system
Given the following post, respond as if you're commenting on Reddit:
human
Why do so many aerosol products use things like propane and butane as propellants? Why not air or nitrogen?

Title pretty much says it all. Why would they use something so flammable?  Is there some reason to not use compressed air?
gpt
Propane and butane are liquids when compressed. This allows a lot of the gas to be stored in a small space. Normal compressed air is still a gas, and has to be compressed at much higher pressures to even approach the compact storage of the usual propellants.