Air pressurized water or APW extinguishers are types of fire extinguishers that extinguish burning material by absorbing heat. They contain 2.5 gallons (9.5 l) of water or water with a wetting agent which is applied by means of a ½-inch hose

Hose (tubing)

A hose is a hollow tube designed to carry fluids from one location to another. Hoses are also sometimes called pipes , or more generally tubing...

 with a smooth-bore nozzle

Nozzle

A nozzle is a device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....

 attached to the tip. They will initially produce a 40–50 foot stream of water, with a discharge time of about 50 seconds. Although only effective on only Class A fires, they have the advantage of being inexpensive to operate and causing minimal damage and clean-up.

Also known as a water cans, they are commonly converted into makeshift CAFS

Compressed Air Foam System

A compressed air foam system is a system used in firefighting to deliver fire retardant foam for the purpose of extinguishing a fire or protecting unburned areas from becoming involved in flame.-Description:...

 extinguishers by drilling two 1/8–1/16 inch holes in the pickup tube. The unit is then filled with 1.5 gallons (5.7 l) of water and Class A foam, AFFF, FFFP or commercial detergent is added to the water in a 1% ratio for class A fires and a 3–6% ratio for Class B fires. Typically, the tip of the smooth-bore application nozzle is then cut off to allow the foam to properly expand. Keeping the nozzle will result in wetter foam and longer range. Cutting the nozzle will result in an expanded, dry foam but will lack the range of the standard water nozzle. Water extinguishers can also be fitted with air aspirators when used with foam (commonly used on AFFF and FFFP foam extinguishers) which will result in a more expanded foam but will lack the durability or heat resistance of compressed air foam.

Refilling

Water cans are easily refilled by filling the cylinder with water about three-quarters of the way up. The top is then screwed back on and the unit is pressurized with an air compressor

Air compressor

An air compressor is a device that converts power into kinetic energy by compressing and pressurizing air, which, on command, can be released in quick bursts...

 via the Schrader valve

Schrader valve

The Schrader valve is a brand of pneumatic tire valve used on virtually every motor vehicle in the world today. The Schrader company, for which it was named, was founded in 1844 by August Schrader...

located on the back of the valve body.