Water Fire Extinguishers
Water fire extinguishers are made for specific use, generally discharging a foamy liquid generally created to extinguish Class A fires such as organic solid material such as wood, Class B fires that involve liquid such as gas and oil, and Class C fires that involve electricity.
Wikipedia states, “Water cools burning material.”
“APW (Air pressurized water) cools burning material by absorbing heat from burning material. Effective on Class A fires, it has the advantage of being inexpensive, harmless, and relatively easy to clean up. In the United States, APW units contain 2.5 gallons (9 liters) of water in a tall, stainless steel cylinder. In Europe, they are typically mild steel lined with polyethylene, painted red, containing 6–9 liters (1.75–2.5 gallons) of water.
Water Mist uses a fine misting nozzle to break up a stream of deionized water to the point of not conducting electricity back to the operator. Class A and C rated. It is used widely in hospitals for the reason that, unlike other clean-agent suppressants, it is harmless and non-contaminant. These extinguishers come in 1.75 and 2.5 gallon units, painted white in the United States and red in Europe.
 Wet chemical and water additivesWet Chemical (potassium acetate, carbonate, or citrate) extinguishes the fire by forming a soapy foam blanket over the burning oil and by cooling the oil below its ignition temperature. Generally class A and K (F in Europe) only, although newer models are outfitted with misting nozzles as those used on water mist units to give these extinguishers class B and C firefighting capability.
Wetting Agents Detergent based additives used to break the surface tension of water and improve penetration of Class A fires.
Antifreeze Chemicals added to water to lower its freezing point to about −40 °F. Has no appreciable effect on extinguishing performance.”