{"data":{"id":"us-nyc/n.y.c.-admin.-code-mc-602","jurisdiction":"us-nyc","citation":"N.Y.C. Admin. Code § MC 602","heading":"Section MC 602: Plenums","body":"602.1 General.\n\nSupply, return, exhaust, relief and ventilation air plenums shall be limited to uninhabited crawl spaces, areas above a finished ceiling or below the finished floor, attic spaces and mechanical equipment rooms. Plenums shall be limited to one fire area. Air systems shall be fully ducted from the boundary of the fire area served to the air-handling equipment or associated mechanical room serving as a return air plenum. Fuel-fired appliances shall not be installed within a plenum.\n\nException: In a fully sprinklered building, return air plenums may be separated by combination fire smoke dampers and a fully ducted return is not required. The requirements of Section 601.2.1 shall apply.\n\n602.2 Construction.\n\nPlenum enclosure construction materials that are exposed to the airflow shall comply with the requirements of Section 703.5 of the New York City Building Code or such materials shall have a flame spread index of not more than 25 and a smoke-developed index of not more than 50 when tested in accordance with ASTM E 84 or UL 723. The temperature of air delivered to or through these plenums shall not exceed 250°F (121.1°C), except where used as part of an engineered smoke control system.\n\nThe use of gypsum boards to form plenums shall be limited to systems where the air temperatures do not exceed 125°F (51.7°C) and the building and mechanical system design conditions are such that the gypsum board surface temperature will be maintained above the airstream dew-point temperature. Air plenums formed by gypsum boards shall not be incorporated in air-handling systems utilizing evaporative coolers.\n\n602.2.1 Materials within plenums.\n\nExcept as required by Sections 602.2.1.1 through 602.2.1.7, materials within plenums shall be noncombustible or shall be listed and labeled as having a flame spread index of not more than 25 and a smoke-developed index of not more than 50 when tested in accordance with ASTM E 84 or UL 723.\n\nExceptions:\n\n1. Rigid and flexible ducts and connectors shall conform to Section 603.\n\n2. Duct coverings, linings, tape and connectors shall conform to Sections 603 and 604.\n\n3. This section shall not apply to materials exposed within plenums in one- and two-family dwellings.\n\n4. This section shall not apply to smoke detectors.\n\n5. Combustible materials fully enclosed within one of the following:\n\n5.1. Continuous noncombustible raceways or enclosures.\n\n5.2. Approved gypsum board assemblies.\n\n5.3. Materials listed and labeled for installation within a plenum.\n\n6. Materials in Group H-5 fabrication areas and the areas above and below the fabrication area that share a common air recirculation path with the fabrication area.\n\n602.2.1.1 Wiring.\n\nCombustible electrical wires and cables and optical fiber cables exposed within a plenum shall be listed as having a maximum peak optical density of 0.50 or less, an average optical density of 0.15 or less, and a maximum flame spread distance of 5 feet (1524 mm) or less when tested in accordance with NFPA 262 or shall be installed in metal raceways or metal sheathed cable. Combustible optical fiber and communication raceways exposed within a plenum shall be listed as having a maximum peak optical density of 0.5 or less, an average optical density of 0.15 or less, and a maximum flame spread distance of 5 feet (1524 mm) or less when tested in accordance with UL 2024. Only plenum-rated wires and cables shall be installed in plenum-rated raceways. Electrical wires and cables, optical fiber cables and raceways addressed in this section shall be listed and labeled and shall be installed in accordance with New York City Electrical Code.\n\n602.2.1.2 Fire sprinkler piping.\n\nPlastic fire sprinkler piping exposed within a plenum shall be used only in wet pipe systems and shall have a peak optical density of 0.50 or less, an average optical density of 0.15 or less, and a flame spread of 5 feet (1524 mm) or less when tested in accordance with UL 1887. Piping shall be listed and labeled.\n\n602.2.1.3 Pneumatic tubing.\n\nCombustible pneumatic tubing exposed within a plenum shall have a peak optical density of 0.50 or less, an average optical density of 0.15 or less, and a flame spread of 5 feet (1524 mm) or less when tested in accordance with UL 1820. Combustible pneumatic tubing shall be listed and labeled.\n\n602.2.1.4 Electrical equipment in plenums.\n\nElectrical equipment exposed within a plenum shall comply with Sections 602.2.1.4.1 and 602.2.1.4.2.\n\n602.2.1.4.1 Equipment in metallic enclosures.\n\nElectrical equipment with metallic enclosures exposed within a plenum shall be permitted.\n\n602.2.1.4.2 Equipment in combustible enclosures.\n\nElectrical equipment with combustible enclosures exposed within a plenum shall be listed and labeled for such use in accordance with UL 2043.\n\n602.2.1.5 Discrete plumbing and mechanical products in plenums.\n\nWhere discrete plumbing and mechanical products and appurtenances are located in a plenum and have exposed combustible material, they shall be listed and labeled for such use in accordance with UL 2043.\n\n602.2.1.6 Foam plastic insulation.\n\nFoam plastic insulation used in plenums as interior wall or ceiling finish or as interior trim shall exhibit a flame spread index of 75 or less and a smoke-developed index of 450 or less when tested in accordance with ASTM E 84 or UL 723 and shall also comply with one or more of Sections 602.2.1.6.1, 602.2.1.6.2 and 602.2.1.6.3.\n\n602.2.1.6.1 Separation required.\n\nThe foam plastic insulation shall be separated from the plenum by a thermal barrier complying with Section 2603.4 of the New York City Building Code and shall exhibit a flame spread index of 75 or less and a smoke-developed index of 450 or less when tested in accordance with ASTM E 84 or UL 723 at the thickness and density intended for use.\n\n602.2.1.6.2 Approval.\n\nThe foam plastic insulation shall exhibit a flame spread index of 25 or less and a smoke-developed index of 50 or less when tested in accordance with ASTM E 84 or UL 723 at the thickness and density intended for use and shall meet the acceptance criteria of Section 803.1.2 of the New York City Building Code when tested in accordance with NFPA 286.\n\nThe foam plastic insulation shall be approved based on tests conducted in accordance with Section 2603.9 of the New York City Building Code.\n\n602.2.1.6.3 Covering.\n\nThe foam plastic insulation shall be covered by corrosion-resistant steel having a base metal thickness of not less than 0.0160 inch (0.4 mm) and shall exhibit a flame spread index of 75 or less and a smoke-developed index of 450 or less when tested in accordance with ASTM E 84 or UL 723 at the thickness and density intended for use.\n\n602.2.1.7 Plastic pipe and tube.\n\nPlastic piping and tubing shall be listed and shall exhibit a flame spread index of not more than 25 and a smoke-developed index of not more than 50 when tested in accordance with ASTM E 84 or UL 723.\n\n602.3 Stud cavity and joist space plenums.\n\nStud wall cavities and the spaces between solid floor joists to be utilized as air plenums shall comply with the following conditions:\n\n1. Such cavities or spaces shall not be utilized as a plenum for supply air.\n\n2. Such cavities or spaces shall not be part of a required fire-resistance-rated assembly.\n\n3. Stud wall cavities shall not convey air from more than one floor level.\n\n4. Stud wall cavities and joist space plenums shall comply with the floor penetration protection requirements of the New York City Building Code.\n\n5. Stud wall cavities and joist space plenums shall be isolated from adjacent concealed spaces by approved fireblocking as required in the New York City Building Code.\n\n6. Stud wall cavities in the outside walls of building envelope assemblies shall not be utilized as air plenums.\n\n602.4 Flood hazard.\n\nFor structures located in flood hazard areas, plenum spaces shall comply with the additional requirements of Appendix G of the New York City Building Code.\n\n602.5 Firestopping.\n\nWhere required by the New York City Building Code, through penetrations shall be firestopped in accordance with Section 714 of the New York City Building Code.\n\n602.6 Periodic inspections to prevent contamination of mechanical systems.\n\nCovered buildings, as described in Section 28-325.1 of the New York City Administrative Code, shall be subject to periodic inspections to prevent contamination of mechanical systems in accordance with Section 28-325.2 of the New York City Administrative Code.","path":["New York City Administrative Code","Title 28","Chapter 8: New York City Mechanical Code"],"source_url":"https://files.amlegal.com/pdffiles/NewYorkCity/Admin/XML.zip","current_through":"Local Law 2026/135 (enacted August 31, 2026)","vintage":"","retrieved_at":"2026-09-06T02:48:57Z","sha256":"ca2fdd041a193c15c5ba081f7349bc9a62b10d843c93fc9f2988a0ec9dc557c4","source_id":"us-nyc","stale":false,"prev":"us-nyc/n.y.c.-admin.-code-mc-601","next":"us-nyc/n.y.c.-admin.-code-mc-603"},"notice":"GroundRules: Original legal text. Not legal advice."}