the contents of a can of air freshener are gaseous when sprayed but remain a liquid in the can due to what?

Answer 1

Pressure.
When you reduce the pressure over a liquid surface to below vapor pressure, it boils off. If you increase the pressure, it does not boil until a higher temperature (eg - pressure cooker). The pressure is high enough in the can to hold the contents in a liquid state, but when you reduce the pressure by opening a valve, it vaporizes.