instruction Plate carries the UL rating and service record.

How it works

In storage the cylinder sits pressurized to roughly 195 psi, with the gauge needle in the green band confirming the charge. To operate, the user pulls the safety pin, breaking the tamper seal, then aims the horn at the base of the fire and squeezes the lever. Squeezing rotates the lever about its pivot and depresses the valve stem off its seat. Nitrogen pressure forces powder up the internal siphon tube, through the valve and hose, and out the horn. The mono-ammonium phosphate interrupts the chemical chain reaction of combustion and melts to form a barrier that smothers Class A embers. Sweeping the discharge side to side coats the burning surface until the agent is exhausted, typically within about twenty seconds.