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.