6.3.2. Air Duct Systems

6.3.2. Air Duct Systems
6.3.2.1. Application
  1. This Subsection applies to the design, construction and installation of air duct distribution systems serving heating, ventilating and air-conditioning systems other than those in dwelling units covered by Part 9.
6.3.2.2. Drain Pans
  1. Dehumidifying cooling coil assemblies and condensate-producing heat exchangers shall be equipped with drain pans beneath them that are
    1. designed in accordance with Section 5.11, Drain Pans, of ANSI/ASHRAE 62.1, "Ventilation for Acceptable Indoor Air Quality,"
    2. provided with an outlet that is piped to the outside of the airstream in a location where condensate can be eliminated, and
    3. installed so that water drains freely from the pan.
6.3.2.3. Materials in Air Duct Systems
  1. All ducts, duct connectors, associated fittings and plenums used in air duct systems shall be constructed of materials as described in Article 3.6.5.1.
  2. Ducts that are used in a location where they may be subjected to excessive moisture shall have no appreciable loss of strength when wet and shall be resistant to moisture-induced corrosion.
  3. All ductwork and fittings shall be constructed and installed as recommended in SMACNA Manuals and ASHRAE Standards.
  4. All duct materials shall be suitable for exposure to the temperature and humidity of the air being carried and shall be resistant to corrosion caused by contaminants in the air being conveyed in the duct.
6.3.2.4. Connections in Air Duct Systems
  1. Air duct systems shall have tight-fitting connections throughout.
6.3.2.5. Duct Coverings and Linings
(See Note A-6.3.2.5.)
  1. Coverings, linings and associated adhesives and insulation used in air ducts, plenums and other parts of air duct systems shall comply with Article 3.6.5.4.
  2. Duct linings shall be installed so that they will not interfere with the operation of volume or balancing dampers or of fire dampers, fire stop flaps and other closures.
6.3.2.6. Clearance of Ducts and Plenums
  1. The clearance of ducts and plenums from combustible materials shall comply with Article 3.6.5.6.
6.3.2.7. Interconnection of Systems
  1. In a care or residential occupancy, air from one suite shall not be circulated to any other suite or to a public corridor.
  2. Except as permitted by Sentences (3) and 6.3.2.10.(6), air duct systems serving storage garages shall not be directly interconnected with other parts of the building.
  3. Exhaust ducts referred to in Sentence 6.3.2.10.(10) are permitted to exhaust through an enclosed storage garage prior to exhausting to the outdoors, provided
    1. the storage garage's exhaust system runs continuously,
    2. the capacity of the storage garage's exhaust system is equal to or exceeds the volume of the exhaust entering the garage, and
    3. a leakage rate 1 smoke/fire damper rated in accordance with CAN/ULC-S112.1, "Leakage Rated Dampers for Use in Smoke Control Systems," is provided near the duct outlet location in the storage garage to prevent air from the storage garage from entering the exhaust ductwork system in the event the building's exhaust fan is shut down.
6.3.2.8. Makeup Air
(See Note A-6.2.1.1.)
  1. In ventilating systems that exhaust air to the outdoors, provision shall be made for the admission of a supply of makeup air in sufficient quantity so that the operation of the exhaust system and other exhaust equipment or combustion equipment is not adversely affected.
  2. Makeup air facilities required by Sentence (1) shall be interlocked with the exhaust devices they serve so that both operate together.
  3. Where makeup air facilities are intended to introduce air directly from the outdoors to occupied parts of the building in winter, they shall incorporate means of tempering that air to maintain the indoor design temperature.
6.3.2.9. Supply, Return, Intake and Exhaust Air Openings
  1. Supply, return and exhaust air openings located less than 2 m above the floor in rooms or spaces in buildings shall be protected by grilles having openings of a size that will not allow the passage of a 15 mm diam sphere.
  2. Outdoor air intakes shall be located so that
    1. the quality of the air entering the building complies with Sentences 6.2.1.2.(2) and (3), and
    2. they are separated a minimum distance from sources of contaminants in accordance with Table 6.3.2.9.

      Table 6.3.2.9.
      Minimum Distances of Air Intakes from Sources of Contaminants
      Forming Part of Sentence 6.3.2.9.(2)

  3. Outdoor air intakes shall be installed not less than 0.3 m above roofs, landscape grades or other surfaces, taking into account anticipated snow accumulation levels.
  4. Exterior openings for outdoor air intakes and exhaust outlets shall be shielded from the entry of snow and rain and shall be fitted with corrosion-resistant screens of mesh having openings not larger than 15 mm, except where experience has shown that climatic conditions require larger openings to prevent the screen openings from icing over.
  5. Screens required in Sentence (4) shall be accessible for maintenance.
  6. Combustible grilles, diffusers and other devices covering supply, return, intake and exhaust openings shall comply with Article 3.6.5.7.
6.3.2.10. Exhaust Ducts and Outlets
  1. Except as provided in Sentence (2), exhaust ducts of non-mechanical ventilating systems serving separate rooms or spaces shall not be combined.
  2. Exhaust ducts of non-mechanical ventilating systems serving similar occupancies may be combined immediately below the point of final delivery to the outdoors, such as at the base of a roof ventilator.
  3. Exhaust ducts of ventilating systems shall have provision for the removal of condensation where this may be a problem.
  4. Exhaust outlets shall be designed to prevent backdraft under wind conditions.
  5. Except as permitted in Sentence (6), exhaust systems shall discharge directly to the outdoors.
    (See Note A-6.3.2.10.(5) and (6).)
  6. Exhaust systems are permitted to exhaust into a storage garage, provided
    1. they serve rooms that are accessible only from that storage garage,
    2. the exhaust contains no contaminants that would adversely affect the air quality in the storage garage (see Note A-6.3.2.10.(6)(b)), and
    3. they are designed in accordance with Sentence 6.3.2.7.(3). (See Note A-6.3.2.10.(5) and (6).)
  7. Exhaust ducts connected to laundry-drying equipment shall be
    1. independent of other exhaust ducts,
    2. accessible for inspection and cleaning, and
    3. constructed of a smooth corrosion-resistant material. (See Note A-6.3.2.10.(7) and (8).)
  8. Where collective venting of multiple installations of laundry-drying equipment is used, the ventilation system shall
    1. be connected to a common exhaust duct that is vented by one central exhaust fan and incorporates one central lint trap,
    2. include an interlock to activate the central exhaust fan when laundry-drying equipment is in use, and
    3. be provided with make-up air. (See Note A-6.3.2.10.(7) and (8).)
  9. Exhaust ducts or vents connected to laundry-drying equipment shall discharge directly to the outdoors.
  10. Except as provided in Sentence (12) and except for self-contained systems serving individual dwelling units, exhaust ducts serving rooms containing water closets, urinals, basins, showers or slop sinks shall be independent of other exhaust ducts.
  11. Except as provided in Sentence (12) and except for self-contained systems serving individual dwelling units, exhaust ducts serving rooms containing residential cooking equipment shall be independent of other exhaust ducts.
  12. Two or more exhaust systems described in Sentences (10) and (11) may be interconnected or connected with exhaust ducts serving other areas of the building, provided
    1. the connections are made at the inlet of an exhaust fan, and all interconnected systems are equipped with suitable back pressure devices to prevent the passage of odours from one system to another when the fan is not in operation, or
    2. the exhaust ducts discharge to a shaft that is served by an exhaust fan having a capacity that is equal to or greater than the combined capacity of the exhaust fans discharging to the plenum multiplied by the operation diversity factor, provided that the exhaust fan serving the shaft operates continuously (see Note A-6.3.2.10.(12)(b)).
  13. Where exhaust ducts containing air from conditioned spaces pass through or are adjacent to unconditioned spaces, the ducts shall be constructed to prevent condensation from forming on the inside or outside of the ducts.
6.3.2.11. Return-Air System
  1. Return-air systems shall comply with Article 3.6.5.8.
  2. Where a ceiling space is used as a return-air plenum, the requirements of Article 3.6.4.3. shall apply.
  3. A public corridor or exit shall not be used as a return-air plenum.
6.3.2.12. Underground Ducts
  1. Underground ducts shall
    1. be constructed and installed to provide interior drainage from and access to all low points,
    2. not be connected directly to a sewer, and
    3. be installed and constructed of materials recommended by ASHRAE and SMACNA Standards and HRAI Manuals.
  2. A clean-out or pump-out connection shall be provided in an underground duct system at every low point of the duct system.
6.3.2.13. Filters
  1. Air filters for air duct systems shall conform to the requirements for Class 2 air filter units as described in CAN/ULC-S111, "Fire Tests for Air Filter Units."
  2. When electrostatic-type filters are used, they shall be installed so as to ensure that the electric circuit is automatically de-energized when filter access doors are opened or, in dwelling units, when the furnace circulation fan is not operating.
6.3.2.14. Cleaning Devices
  1. Where outdoor air quality conditions do not meet the requirements of Sentence 6.2.1.2.(2), ventilation required by Sentence 6.3.1.1.(1) shall be provided by a ventilation system designed to include devices that reduce particles and gases to the maximum acceptable levels described in Sentence 6.2.1.2.(2) prior to the introduction of outdoor air to indoor occupied spaces.
  2. Where contaminants of concern are present in the outdoor air of the local area of the building site, ventilation required by Sentence 6.3.1.1.(1) shall be provided by a ventilation system designed to include devices that reduce the concentrations of contaminants to those permitted in the ACGIH's "Industrial Ventilation: A Manual of Recommended Practice for Design" prior to the introduction of outdoor air to indoor occupied spaces.
6.3.2.15. Evaporative Cooling Towers, Evaporative Fluid Coolers and Evaporative Condensers
  1. Discharge from evaporative cooling towers to ventilation air intakes shall comply with
    1. Sentence 6.3.2.9.(2), and
    2. CAN/CSA-Z317.2, "Special Requirements for Heating, Ventilation, and Air-Conditioning (HVAC) Systems in Health Care Facilities."
  2. The distance between the air intakes of evaporative cooling towers, evaporative fluid coolers and evaporative condensers in relation to kitchen exhaust outlets, vegetation or other sources of organic matter shall be not less than 4.6 m.
  3. Make-up water connections shall be equipped with backflow prevention devices that conform to Article 2.6.2.1. of Division B of the NPC.
  4. Water treatment equipment for biological growth control shall be provided in accordance with Sub-Section 7.6.2. of ASHRAE Guideline 12, "Minimizing the Risk of Legionellosis Associated with Building Water Systems."
  5. Drains, overflows and blow-downs shall be connected to the building's drainage system in accordance with Clause 2.4.2.1.(1)(e) of Division B of the NPC.
  6. Evaporative cooling towers, evaporative fluid coolers and evaporative condensers shall be provided with access ports, service platforms, fixed ladders and restraint connections to allow visual inspection, maintenance and testing.
6.3.2.16. Evaporative Air Coolers, Misters, Atomizers, Air Washers and Humidifiers
  1. The filter and water evaporation medium of every air washer and evaporative air cooler enclosed within a building shall be made of noncombustible material.
  2. Sumps for air washers and evaporative air coolers shall be constructed and installed so that they can be flushed and drained.
  3. Evaporative air coolers, misters, atomizers, air washers and humidifiers shall be designed in accordance with Sections 8 and 9 of ASHRAE Guideline 12, "Minimizing the Risk of Legionellosis Associated with Building Water Systems."
6.3.2.17. Fans and Associated Air-Handling Equipment
  1. Fans for heating, ventilating and air-conditioning systems shall be located and installed so that their operation
    1. does not adversely affect the draft required for proper operation of fuel-fired appliances, and
    2. does not allow the air in the duct system to be contaminated by air or gases from the boiler room or furnace room.
  2. Fans and associated air-handling equipment, such as air washers, filters and heating and cooling units, when installed on the roof or elsewhere outside the building, shall be of a type designed for outdoor use.
6.3.2.18. Vibration Isolation Connectors
  1. Vibration isolation connectors in air duct systems shall comply with Article 3.6.5.2.
6.3.2.19. Tape
  1. Tape used for sealing joints in air ducts, plenums and other parts of air duct systems shall comply with Article 3.6.5.3.

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