Aerosol inhaler for asthma is a pressurized aerosol which when used will eject the medicine as aerosol into the lungs.
The content inside asthma aerosol inhalers is propellant and the medicine. Typically the propellant is almost 99% of the content.
CFC propellants are replaced by HFA (hydrofluoroalkane) propellants as CFC is an ozone depleting substance. More information about HFA propellant inhalers can be found here.