There are two problems you are discussing.
The sealed pressurised canister rupturing due to the build-up of internal pressure causing a mechanical explosion.
And the flammability of the contents.
Notwithstanding what you are applying; be it perfume, (as to under arms etc.) or a sticky substance designed to hold things in place (as in hair spray), or paint, or glue, or gap filling foam; to name a few, the propellant these days is a hydrocarbon…. Liquefied Petroleum Gas (LPG), usually n-butane or iso-butane. Although industrial aerosols intended to be used out doors or in cold environments may use propane. These are flammable by themselves let alone the contents.
The common received wisdom is that LPG being heavier than air (relative density) will sink. However, don’t forget this LPG is vaporised into a fine mist and efficiently mixed with air entrained into the gas stream by Bernoulli's principle and venturi action. The gas can further be heated or caught into up-draughts or thermals, such as in front of fires heaters of hair dryers.
