Posted By Steve Holliday
All aerosol cans are potentially hazardous due to their preasurised nature. The situation you describe, ie the dropping of the can, will have most likely caused a puncture of the can will have caused a rapid depressurisation which may have caused the can to rupture. Unlike the majority of aerosols WD40 is pressurised using carbon dioxide rather than LPG and therefore are inherently safer than their LPG pressurised counterparts. Assuming the cans are manufactured to the UK/US standards all the pressurised cans will be pressure tested at 55 degrees centigrade and in fact if the cans do fail they will initially fail by the domes, top first, popping out creating a larger volume can and thus reducing the pressure. In LPG pressurised cans the pressure would then equalised but hopefully the cause of the initial overpressure will be stabilised. It EXTREEMLY unlikely for cans to fail without mechanical damage!

To sum up, contents excluded, WD40 can are about as safe as aerosol cans get but will still cause hazards if punctured.

As a useless fact of the day, in the aerosol industry cans that contain LPG only are internally referred to as BOMBS!

Posted By Frank Hallett
Wai, We're in danger of making assumptions here about the explosion and the initiating event 'cos it hasn't been questioned yet even though the details are very sketchy.

The full circumstances of the event reported by you are essential to assisting you to determine the true cause and to minimise a recurrence.

The potential for a WD40 can to actually explode in normal use [including being dropped] is extremely low, although always possible. These containers are used in their thousands every day in a huge range of environments with effectively no meaningful reported explosion data.

Frank Hallett