Background: You state that as a Senior Mechanical Engineer for HVAC systems in Air Force facilities, you are responsible for setting design standards for mechanical systems in the facilities (primarily office buildings but also childcare, emergency operations, & dormitory-type buildings). In this capacity, you sometimes use HVAC systems that may expose facility occupants to the system’s refrigerant (as would happen if a refrigerant line inside the facility would rupture or become disconnected). Therefore, you limit the amount of refrigerant for a system to protect occupants in the event of an accidental release of refrigerant from these systems by following the safety guidelines published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). You state that the Air Force relies on the ASHRAE standard 15/34-2002 (Safety Standard for Refrigeration Systems and Designation and Safety Classification of Refrigerants) definition of oxygen deficient environment of 18% oxygen (which is equivalent to 140,000 ppm or 14% concentration of refrigerant).