Model MDG nitrogen filler (referred to as filler hereinafter) can be used for filling nitrogen to cylinders to be pressurized by nitrogen in the manufacturers of fire fighting equipment. For instance, after the cylinder is filled with dry powder, inactive gas-nitrogen has to be filled for pressurization. When the dry powder cylinder is used for putting out a fire, the dry powder will be sprayed quickly to the flame together with the pressurized nitrogen to extinguish the fire promptly.