Use Environment per MIL HDBK-217 (Ground):
Ground, Benign: Non-mobile, temperature and humidity controlled environments readily accessible to maintenance; includes laboratory instruments and test equipment, medical electronic equipment, business and scientific computer complexes, and missiles and support equipment in ground silos. This would include any office or lab environment in which people are permanently stationed.
Ground, Fixed: Moderately controlled environments such as installation in permanent racks with adequate cooling air and possible installation in unheated buildings; includes permanent installation of air traffic control radar and communications facilities. The term cooling air does not mean air conditioning, as cooling air could be any movement of air over the equipment that is at or below the temperature of the equipment. In other words, air used to draw heat away from the equipment, which would then either cool the gear down or stabilize the temperature to that of the air temperature.
Ground, Mobile: Equipment installed on wheeled or tracked vehicles and equipment manually transported; includes tactical missile ground support equipment, mobile communication equipment, tactical fire direction systems, handheld communications equipment, laser designations and range finders. Mobile implies the equipment will encounter vibration.