An aqueous zinc nitrite solution which contains substantially no calcium ions is provided, in which, in terms of the aqueous zinc nitrite Zn2 solution having an NO2 concentration of 10% by weight, the sodium ion concentration is 200 to 2000 ppm and the sulfate ion concentration is 20 ppm or less in the solution. A group of dedicated test cells associated with one or more groups of regular OTP cells are used to test the support circuitry for the regular OTP cells. The first and second linear actuators may be connected to the pump in closed-loop manner, and each of the first and second linear actuators may have a first chamber and a second chamber separated by a piston. The scroll housing includes an air inlet for drawing air into the air filtration system and helmet, and at least one air outlet to distribute air flow to the air flow channel. A feedthrough subassembly is mounted within each of the receptacles, and a ferrule of each subassembly is coupled to the flange plate.