The building codes do not prohibit floor registers in commercial buildings, however, the fire codes can restrict their usage. For example, NFPA 101: Life Safety Code, paragraph 9.2.1 states that “Air-conditioning, heating, ventilating ductwork, and related equipment shall be in accordance with NFPA 90A.” In NFPA 90A: Standard for the Installation of Air-Conditioning and Ventilating Systems, paragraphs 126.96.36.199.1 and 188.8.131.52.1 state that “Air inlets/outlets shall be located at least 3 inches above the floor, unless provisions have been made to prevent dirt and dust accumulations from entering the system.”
Commercial buildings typically have ceiling diffusers or sidewall grilles, but occasionally there is a need to locate air supplies or returns in the floor of a facility. Floor registers are common in residential applications. Before locating them in the floor a commercial building, a careful review of the applicable codes is imperative.