a chemical reaction obviously occurs, me and my friends make works bombs which you put toilet bowl cleaner containing the acid and tin foil in a bottle and gas is produced and it expands and blows up, the gas it produces is very milky and white and blows off pretty quickly, i have heard it is hydrogen gas and chlorine gas, which is it?? if someone were to be in an enclosed space with one of those going off and breathed that crap in would it harm them?? we want to be safe and just want to know what type of gas it is and what would happen if you were to inhale itYou should not be playing around with dangerous chemicals such as hydrochloric acid/aluminium - particularly enclosing these in a plastic bottle and causing explosions You should STOP doing this immediately before somebody gets seriously hurt , blinded possibly To answer your question: You are producing hydrogen gasNo chlorine gas is producedThe reaction equation is: 2 Al + 6 HCl 2 AlCl3 + 3 H2 The hydrogen gas is very explosive if in a confined spaceWhat you are doing is dangerous and not very cleverTake an interest in chemistry by all means , but do not play with danger You are unlikely to breathe in much of the hydrogen - it will rapidly rise away from you The danger comes from breathing in the HCl which will be sprayed about to form a mist after the explosion.Other related question