1.2 These requirements do not cover fan-coil units, central heating furnaces, panel or cable type radiant heating equipment, electric boilers, baseboard heaters, air heaters, nor any other electric heating equipment or appliances which are covered in or as a part of separate, individual requirements.
1.3 Duct heaters intended for use in a hazardous location are judged on the basis of its compliance with the requirements in this standard, together with the requirements for hazardous location equipment included in other applicable standards.
1.4 Duct heaters designed to be connected to air-duct systems are intended for installation in accordance with the Standard for Air Conditioning and Ventilating Systems, NFPA 90A, and the Standard for Warm Air Heating and Air Conditioning Systems, NFPA 90B.
1.5 These requirements apply to relays and other auxiliary control devices that may be provided as part of a duct heater to make it usable with other heating or cooling equipment, and are intended to take into account the effects of operating the duct heater in conjunction with or in proximity to such equipment. this standard.