a man puts out a fire with an extinguisher
a man puts out a fire with an extinguisher

Fire Extinguishers Close Up

Parts and Contents

Firing Mechanism

All extinguishers have pins or pull tabs that have to be removed to activate the unit. plastic tie This feature prevents false activations. Some of our testers had difficulty removing the pin because it was held in by a thin sacrificial plastic tie.

We found most extinguishers had two levers that are squeezed together to activate. This is in contrast to the smaller 5-BC units designed for personal watercraft, which use a more simplified firing mechanism. Kidde uses a plunger mechanism and First Alert uses a trigger to activate their unit. Both are designed so that the firing mechanism does not extend past the width of the cylinder.

the nozzle of a fire extinguisher


There is a gauge on most extinguishers to measure the pressure of its contents. A fire gauges extinguisher can be "overcharged" meaning the contents are under too much pressure, "discharged" meaning that there is not enough pressure to work correctly or "in the green" which means that the unit is properly charged.

The standard round gauge was found on all but the personal watercraft units. Over time, or after it has been used, a fire extinguisher will loose pressure and will cease to work properly.

Most of our test extinguishers were not rechargeable. A rechargeable extinguisher can be taken to a service station for maintenance. If it is not rechargeable then it should be discarded when the gauge reads "discharged" or it has been in service for 12 years from manufacture.

Partial Discharge

Fire extinguishers are designed to rapidly release fire retardant onto their target. partial discharge when activated, the firing mechanism pierces a gas cylinder exerting additional pressure in the cylinder propelling the retardant out of the open nozzle. During our test we found that a partially discharged dry chemical extinguisher was inoperable after a few minutes. If you have a flare up after several minutes, a partially discharged unit might not work. It is important to replace or service the extinguisher as soon as possible.

Extinguisher Contents

Dry Chemical Extinguisher

The economically priced, handheld dry chemical fire extinguishers are the most common type found aboard recreational boats. The retardant functions by coating the material on fire and removing the oxygen from the flame similar to throwing a fire blanket on a fire. An accurate aim at the base of the fire directs the retardant at the source. Sometimes our testers found that by aiming at the top or middle of the fire, they could not put out the fire completely, and frequently required an additional extinguisher to finish the job. Clean up of dry chemical extinguishers can be messy and it is corrosive to electronic components and wiring.

Halon Replacement Extinguishers

Unlike dry chemical extinguishers, the Halotron extinguisher displaces oxygen from the fire. This gaseous fire suppressant allows for easy sight of the fire and does not harm engine or electronic components. Halon replacement extinguishers are ideal for separated, enclosed spaces such as an engine compartments for use through a Fire-Port. All portable halon replacement units are safe to breath but fixed systems using FE-241 are not. Drawbacks for these fire extinguishers are the higher price and bulkier size.