Air pressurized water

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Air pressurized water extinguishers or APW are types of fire extinguishers that extinguish burning material by absorbing heat . They contain 2.5 gallons of water or water with a wetting agent which is applied by means of a 1/2 inch hose with a smooth-bore nozzle attached to the tip. They produce a 40-50 foot stream of water, with a discharge time of about 45 seconds. Although only effective on only Class A fires, they have the advantage of being inexpensive, harmless, and easily refilled as well as having the advantage causing no mess, resulting in easy clean-up.

Also know as a water cans, they are commonly converted into makeshift CAFS extinguishers buy drilling two 1/8-1/16 inch holes in in the pickup tube. The unit is then filled with 1.5 gallons 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. CAFS extinguishers can also be fitted with air aspirators (commonly used on AFFF and FFFP foam extinguishers) which will result in a more expanded foam but will lack the 'staying power' or heat resistance of non-aspirated foam with does not break the bubbles.

[edit] Refilling

Water cans are easily refilled by filling the canister with water about 3/4 of the way up. The top is then screwed back on and the unit is pressurized with an air compressor.