I know that we all know that things like petrol are not allowed in the cabin, but unfortunately there are still some passengers who aren't so sure of the rules. One of my friends was in the middle of boarding a flight when a passenger came on board and asked where he should put his camping stove. Nobody had picked up on it from check-in through to the gate staff and so it was left to the cabin crew to deal with the situation. As a result, I think it's always good to know what to do if somebody DOES bring dangerous goods on board when they aren't supposed to.