HUMAN COMFORT In order to feel comfortable, humans must maintain an internal body temperature within a narrow range of 36.5-3rc. Metabolic processes that occur in the human body produce heat, and the body must lose this heat in order to maintain a stable internal temperature. Some processes are continuous (e.g. breathing, blood circulation, heart beat) and are called involuntary control mechanisms. Others such as muscular activity, clothing, posture and location are controlled and are called voluntary control mechanisms.