Abstract: An air supply and conditioning system 10 is provided having a constant speed air blower 26 whose output is controlled by a thermostatic throttle and check valve 28. The throttle and check valve provides a minimum air flow below a minimum ambient temperature, provides a maximum air flow above a maximum temperature, and provides a roughly linearly increasing flow from the minimum to the maximum ambient temperature. The air blower draws air through a pair of nuclear and biological contamination filters 22 from the ambient and impels the air through an air conditioning portion 14 and a pressurization door 42.