NFPA 99 addresses medical gas systems, electrical systems, fire safety, and emergency operations in health care facilities. Medical gas piping delivers oxygen, nitrogen, and other gases to patient care areas. Redundant supply ensures continuous gas availability. Electrical systems must be highly reliable with generator backup. Emergency lighting and circuits must maintain functionality during power loss. Hospitals typically have three levels of electrical service: normal, critical branch (for essential systems), and equipment system. Alarm systems must alert staff immediately to equipment failures.