Lead-Acid (LA) and Nickel Cadmium (NiCd) vent hydrogen and oxygen when they are being charged. In the case of Valve-Regulated designs, the The above question is frequently asked and often the answer is what seems to be the standard answer to every stationary battery question – it depends! Well, the purpose of this technical note is to give an honest answer, taking into consideration years of experience and perusal of many codes, standards, guides and practices. Some of these are enforceable by law and others are just plain common sense. Many of these requirements are referenced below and advice is given.