Air Properties

Air density is calculated with the CIPM 91 method. Open and free code.
Inputs to the calculation are pressure, temperature and relative humidity.
Output are Air density, Vapor pressure, Compressibility Factor, Viscosity and Speed of Sound
You find the algorithm details in this link
http://www.basicairdata.eu/air-properties.html
Main reference site
http://www.basicairdata.eu/android-air-properties.html

Free source online available

https://github.com/BasicAirData/AirProperties