Environmental control apparatus, namely equipment for simulating varying altitude conditions by controlling environmental conditions within a closed environment, including oxygen content and humidity; Components for environmental control apparatus, namely masks for providing a breathable gas to a user, the gas having at least a controlled oxygen content; Components for environmental control apparatus, namely pulse oximeters for providing data to control systems for controlling the environment in a closed system based on established parameters; Components for environmental control apparatus, namely oxygen monitors for monitoring the oxygen content in an environmentally controlled closed environment; Components for environmental control apparatus, namely Humidity Controls; Components for environmental control apparatus, namely control systems for controlling environmental factors within a closed environment, including oxygen content, carbon dioxide content, nitrogen content, and humidity; HVAC units; Environmental control apparatus, namely enclosures for enclosing a controlled environment having a variable oxygen content