Dry powder fire extinguishing agents are usually stored in dry powder fire extinguishers or dry powder fire extinguishing equipment. When extinguishing a fire, the dry powder is ejected from the nozzle by the pressure of the pressurized gas carbon dioxide or nitrogen, forming a mist-like powder flow sandwiching the pressurized gas, and shoots toward the burning material. The principle of a series of physical and chemical reactions occurring when the dry powder contacts with the flame is as follows: the sodium bicarbonate in the dry powder is decomposed by high temperature. The reaction is an endothermic reaction. The reaction releases a large amount of carbon dioxide and water. The water becomes water vapor when heated and absorbs a large amount of heat. Play the role of cooling and diluting combustible gas; after the dry powder enters the flame, due to the absorption and scattering of the dry powder, it reduces the heat radiation of the flame to the fuel and reduces the evaporation rate of the liquid.
Dry powder fire extinguishing agent cannot be combined with protein foam and general foam. Because dry powder has a greater destructive effect on protein foam and general synthetic foam. For some highly diffusible gases such as hydrogen, acetylene gas, and dry powder, it is difficult to dilute the entire space after spraying. For precision instruments and meters, residues will be left, and dry powder is not applicable.
When the dry powder fire extinguisher is in operation, the dry powder fire extinguishing agent should be kept upright and spray the dry powder jet to the root of the burning flame. When using outdoors, pay attention to standing upwind to spray, and as the range shortens, gradually approach the combustion zone to increase the efficiency of fire fighting. When extinguishing a fire, it should be close to flame spraying; the dry powder spraying time is short, and the fire extinguishing agent should be selected before spraying. Because the dry powder is easy to disperse, it is not suitable to spray against the wind. When extinguishing oil fires on the ground, take a flat shooting position, swing the hose from side to side, and advance quickly from far to near.
Dry powder extinguishing agent can suppress the chain reaction of combustion and extinguish the fire. It is suitable for extinguishing liquid, gas, and electrical fires (dry powder has electrical insulation performance of more than 50,000 volts). Some can also put out solid fires. Dry powder fire extinguishers cannot extinguish light metal fires. When using, first pull out the safety pin (some pull up the ring), and then press the handle, the dry powder can be sprayed. When extinguishing the fire, it should be close to the flame jet; the dry powder jet time is short, and the jet target must be selected before jetting. Because the dry powder is easy to disperse, it is not suitable to spray against the wind. Pay attention to maintaining the fire extinguisher and place it in a well-accessible, dry and ventilated place.
The manufacturer stated that it is necessary to check whether the dry powder is agglomerated twice a year, and if there is a block, replace it in time; check the weight of the agent once a year, if it is less than the specified weight or look at the pressure gauge, the air pressure should be filled in time.