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 SoundYou find the algorithm details in this link http://www.basicairdata.eu/air-properties.htmlMain reference site http://www.basicairdata.eu/android-air-properties.htmlFree source online availablehttps://github.com/BasicAirData/AirProperties