Answer:
An increase in the intensity of sounds or fire issuing from a relief valve.
What does "contents under pressure" mean?
Propane serves as the propellant in all aerosols. R-12, a Freon that was the previous propellant, has been outlawed because it harms the ozone layer above the poles. Propane and R-12 share the same pressure-temperature characteristics.
Propane's boiling point is quite low. It desires a boil-off at ambient temperature. And it continues to do so until the pressure inside a closed container rises to roughly 150 psi (give or take depending on temperature), at which time the boiling point is raised high enough to cause the substance to stop boiling.
"Contents Under Pressure" is exactly what the notice indicates. Paint, hairspray, lubricant, wasp and hornet spray, among other liquids, can be found within an aerosol can, which is a pressure vessel. By inspecting the bottom, you may determine whether a vessel is a pressure vessel. If it is dished in like a bowl, it has the same pressure-holding end as a huge propane tank, with the exception that the curve on the latter has an outward orientation. On aerosol canisters, it is inward because they must sit upright for ease. A circular bottom just cannot accomplish that. But the top resembles an outer hemisphere more or less.
Thank you,
Eddie