Ducts, piping, refrigeration and venting (9.33.6 to 9.33.10) (HVAC

Last updated October 22, 2026

Values this chapter turns on

unfinished basement area per warm-air supply outlet: 40 m²; unfinished basement area per warm-air supply outlet
max exposed radiator surface temperature: 70°C; max exposed radiator surface temperature
max exposed surface temperature of insulated pipe: 52°C; max exposed surface temperature of insulated pipe
insulation on ducts exposed to unheated space: RSI 2.1; insulation on ducts exposed to unheated space

Subsections 9.33.6. to 9.33.10. are the most number-dense part of the heating rules: duct materials, metal thickness, plenum clearances, supply outlet spacing, return air, pipe clearances, cooling coil placement and venting. Expect many direct lookups here, plus a few scenario questions on clearances.

Air duct systems

Scope OBC Div. B 9.33.6.1.. This Subsection covers duct systems serving one dwelling unit within Part 9. A system with rated heat input over 120 kW follows Part 6 and Subsection 3.6.5.

Materials OBC Div. B 9.33.6.2.. Ducts, connectors, fittings and plenums are noncombustible (steel, aluminum alloy, copper, clay or similar) unless an exception applies:

Exception	Limits
Combustible ducts	Class 1 to CAN/ULC-S110; meet 3.1.5.18. and 3.1.9.; not in vertical runs serving more than 2 storeys; not where air may exceed 120°C
Combustible duct connectors	Class 1; not more than 4 m long; horizontal runs only; not through required fire separations
Ventilation-only ducts inside one dwelling unit	Exempt from the material rules
Return ducts inside one dwelling unit	Exempt, except near the furnace and for solid-fuel furnaces

Duct sealants: flame-spread rating not more than 25 and smoke developed classification not more than 50. Duct tape: meets CAN/ULC-S109 OBC Div. B 9.33.6.3..

Foamed plastic insulation is generally not used on ducts. It is allowed on metal ducts if at least 3 m from the furnace bonnet on supply runs, duct air not over 50°C, joints taped, return plenums separated, and the foam protected under 9.10.17.10. OBC Div. B 9.33.6.4..

Metal thickness comes from the duct thickness table OBC Div. B Table 9.33.6.5.. Example values: a round galvanized duct of 125 mm or less serving a single dwelling unit needs 0.254 mm; a round galvanized duct up to 350 mm needs 0.33 mm.

Construction and installation OBC Div. B 9.33.6.6. OBC Div. B 9.33.6.7.:

Firestop the space around supply ducts in walls and floors with noncombustible material at each end.
Support ducts with metal hangers, straps, lugs or brackets (wood only where zero clearance is allowed).
Lap round joints at least 25 mm; use S and drive cleats on rectangular joints.
Do not nail trunk ducts directly to wood.
Garage duct systems are not interconnected with the rest of the dwelling unit.
Combustible ducts in slabs stay at least 600 mm from the furnace supply plenum.
Supply or return ducts exposed to unheated space are insulated to at least RSI 2.1.
Ducts in unconditioned space or outdoors are sealed to SMACNA Class A; supply ducts in conditioned space to Class C.

Plenum clearances OBC Div. B 9.33.6.8.:

Plenum clearance	Near the plenum	Farther out
75 mm or less	Same as plenum, within 450 mm	At least 12 mm beyond 450 mm (zero after a shielding bend)
Over 75 mm, up to 150 mm	Same as plenum, within 1.8 m	At least 12 mm beyond 1.8 m (zero after a shielding bend)
Over 150 mm	Same as plenum within 1 m; 150 mm from 1 m to 1.8 m	At least 25 mm beyond 1.8 m (8 mm after a shielding bend)

Supply outlets and returns:

Balancing dampers at the boot, or lockable adjustable diffusers OBC Div. B 9.33.6.9..
Combustible grilles: flame spread not more than 200 in bathrooms, 150 elsewhere OBC Div. B 9.33.6.10..
Grilles stop a 15 mm sphere; exterior screens have openings not larger than 15 mm OBC Div. B 9.33.6.10A..
A supply outlet in each finished room next to unheated space; one per 40 m² of unfinished basement; one per 80 m² of heated crawl space; not more than 3 kW per outlet; supply air not over 70°C OBC Div. B 9.33.6.11..
At least one return inlet per floor level (levels within 900 mm of a level with a return excepted); none in a room that provides combustion air to the furnace OBC Div. B 9.33.6.12..
Return system handles the entire supply; return ducts within 600 mm of the furnace casing (where exposed to radiation) are noncombustible; vertical returns open on not more than one floor; no recirculating return air between dwelling units OBC Div. B 9.33.6.13..
Filters are Class 2 to CAN/ULC-S111; electrostatic filters de-energize when the access door opens or the fan stops OBC Div. B 9.33.6.14..
Exhaust ducts discharge outdoors, resist back draft, and dryer ducts are independent OBC Div. B 9.33.6.14A..

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Radiators, convectors and piping

Radiators and convectors in a recess or on a combustible wall need a noncombustible lining or backing OBC Div. B 9.33.7.1..
Exposed radiator surfaces do not exceed 70°C unless contact is prevented OBC Div. B 9.33.7.2..
Pipes allow for expansion and contraction; supports must not overstress the structure OBC Div. B 9.33.8.1..
Pipe insulation above 120°C fluid is noncombustible or passes ASTM C411; exposed pipe surfaces do not exceed 52°C OBC Div. B 9.33.8.2..
Bare pipe clearances: none up to 95°C, 15 mm above 95°C to 120°C, 25 mm above 120°C OBC Div. B Table 9.33.8.3..
Pipes above 120°C through combustible construction get a noncombustible sleeve at least 50 mm larger in diameter; pipes through storage spaces get 25 mm of noncombustible insulation OBC Div. B 9.33.8.4..

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Refrigerating systems and equipment

A cooling unit sharing a duct system with a fuel-fired furnace is installed in parallel with the furnace, upstream (if the furnace is designed for it), or downstream (if the cooling unit is designed to prevent excessive temperature or pressure in the refrigeration system) OBC Div. B 9.33.9.1..

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Chimneys and venting equipment

Products of combustion from oil, gas and solid-fuel appliances are vented under the applicable appliance installation standard OBC Div. B 9.33.10.1.. Factory-built chimneys for solid fuel follow Sentence 9.21.1.3.(1) OBC Div. B 9.33.10.2.. Masonry or concrete chimneys follow Section 9.21. OBC Div. B 9.33.10.3..

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Common traps

Mixing the radiator limit (70°C) with the exposed pipe limit (52°C).
Using 80 m² for basements. Basements are 40 m² per outlet; heated crawl spaces are 80 m².
Assuming combustible duct connectors may be any length. The cap is 4 m, horizontal only.

Chapter review

Chapter at a glance

One line per section: the idea to carry into the exam. Then the answers that most often catch candidates out.

Chapter at a glance: the key idea in each section
Section	Key idea
Air duct systems	Duct sealants: flame-spread rating not more than 25 and smoke developed classification not more than 50. Duct tape: meets CAN/ULC-S109.
Refrigerating systems and equipment	A cooling unit sharing a duct system with a fuel-fired furnace is installed in parallel with the furnace, upstream (if the furnace is designed for it), or downstream (if the…
Chimneys and venting equipment	Products of combustion from oil, gas and solid-fuel appliances are vented under the applicable appliance installation standard.

Air duct systems
Duct sealants: flame-spread rating not more than 25 and smoke developed classification not more than 50. Duct tape: meets CAN/ULC-S109.
Refrigerating systems and equipment
A cooling unit sharing a duct system with a fuel-fired furnace is installed in parallel with the furnace, upstream (if the furnace is designed for it), or downstream (if the…
Chimneys and venting equipment
Products of combustion from oil, gas and solid-fuel appliances are vented under the applicable appliance installation standard.

Usual exam traps

Mixing the radiator limit (70°C) with the exposed pipe limit (52°C).
Using 80 m² for basements. Basements are 40 m² per outlet; heated crawl spaces are 80 m².
Assuming combustible duct connectors may be any length. The cap is 4 m, horizontal only.

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Questions on Ducts, piping, refrigeration and venting (9.33.6 to 9.33.10), in the exam format, every answer explained and cited to its article. Sign in to start; a free account gets the free questions.

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Code cited in this chapter

Based on the official 2024 Building Code Compendium on ontario.ca.

OBC Div. B 9.33.6.1. Application
(1)The requirements of this Subsection apply to the design, construction and installation of air duct distribution systems serving heating, ventilating and air-conditioning systems that serve an individual dwelling unit within the scope of Part 9.
(2)Air duct distribution systems in which the rated heat input exceeds 120 kW shall conform to Part 6 and Subsection 3.6.5.
Open OBC Div. B 9.33.6.1. in the code viewer
OBC Div. B 9.33.6.2. Materials in Air Duct Systems
(1)Except as provided in Sentences (2) to (6.2) and in 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 similar noncombustible material.
(2)Ducts, associated fittings and plenums are permitted to contain combustible material provided they
(a)conform to the appropriate requirements for Class 1 duct materials in CAN/ULC-S110, "Standard Methods of Test for Air Ducts,"
(b)conform to Article 3.1.5.18. and Subsection 3.1.9.,
(c)are not used in vertical runs serving more than 2 storeys, and
(d)are not used in air duct systems in which the air temperature may exceed 120°C.
(3)Duct sealants shall have a flame-spread rating of not more than 25 and a smoke developed classification of not more than 50.
(4)Duct connectors that contain combustible materials and that are used between ducts and air outlet units shall
(a)conform to the appropriate requirements for Class 1 air duct materials in CAN/ULC-S110, "Standard Methods of Test for Air Ducts,"
(b)be limited to 4 m in length,
(c)be used only in horizontal runs, and
(d)not penetrate required fire separations.
(5)Combustibleducts that are part of a duct system carrying only ventilation air and that are contained entirely within a dwelling unit need not comply with the requirements of Sentences (1) to (4).
(6)Except as provided in Sentences 9.33.6.13.(2) and (3), ducts that are part of a return-air duct system and that are contained entirely within a dwelling unit need not comply with the requirements of Sentences (1) to (4).
(6.1)All ductwork and fittings shall be constructed and installed in conformance with SMACNA Manuals and ASHRAE Handbooks.
(6.2)All duct materials and fittings shall be
(a)suitable for exposure to the temperature and humidity of the air being conveyed, and
(b)resistant to corrosion due to contaminants in the air being conveyed in the duct.
(7)Materials referred to in Sentences (1) to (6.2), when used in a location where they may be subjected to excessive moisture, shall
(a)have no appreciable loss of strength when wet, and
(b)be corrosion-resistant.
Open OBC Div. B 9.33.6.2. in the code viewer
OBC Div. B 9.33.6.3. Tape
(1)Tape used for sealing joints in air ducts, plenums and other parts of air duct systems shall meet the flame-resistance requirements for fabric in CAN/ULC-S109, "Standard Method for Flame Tests of Flame-Resistant Fabrics and Films."
Open OBC Div. B 9.33.6.3. in the code viewer
OBC Div. B 9.33.6.4. Coverings, Linings and Insulation
(1)Reserved.
(2)Reserved.
(3)Reserved.
(4)Reserved.
(5)Except as permitted in Sentences (6) and (7), foamed plastic insulation shall not be used as part of an air duct or for insulating an air duct.
(6)Foamed plastic insulation conforming to Article 9.25.2.2. is permitted to be used to insulate a galvanized steel, stainless steel or aluminum air duct, provided
(a)the foamed plastic insulation applied to supply ductwork is not less than 3 m from the furnace bonnet,
(b)the temperature within the ductwork where the insulation is installed is not greater than 50°C,
(c)duct joints are taped with a product conforming to Sentence 9.33.6.3.(1),
(d)return air plenums are separated from the foamed plastic insulation, and
(e)the foamed plastic insulation is protected in accordance with Article 9.10.17.10.
(7)Foamed plastic insulation is permitted to be used in a ceiling space that acts as a return air plenum provided the foamed plastic insulation is protected from exposure to the plenum in accordance with Sentence 3.1.5.14.(4).
(8)Reserved.
(9)Linings of ducts 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.
Open OBC Div. B 9.33.6.4. in the code viewer
OBC Div. B Table 9.33.6.5. Minimum Metal Thickness, mm
Table 9.33.6.5. — Minimum Metal Thickness, mm Forming Part of Article 9.33.6.5. Type of Duct | Maximum Diameter, mm | Maximum Width or Depth, mm | Duct Material: Galvanized Steel | Duct Material: Aluminum Round ducts serving single dwelling units | 125 or less | N/A | 0.254 | 0.30 Round | 350 | N/A | 0.33 | 0.30 Round | Over 350 | N/A | 0.41 | 0.41 Rectangular, enclosed | N/A | 350 | 0.33 | 0.30 Rectangular, enclosed | N/A | Over 350 | 0.41 | 0.41 Rectangular, not enclosed, with required clearance up to 12 mm | N/A | 350 | 0.33 | 0.41 Rectangular, not enclosed, with required clearance up to 12 mm | N/A | Over 350 | 0.41 | 0.48 Rectangular, not enclosed, with required clearance of more than 12 mm | N/A | 350 | 0.41 | 0.41 Rectangular, not enclosed, with required clearance of more than 12 mm | N/A | Over 350 | 0.48 | 0.48
Open OBC Div. B Table 9.33.6.5. in the code viewer
OBC Div. B 9.33.6.6. Construction of Ducts and Plenums
(1)Where the installation of heating supply ducts in walls and floors creates a space between the duct and construction material, the space shall be firestopped with noncombustible material at each end.
(2)Ducts shall be securely supported by metal hangers, straps, lugs or brackets, except that, where zero clearance is permitted, wooden brackets are permitted to be used.
(3)All round duct joints shall be tight-fitting and lapped not less than 25 mm.
(4)Rectangular duct connections shall be made with S and drive cleats or equivalent mechanical connections.
(4.1)Rectangular panels in plenums and ducts more than 300 mm wide shall be shaped to provide sufficient stiffness.
(5)Duct systems shall have no openings other than those required for the proper operation and maintenance of the system.
Open OBC Div. B 9.33.6.6. in the code viewer
OBC Div. B 9.33.6.7. Installation of Ducts and Plenums
(1)Air duct systems serving garages shall not be interconnected with other parts of the dwelling unit.
(2)Trunk supply ducts shall not be nailed directly to wood members.
(3)Branch ducts shall be supported at suitable spacings to maintain alignment and prevent sagging.
(4)Ducts passing through unheated spaces shall have all joints taped or otherwise sealed to ensure that the ducts are airtight throughout their length.
(5)Combustibleducts in concrete slabs-on-ground that are connected to a furnace supply plenum shall be located not closer than 600 mm to that plenum and not less than 600 mm from its connection to a riser or register.
(6)Ducts in or beneath concrete slabs-on-ground shall be watertight and corrosion-, decay-, and mildew-resistant.
(7)Underground ducts shall
(a)be constructed to provide interior drainage from and access to all low points,
(b)not be connected directly to a sewer, and
(c)be installed and constructed of materials in conformance with ASHRAE Handbooks, SMACNA Manuals and the HRAI Digest.
(8)Where a supply duct or return duct is not protected by an insulated exterior wall or where the duct is exposed to an unheated space it shall be insulated to provide a thermal resistance of not less than RSI 2.1.
(9)Where a supply duct or return duct is located in an unconditioned space or outdoors, all joints of the ductwork shall be sealed to a Class A seal level in accordance with the SMACNA, "HVAC Duct Construction Standards Metal and Flexible".
(10)Where a supply duct is located in a conditioned space, the ductwork shall be sealed to a Class C seal level in accordance with the SMACNA, "HVAC Duct Construction Standards Metal and Flexible".
(11)A clean-out or pump-out connection shall be provided in an underground duct system at every low point of the duct system.
Open OBC Div. B 9.33.6.7. in the code viewer
OBC Div. B 9.33.6.8. Clearances of Ducts and Plenums
(1)Reserved.
(2)Where the plenum clearance is 75 mm or less, the clearance between a supply duct and combustible material shall
(a)be equal to the required plenum clearance within 450 mm of the plenum, and
(b)be not less than 12 mm at a distance of 450 mm or more from the plenum, except that this clearance may 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))
(3)Where the plenum clearance is more than 75 mm but not more than 150 mm, the clearance between a supply duct and combustible material shall be
(a)equal to the required plenum clearance within a horizontal distance of 1.8 m of the plenum, and
(b)not less than 12 mm at a horizontal distance of 1.8 m or more from the plenum, except that this distance may be reduced to zero beyond a bend or offset in the duct sufficiently large to shield the remainder of the duct from direct radiation from the furnace heat exchanger. (See Note A-3.6.5.6.(3))
(4)Where the plenum clearance is more than 150 mm, the clearance between a supply duct and combustible material shall be
(a)equal to the required plenum clearance within a horizontal distance of 1 m of the plenum,
(b)not less than 150 mm within a horizontal distance between 1 m and 1.8 m from the plenum, and
(c)not less than 25 mm at a horizontal distance of 1.8 m or more from the plenum, except that this distance may 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))
(5)Where 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 in lieu of the clearances listed in Sentences (2) to (4).
Open OBC Div. B 9.33.6.8. in the code viewer

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OBC Div. B 9.33.6.9. Adjustable Dampers and Balance Stops
(1)All branch supply ducts for residential systems shall be equipped with volume control dampers at the boot to permit balancing or shall be fitted with a diffuser incorporating an adjustable and lockable volume control device that can be set in a fixed position.
Open OBC Div. B 9.33.6.9. in the code viewer
OBC Div. B 9.33.6.10. Warm-Air Supply Outlets and Return Inlets — General
(1)Reserved.
(2)Combustiblegrilles, diffusers and other devices for the supply and return air openings installed in walls and ceilings shall have a flame-spread rating of
(a)not more than 200 in bathrooms, and
(b)not more than 150 in rooms or spaces other than bathrooms.
Open OBC Div. B 9.33.6.10. in the code viewer
OBC Div. B 9.33.6.10A. Supply, Return, Intake and Exhaust Openings
(1)Supply, return and exhaust air openings in rooms or spaces shall be protected by grilles having openings of a size that will not allow the passage of a 15 mm diameter sphere.
(2)Outdoor air intakes and exhaust outlets at the building exterior shall be designed or located so that the air entering the building system will not contain more contaminants than the normal exterior air.
(3)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 climatic conditions may require larger openings.
(4)Screens required in Sentence (3) shall be accessible for maintenance.
Open OBC Div. B 9.33.6.10A. in the code viewer
OBC Div. B 9.33.6.11. Warm-Air Supply Outlets
(1)In a dwelling unit, a warm-air supply outlet shall be provided in each finished room that is located adjacent to unheated space.
(2)Except as provided in Sentence (3), when a room described in Sentence (1) is located adjacent to exterior walls, such outlet shall be located so as to bathe at least one exterior wall or window with warm air, except in bathrooms, utility rooms or kitchens, where this may not be practical.
(3)Where the heating system is also designed to provide ventilation air, ceiling outlets or outlets located high on interior walls are permitted to be installed, provided the outlets are designed for this purpose and are installed with diffusers.
(4)At least one warm-air supply outlet shall be provided for each 40 m² of floor surface area in unfinished basements serving dwelling units, and it shall be located so as to provide adequate distribution of warm air throughout the basement.
(5)At least one warm-air supply outlet shall be provided for each 80 m² of floor surface area in heated crawl spaces serving dwelling units, and it shall be located so as to provide adequate distribution of warm air throughout the crawl space.
(6)Except for pipeless furnaces and floor furnaces, the capacity of warm-air supply outlets serving dwelling units shall be not less than the design heat loss from the area served and shall not exceed 3 kW per outlet.
(7)In basements and heated crawl spaces, the calculated heat gain from the supply ducts and plenum surfaces is permitted to be considered in calculating the design heat loss.
(8)The temperature of supply air at warm-air supply outlets shall not exceed 70°C.
(9)Warm-air supply outlets located in finished areas shall be provided with diffusers and adjustable openings and shall not be located on a furnace plenum.
(10)Air duct systems serving storage garages shall not be interconnected with other parts of the building.
Open OBC Div. B 9.33.6.11. in the code viewer
OBC Div. B 9.33.6.12. Return-Air Inlets
(1)Return-air inlets shall not be installed in an enclosed room or crawl space that provides combustion air to a furnace.
(2)Except for floor levels which are less than 900 mm above or below an adjacent floor level which is provided with a return-air inlet, at least one return-air inlet shall be provided in each floor level in a dwelling unit.
(3)Provision shall be made for the return of air from all rooms by leaving gaps beneath doors, using louvred doors or installing return duct inlets.
Open OBC Div. B 9.33.6.12. in the code viewer
OBC Div. B 9.33.6.13. Return-Air System
(1)The return-air system shall be designed to handle the entire air supply.
(1.1)Except as provided in Sentences (2) and (3), return ducts shall be constructed of material having a surface flame-spread rating of not more than 150.
(2)Where any part of a return duct will be exposed to radiation from the furnace heat exchanger or other radiating part within the furnace, such part of a return duct directly above or within 600 mm of the outside furnace casing shall be noncombustible.
(3)Return ducts serving solid-fuel-burning furnaces shall be constructed of noncombustible material.
(4)Combustible return ducts shall be lined with noncombustible material
(a)below floor registers,
(b)at the bottom of vertical ducts, and
(c)under furnaces having a bottom return.
(5)Spaces between studs or joists used as return ducts shall be separated from the unused portions of such spaces by tight-fitting metal stops or wood blocking.
(6)A vertical return duct shall have openings to return air on not more than one floor.
(6.1)A public corridor shall comply with Sentences 6.3.2.7.(4) and (5).
(7)The return-air system shall be designed so that the negative pressure from the circulating fan cannot
(a)affect the furnace combustion air supply, nor
(b)draw combustion products from joints or openings in the furnace or flue pipe.
(7.1)Return-air from a dwelling unit shall not be recirculated to any other dwelling unit.
Open OBC Div. B 9.33.6.13. in the code viewer
OBC Div. B 9.33.6.14. Filters and Odour Removal Equipment
(1)Air filters for air duct systems shall conform to the requirements for Class 2 air filter units as described in CAN/ULC-S111, "Standard Method of 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.
(3)When odour removal equipment of the adsorption type is used it shall be
(a)installed to provide access so that adsorption material can be reactivated or renewed, and
(b)protected from dust accumulation by air filters installed on the inlet side.
Open OBC Div. B 9.33.6.14. in the code viewer
OBC Div. B 9.33.6.14A. Exhaust Ducts and Outlets
(1)Where an exhaust duct passes through or is adjacent to unheated space, the duct shall be insulated to prevent moisture or condensation in the duct.
(2)Exhaust outlets shall be designed to prevent back draft under wind conditions.
(3)Exhaust ducts directly connected to laundry drying equipment shall be independent of other exhaust ducts.
(4)Exhaust systems shall discharge directly to the outdoors.
Open OBC Div. B 9.33.6.14A. in the code viewer
OBC Div. B 9.33.7.1. Recessed Radiators and Convectors
(1)Every steam or hot water radiator and convector located in a recess or concealed space or attached to the face of a wall of combustible construction shall be provided with a noncombustible lining or backing.
Open OBC Div. B 9.33.7.1. in the code viewer
OBC Div. B 9.33.7.2. Surface Temperature
(1)The exposed surface temperature of a steam or hot water radiator shall not exceed 70°C unless precautions are taken to prevent human contact.
Open OBC Div. B 9.33.7.2. in the code viewer
OBC Div. B 9.33.8.1. Piping Materials and Installation
(1)Piping shall be made from materials designed to withstand the effects of temperatures and pressures that may occur in the system. (See Articles 3.1.5.19., 3.1.9.1. and 9.10.9.7., and Sentence 9.10.9.9.(3) for fire safety requirements.)
(2)Every pipe used in a heating or air-conditioning system shall be installed to allow for expansion and contraction due to temperature changes.
(3)Supports and anchors for piping in a heating or air-conditioning system shall be designed and installed to ensure that undue stress is not placed on the supporting structure.
Open OBC Div. B 9.33.8.1. in the code viewer
OBC Div. B 9.33.8.2. Insulation and Coverings
(1)Insulation and coverings on pipes shall be composed of material suitable for the operating temperature of the system to withstand deterioration from softening, melting, mildew and mould.
(2)Insulation and coverings on pipes in which the temperature of the fluid exceeds 120°C
(a)shall be made of noncombustible material, or
(b)shall not flame, glow, smoulder or smoke when tested in accordance with ASTM C411, "Standard Specification for Hot-Surface Performance of High-Temperature Thermal Insulation," at the maximum temperature to which such insulation or covering is to be exposed in service.
(3)Except as provided in Sentence (6), where combustible insulation is used on piping in a horizontal or vertical service space, the insulation and coverings on such pipes shall have a flame-spread rating throughout the material of not more than
(a)25 in buildings of noncombustible construction, and
(b)75 in buildings of combustible construction.
(4)Except as provided in Sentence (6), insulation and coverings on piping located in rooms and spaces other than the service spaces described in Sentence (3) shall have a flame-spread rating not more than that required for the interior finish for the ceiling of the room or space.
(5)Pipes that are exposed to human contact shall be insulated so that the exposed surface does not exceed 52°C. (See Note A-6.5.1.1.(3))
(6)No flame-spread rating or smoke developed classification limitations are required where combustible insulation and coverings are used on piping when such piping is
(a)located within a concealed space in a wall,
(b)located in a floor slab, or
(c)enclosed in a noncombustible raceway or conduit.
Open OBC Div. B 9.33.8.2. in the code viewer
OBC Div. B Table 9.33.8.3. Clearance Between Steam or Hot Water Pipes and Combustible Material - Forming Part of Sentence 9.33.8.3.(1)
Table 9.33.8.3. Clearance Between Steam or Hot Water Pipes and Combustible Material - Forming Part of Sentence 9.33.8.3.(1) Forming Part of Sentence 9.33.8.3.(1) Steam or Water Temperature (T), °C | Minimum Clearance, mm T ≤ 95 | No clearance required. 95 < T ≤ 120 | 15 T > 120 | 25
Open OBC Div. B Table 9.33.8.3. in the code viewer
OBC Div. B 9.33.8.4. Protection
(1)Where a pipe carrying steam or hot water at a temperature above 120°C passes through a combustible floor, ceiling or wall, the construction shall be protected by a sleeve of metal or other noncombustible material not less than 50 mm larger in diameter than the pipe.
(2)Unprotected steam or hot water pipes that pass through a storage space shall be covered with not less than 25 mm thickness of noncombustible insulation to prevent direct contact with the material stored.
Open OBC Div. B 9.33.8.4. in the code viewer
OBC Div. B 9.33.9.1. Cooling Units
(1)Where a cooling unit is combined with a fuel-fired furnace in the same duct system, the cooling unit shall be installed
(a)in parallel with the heating furnace,
(b)upstream of the furnace, provided the furnace is designed for such application, or
(c)downstream of the furnace, provided the cooling unit is designed to prevent excessive temperature or pressure in the refrigeration system.
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OBC Div. B 9.33.10.1. Requirement for Venting
(1)Except as provided in Articles 9.33.10.2. and 9.33.10.3., the products of combustion from oil-, gas- and solid-fuel-burning appliances, including stoves, cooktops, ovens and space heaters, shall be vented in conformance with the applicable appliance installation standard listed in Sentences 9.33.5.2.(1) and 9.33.5.3.(1).
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OBC Div. B 9.33.10.2. Factory-Built Chimneys
(1)Factory-built chimneys serving solid-fuel-burning appliances, and their installation, shall comply with Sentence 9.21.1.3.(1). (See Note A-9.33.10.2.(1))
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OBC Div. B 9.33.10.3. Masonry or Concrete Chimneys
(1)Masonry or concrete chimneys shall conform to Section 9.21.
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