|All aerosol cans carry a safety warning about not exposing them to sunlight or throwing them onto a fire. Lets see why. |
There are volatile liquids inside often a LPG propellant. If these are heated, then they will produce more vapour inside the can, which will make the pressure rise very quickly. A temperature rise of 30 °C can double the pressure inside. Even though the cans are tested, they will burst if the pressure goes up too far. A bursting can could be dangerous in its own right.
However, as well as being volatile, the propellant or other contents could also be flammable.
Even if the liquefied gas propellant has run out (i.e. the can is empty) or it uses a pressurised gas propellant, the can should still not be heated. This is because of the effect of the pressure law (see page 14). Raising the temperature of the gas inside will increase its pressure and, once again, the can might burst.