Abstract: A system and method are provided for controlling temperature and humidity of an environment for a process chamber for semiconductor manufacturing materials. A supply of filtered, temperature and humidity controlled gaseous working fluid is provided to a process chamber, and is controlled by cascade control based upon sensing of environmental parameters to be controlled both upstream and downstream of a chemical filter, which can be a charcoal filter. A controller determines a first control error output by comparing a desired process parameter set point for the controlled environmental parameter of the gaseous working fluid with the first sensed value, determines a second set point from the first control error, and controls the supply of the temperature and humidity controlled gaseous working fluid based upon the second set point.