Duct smoke detectors, when installed in HVAC systems, automatically shut down the system fans upon detecting smoke. For HVAC systems with airflows exceeding 2,000 cfm, duct smoke detectors are required. This includes cases where multiple air-handling systems use common ducts with a combined design capacity greater than 2,000 cfm.
But when duct smoke detectors are required, where should they be located? Let’s look at the requirements in two of the prominent codes and standards.
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Building codes typically 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.” NFPA 90A: Standard for the Installation of Air-Conditioning and Ventilating Systems, paragraphs 4.3.7.3.1 and 4.3.8.3.1 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.”