This page provides links to a number of compressed air and ambient air property calculators.
Dry Tank Technology. A robust and simple method of providing water-free compressed air.
The air compression process. Simple explanantion of what happen during the compression process.
In more detail. Equations and a more indepth explanation of the science.
Dew Point in Compressed Air – Frequently Asked Questions, Vaisala Application Note, 2013. http://www.vaisala.com/Vaisala%20Documents/Application%20notes/Dew-point-compressed-air-Application-note-B210991EN-B-LOW-v1.pdf
Humidity Conversion Formulas, Calculations formulas for Humidity, Vaisala 2013. http://www.vaisala.com/Vaisala%20Documents/Application%20notes/Humidity_Conversion_Formulas_B210973EN-F.pdf
Wagner, W. and Pruß, A., The IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use. Journal of Physical and Chemical Reference Data, June 2002, Vol. 31, Issue 2, pp387535 [pdf], http://thermophysics.ru/pdf_doc/IAPWS_1995.pdf [accessed 2017]