The dry Chemical powder is a multi-purpose fire extinguisher. Capacity: 4 kg. Discharge time 21.0 sec. The extinguisher will be rated for the size of the fire it can effectively extinguish. The rating is typically given in terms of the Class A, B, and C fire it can extinguish. The capacity of the extinguisher will determine how much fire retardant powder it can dispense. The capacity is usually given in pounds or kilograms. The operating pressure of the extinguisher will determine how far the fire retardant powder can be dispensed. The pressure is usually given in pounds per square inch (PSI) or bars. The discharge time of the extinguisher will determine how long the fire retardant powder can be dispensed. The discharge time is usually given in seconds. The height and weight of the extinguisher will determine how easily it can be handled and transported. The extinguishing agent used in an ABC Dry fireChemical Powder Fire Extinguisher is typically a dry chemical powder composed of monoammonium phosphate or sodium bicarbonate.