| 3.6.5. |
Air Duct and Plenum Systems |
| 3.6.5.1. |
Duct Materials
- Except as permitted by Sentences (2) to (5) and Article 3.6.4.3., all ducts, duct connectors, associated fittings and plenums used in air duct systems shall be constructed of steel, aluminum alloy, copper, clay or other noncombustible material.
- Except as permitted by Sentence (3), ducts, associated fittings and plenums are permitted to contain combustible material provided they
- conform to the appropriate requirements for Class 1 duct materials in CAN/ULC-S110, "Test for Air Ducts,"
- conform to Article 3.1.5.18. in a building required to be of noncombustible construction,
- conform to Subsection 3.1.9.,
- are used only in horizontal runs in a building required to be of noncombustible construction,
- are not used in vertical runs serving more than 2 storeys in a building permitted to be of combustible construction, and
- are not used in air duct systems in which the air temperature could be more than 120°C.
- Combustible ducts which are part of a duct system conveying only ventilation air and are contained entirely within a dwelling unit need not comply with the requirements of Sentences (1) and (2).
- Duct sealants shall have a flame-spread rating not more than 25 and a smoke developed classification not more than 50.
- Duct connectors that contain combustible materials and that are used between ducts and air outlet units shall
- conform to the appropriate requirements for Class 1 air duct materials in CAN/ULC-S110, "Test for Air Ducts,"
- be not more than 4 m long,
- be used only in horizontal runs, and
- not penetrate a required fire separation.
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| 3.6.5.2. |
Vibration Isolation Connectors
- Except as permitted by Sentence (2), vibration isolation connectors in air duct systems shall be noncombustible.
- Combustible fabric vibration isolation connectors are permitted provided they
- are not more than 250 mm long,
- comply with the flame-resistance requirements of CAN/ULC-S109, "Flame Tests of Flame-Resistant Fabrics and Films," and
- are not used in a location where they are exposed to heated air or radiation from heat sources that could cause the exposed surface temperature to be more than 120°C.
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| 3.6.5.3. |
Tape
- Tape used to seal joints in air ducts, plenums and other parts of air duct systems shall meet the flame-resistance requirements for fabric in CAN/ULC-S109, "Flame Tests of Flame-Resistant Fabrics and Films."
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| 3.6.5.4. |
Coverings, Linings, Adhesives and Insulation
- Coverings, linings and associated adhesives and insulation for air ducts, plenums and other parts of air duct systems that would have an exposed surface temperature more than 120°C when exposed to heated air or radiation from heat sources shall be of noncombustible material.
- Except as permitted by Sentence (3), combustible coverings and linings, including associated adhesives and insulation, shall have
- a flame-spread rating not more than 25 on any exposed surface or any surface that would be exposed by cutting through the material in any direction, and
- a smoke developed classification not more than 50.
- The outer covering of ducts, plenums and other parts of air duct systems used within an assembly of combustible construction is permitted to have
- an exposed surface flame-spread rating not more than 75, and
- a smoke developed classification not more than 50.
- Combustible coverings and linings referred to in Sentences (2) and (3) shall not flame, glow, smoulder or smoke when tested in accordance with the method of test in ASTM C 411, "Hot-Surface Performance of High-Temperature Thermal Insulation," at the maximum temperature to which the coverings and linings are to be exposed in service.
- Except as permitted by Sentence (6), foamed plastic insulation shall not be used as part of an air duct system or for insulating an air duct.
- Foamed plastic insulation is permitted to be installed in a ceiling space that is used as a return air plenum provided the foamed plastic insulation is protected from exposure to the plenum in accordance with Article 3.1.5.14.
- Combustible coverings and linings of ducts, including associated adhesives and insulation, shall be interrupted where the duct penetrates a fire separation and at the immediate area of operation of heat sources in a duct system, including electric resistance heaters or fuel-burning heaters or furnaces.
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| 3.6.5.5. |
Insulation and Coverings
- Insulation and coverings on pipes in which the temperature of the fluid exceeds 120°C shall
- be made of noncombustible material, or
- not flame, glow, smoulder or smoke when tested in accordance with ASTM C 411, "Hot-Surface Performance of High-Temperature Thermal Insulation," at the maximum temperature to which the insulation or covering is to be exposed in service.
- Except as permitted by Sentence (5), where combustible insulation is used on piping in a horizontal service space or a vertical service space, the insulation and coverings on that piping shall have a flame-spread rating, on any exposed surface and on any surface that would be exposed by cutting through the material in any direction,
- not more than 25 in a building required to be of noncombustible construction, or
- not more than 75 in a building permitted to be of combustible construction.
- Except as permitted by Sentence (5), insulation and coverings on piping located in rooms and spaces other than the service spaces described in Sentence (2) shall have a flame-spread rating not more than that required for the interior finish of the ceiling of the room or space.
- Except as permitted by Sentence (5), combustible insulation and covering used on piping in a building within the scope of Subsection 3.2.6. shall have a smoke developed classification not more than 100.
- No flame-spread rating or smoke developed classification limits are required for combustible insulation and coverings used on piping located within a
- concealed space in a wall,
- floor slab, or
- noncombustible enclosure.
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| 3.6.5.6. |
Clearance of Ducts and Plenums
- The clearance of furnace plenums from combustible material shall conform to the requirements of the appropriate standards referenced in Sentence 6.2.1.5.(1).
- If the plenum clearance required in accordance with Sentence (1) is not more than 75 mm, the clearance between a supply duct and combustible material shall be not less than
- the required plenum clearance within a horizontal distance of 450 mm from the plenum, and
- 12 mm at a horizontal distance of 450 mm or more from the plenum, except that this clearance is permitted to be reduced to zero beyond a bend or offset in the duct sufficiently large to shield the remainder of the supply duct from direct radiation from the furnace heat exchanger. (See Note A-3.6.5.6.(2).)
- If the plenum clearance required in accordance with Sentence (1) is more than 75 mm but not more than 150 mm, the clearance between a supply duct and combustible material shall be not less than
- the required plenum clearance within a horizontal distance of 1 800 mm from the plenum, and
- 12 mm at a horizontal distance of 1 800 mm or more from the plenum, except that this distance is permitted to be reduced to zero beyond a bend or offset in the duct sufficiently large to shield the remainder of the supply duct from direct radiation from the furnace heat exchanger. (See Note A-3.6.5.6.(3).)
- If the plenum clearance required in accordance with Sentence (1) is more than 150 mm, the clearance between a supply duct and combustible material shall be not less than
- the required plenum clearance within a horizontal distance of 1 000 mm from the plenum,
- 150 mm within a horizontal distance between 1 000 mm and 1 800 mm from the plenum, and
- 25 mm at a horizontal distance of 1 800 mm or more from the plenum, except that this distance is permitted to be reduced to 8 mm beyond a bend or offset in the duct sufficiently large to shield the remainder of the supply duct from direct radiation from the furnace heat exchanger. (See Note A-3.6.5.6.(4).)
- If a register is installed in a floor directly over a pipeless furnace, a double-walled register box with not less than 100 mm between walls, or a register box with the warm-air passage completely surrounded by the cold-air passage, shall be permitted instead of the clearances listed in Sentences (2), (3) and (4).
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| 3.6.5.7. |
Supply, Return, Intake and Exhaust-Air Openings
- Combustible grilles, diffusers and other devices for supply, return, and exhaust-air openings in rooms shall conform to the flame-spread rating and smoke developed classification requirements for the interior finish of the surface on which they are installed.
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| 3.6.5.8. |
Return-Air System
- Except as required by Sentences (2) and (3), return ducts shall be constructed of material having a flame-spread rating not more than 150.
- If any part of a return duct will be exposed to radiation from the furnace heat exchanger or other radiating part within the furnace, that part of a return duct directly above or within 600mmof the outside furnace casing shall be noncombustible.
- Return ducts serving solid-fuel-burning furnaces shall be constructed of noncombustible material.
- Combustible return ducts shall be lined with noncombustible material
- below floor registers,
- at the bottom of vertical ducts, and
- under furnaces having a bottom return.
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