Artificial gas smell
The odour thought of as being the typical smell of gas – similar to a strong garlic odour – is in fact artificially added to the propane for safety reasons. The concentration at which it becomes detectable by smell is approximately 150 times lower than the concentration at which it becomes flammable. This means that, although the smell of gas should always be taken seriously, there is no cause for panic. If the smell of gas is detected, all sources of ignition (electrical switches, cigarette lighters, all types of engines) must be switched off or removed from the area of risk. The best way to make leaks visible is by applying soapy water: spray the gas pipes or hoses with soapy water and bubbles will appear where the leaks are.
Characteristics of PLG
Gaseous propane is heavier than air. Leaked gas will sink to ground level and seep downwards into lower-lying spaces or cavities. In closed spaces it may lie unnoticed for long periods, its smell being detectable only at ground or floor level, not at human head height. For this reason propane gas canisters should never be stored in closed rooms or near cellar windows or other underground spaces.
How to handle leaks
If there is a breach in the container, propane will leak out under pressure. For practical purposes, sealing the leak (e.g. with some form of sticker) is not possible. Leaks from the area where the propane is liquid (i.e. at the bottom) involve the loss of five times as much energy as leaks from the gaseous area. Leaking canisters should therefore be stood or laid such that the leak is now positioned in the upper section (i.e. where the propane is gaseous).
Behaviour of propane in pressurised containers
When gas is drawn off from the container, part of the liquid vaporises and in so doing becomes cooler. No air flows into the gas container. If a large quantity of gas is drawn off, the liquid cools to below 0°C and the container freezes. At or preferably before this point, the user should stop removing gas or reduce the flow. Attempting to carry on extracting gas will cause the pressure in the container to fall even further and the flow of gas will ultimately cease, even though liquid LPG is still present in the canister. In this state it will not flow out, even if the canister is left unsealed. However, if the canister subsequently warms up, the gas will begin to flow again unnoticed, a situation that can give rise to fires or explosions.