Petrol can overflow as a result of a flooded carburettor, and this means there's a danger of petrol leaking onto a hot engine or exhaust and potentially starting a fire or causing an explosion. To reduce this risk, carburettors (apart from the down draught type) must be fitted so that they allow any overflow to drain into a spirit-tight metal drip-tray.
The top of the tray has to be covered with a flame arresting mesh, made of copper or brass gauze, which is soldered to the rim of the tray. The tray must be removable or fitted with a fuel cock for emptying. A flame trap or air filter must be fitted to the air intake of petrol, petroil and paraffin engines. This will help to intercept flames produced as a result of an engine backfire. [2.19]