Established in 1991, National HVAC Service, Ltd. is a provider of heating, air conditioning and mechanical services in the commercial, industrial and institutional markets. Located in Little Rock, Ark., the company specializes in preventive maintenance programs as well as computerized maintenance tasking. It also specializes in mechanical system installations, system design-build, building control systems, sheet metal ductwork, process water/air piping and chiller overhauls/rebuilds, to name a few. Through its computerized management program, National HVAC Service, Ltd. monitors and tracks refrigerant usage.