Document jwna4epE1vm8R2254Z8rDm09

For CLASS A AND B FIRES--Wood, paper, etc, and oil, paint, and the like Operation When the extinguisher is inverted, the lead stopple covering the water and aluminum sulfate chamber drops and per mits the solution to mix with the water/sodium bicarbonate/foam stabilizer solution and produce foam The chemical reaction re leases COj gas with sufficient pressure to expel the foam For Class B fires in open containers, direct the stream against the back inside wall of the container--never discharge the foam stream di rectly into the burning liquid because it may cause the fire to spread out of the container On spill fires, stand back and gently arc the stream For Class A fires, aim the foam directly at the base of the flames Maintenance. Inspect periodically, discharge and recharge an nually Check for bent discharge elbow, corrosion, and other mechanical injury Thoroughly clean intenor, flush out hose and nozzle and clean outlet screen Mix chemicals in clean containers and strain into their respective chambers Caution Store in heated cabinet because an antifreeze solution cannot be used to protect from temperatures below 40 F, do not subject to temperatures above 120 F Fic 43-18 --Foam fire extinguisher (No longer manufactured, but replacement parts aie available ) cartndge that is lecommended bv the extmguishei manufactuiers Sodium bicaibonate-base dry chemical, the most common agent, is available in ordinary form and foam compatible form The foam compatible tvpe can be used simultaneously with foam without causing the foam blanket to break down Potassium bicaibonate-base div chemical, "purple K," is similat m extinguishing pioperties to sodium bicaibonate-base diy chemical, but it has twice the effective fiie-fighting ca pacity on a pound-to-pound basis This agent lias good moisture lepellencv and is compati ble with the simultaneous use of w.itei or foam Opeiator technique is not cntical be cause it does not allow fuel to reflash as easilv oi as lapidlv as sodium bicarbonate The absence of momentaiv flaie-up also permits the usei to approach flies moie closelv Also, the potassium compound extinguishes the leading edges of contained flammable liquid fires moie easily than the sodium compound This agent is also marketed as potassium bicarbonate/urea, and offers greater range Ammonium phosphate-base dry chemical (multipurpose) has operating characteristics on Class B and C files similar to sodium and potassium base dry chemical extinguishers When discharged into a Class A file, chemical leaction will destroy the flames and a coating, formed when the extinguishing agent softens and adheres to the burning surface thereby letaidmg fuithei combustion To obtain com plete extinguishment on Class A matenals, all burning areas must be thoioughlv exposed to the extinguishing agent Because any small burning ember may be a source of leigmbon, the impoitance of proper application on Class A flies is moie critical than with watei extinguisheis In the presence of moisture, multipurpose drv chemicals mav cause corlosion when discharged on metals It is there fore very important to clean up the multi purpose agent immediately aftei the fire is extinguished It is also important never to mix the ammonium phosphate-base agent with the potassium oi sodium bicarbonate-base 1353