In general, the smell is a warning of potential danger. As soon as you smell gas, you should be very cautious. However, it is not the case that even the faintest whiff of gas indicates an imminent danger of fire. The threshold concentration for smelling LPG is roughly 150 times lower than the flammability threshold for LPG. In other words, if there is a faint smell of gas close up to the canister, this is no cause for concern. But if you can small gas at a distance of more than one metre from the canister, that is cause for alarm.