Cover [PDF]

Preface and Acknowledgements [PDF]

California Code of Regulations, Title 24 [PDF]

How to Distinguish Between Model Code Language and California Amendments [PDF]

How to Distinguish Model Code Language from California Amendments [PDF]

Foreword [PDF]

Format of the Uniform Mechanical Code [PDF]

Committee on Uniform Mechanical Code [PDF]

Section Relocation [PDF]

Table of Contents [PDF]

Chapter 1 Administration

Chapter 2 Definitions

Chapter 3 General Regulations

Chapter 4 Ventilation Air

Chapter 5 Exhaust Systems

Chapter 6 Duct Systems

Chapter 7 Combustion Air

Chapter 8 Chimneys and Vents

Chapter 9 Installation of Specific Appliances

Chapter 10 Boilers and Pressure Vessels

Chapter 11 Refrigeration

Chapter 12 Hydronics

Chapter 13 Fuel Gas Piping

Chapter 14 Process Piping

Chapter 15 Solar Energy Systems

Chapter 16 Stationary Power Plants

Chapter 17 Referenced Standards

Appendices [PDF]

Appendix A Residential Plan Examiner Review Form for HVAC System Design

Appendix B Procedures to be Followed to Place Gas Equipment in Operation

Appendix C Installation and Testing of Oil (Liquid) Fuel-Fired Equipment

Appendix D Fuel Supply: Manufactured/Mobile Home Parks and Recreational Vehicle Parks

Appendix E Sustainable Practices

Appendix F Sizing of Venting Systems and Outdoor Combustion and Ventilation Opening Design

Appendix G Example Calculation of Outdoor Air Rate

Index [PDF]

History Note Appendix [PDF]

Ducts and plenums that are portions of a heating, cooling, absorption or evaporative cooling, or exhaust system shall comply with the requirements of this chapter.
Duct systems used with blower-type equipment that are portions of a heating, cooling, absorption, evaporative cooling, or outdoor-air ventilation system I shall be sized in accordance with an approved standard listed in Table 1701.1, or by other approved methods.

Exception: [HCD 1 & HCD 2] Duct sizing calculations are not required for existing duct systems.
Supply air, return air, and outside air for heating, cooling, or evaporative cooling duct systems constructed of metal shall comply with SMACNA HVAC Duct Construction Standards-Metal and Flexible or UL 181.

Exception: [OSHPD 1, 2, 3 & 4] See Section 407.4.1.3

    Not permitted for [OSHPD 1, 2, 3 & 4] Concealed building spaces or independent construction within buildings shall be permitted to be used as ducts or plenums.
Materials exposed within ducts or plenums shall be noncombustible or shall have a flame spread index not to exceed 25 and a smoke developed index not to exceed 50, where tested as a composite product in accordance with ASTM E84 or UL 723.

Exceptions:
  1. Return-air and outside-air ducts, plenums, or concealed spaces that serve a dwelling unit shall be permitted to be of combustible construction.
  2. Air filters in accordance with the requirements of Section 311.2.
  3. Water evaporation media in an evaporative cooler.
  4. Charcoal filters where protected with an approved fire suppression system.
  5. Products listed and labeled for installation within plenums in accordance with Section 602.2.1 through Section 602.2.4.
  6. Smoke detectors.
  7. Duct insulation, coverings, and linings and other supplementary materials installed in accordance with Section 604.0.
  8. Materials in a hazardous fabrication area including the areas above and below the fabrication area sharing a common air recirculation path with the fabrication area.
Electrical wiring in plenums shall comply with NFPA 70. Electrical wires and cables and optical fiber cables shall be listed and labeled for use in plenums and shall have a flame spread distance not exceeding 5 feet (1524 mm), an average optical density not exceeding 0.15, and a peak optical density not exceeding 0.5, where tested in accordance with NFPA 262.
Nonmetallic fire sprinkler piping in plenums shall be listed and labeled for use in plenums and shall have a flame spread distance not exceeding 5 feet (1524 mm), an average optical density not exceeding 0.15 and, a peak optical density not exceeding 0.5, where tested in accordance with UL 1887.
Nonmetallic pneumatic tubing in plenums shall be listed and labeled for use in plenums and shall have a flame spread distance not exceeding 5 feet (1524 mm), an average optical density not exceeding 0.15, and a peak optical density not exceeding 0.5, where tested in accordance with UL 1820.
Loudspeakers and recessed lighting fixtures, including their assemblies and accessories, in plenums shall be listed and labeled for use in plenums and shall have a peak rate of heat release not exceeding 134 horsepower (hp) (100 kW), an average optical density not exceeding 0.15, and a peak optical density not exceeding 0.5, where tested in accordance with UL 2043.
Discrete plumbing, mechanical, and electrical products that are located in a plenum and have exposed combustible material shall be in accordance with UL 2043.
Ducts, plenums, or fittings of metal shall comply with SMACNA HVAC Duct Construction Standards-Metal and Flexible.
Existing metal ducts shall be permitted to be used where cooling coils are added to a heating system, provided the first 10 feet (3048 mm) of the duct or plenum measured from the cooling coil discharge are constructed of metal of the gauge thickness in accordance with SMACNA HVAC Duct Construction Standards- Metal and Flexible. Existing metal ducts completely enclosed in inaccessible concealed areas are not required to be replaced. Accessible ducts shall be insulated in accordance with Section 604.0. For the purpose of this section, ducts shall be considered accessible where the access space is 30 inches (762 mm) or more in height.
Where gypsum products are exposed in ducts or plenums, the air temperature shall be restricted to a range from 50°F (10°C) to 125°F (52°C), and moisture content shall be controlled so that the material is not adversely affected. For the purpose of this section, gypsum products shall not be exposed in ducts serving as supply from evaporative coolers, and in other air-handling systems regulated by this chapter where the temperature of the gypsum product will be below the dew point temperature.
Factory-made air ducts shall be approved for the use intended or shall be in accordance with the requirements of UL 181. Each portion of a factory-made air duct system shall be identified by the manufacturer with a label or other identification indicating compliance with its class designation.
[OSHPD 1, 2, 3, & 4] In hospital building projects and all other health-care facilities, including clinics and correctional treatment centers, flexible ducts of not more than 10 feet (3048 mm) in length may be used to connect supply, return or exhaust-air terminal devices to rigid duct systems. Where constant volume, variable volume or mixing boxes are utilized, flexible duct of not more than 10 feet (3048 mm), may be used on the inlet side for alignment. An internal impervious liner shall be provided to isolate insulation materialfrom conditioned air.
Vibration isolators installed between mechanical equipment and metal ducts (or casings) shall be made of an approved material and shall not exceed 10 inches (254 mm) in length.
Corridors shall not be used to convey air to or from rooms where the corridor is required to be of fire-resistive construction in accordance with the building code except where pennitted by the building code.
The pressure classification of ducts shall be not less than the design operating pressure of the air distribution in which the duct is utilized.
Air ducts installed under a floor in a crawl space shall be installed in accordance with the following:
  1. Shall not prevent access to an area of the crawl space.
  2. Where it is required to move under ducts for access to areas of the crawl space, a vertical clearance of not less than 18 inches (457 mm) shall be provided.
Ducts shall be supported at each change of direction and in accordance with SMACNA HVAC Duct Construction Standards-Metal and Flexible. Riser ducts shall be held in place by means of metal straps or angles and channels to secure the riser to the structure.

    Metal ducts shall be installed with not less than 4 inches (102 mm) separation from earth. Ducts shall be installed in a building with clearances that will retain the full thickness of fireproofing on structural members.
Supports for rectangular ducts shall be installed on two opposite sides of each duct and shall be riveted, bolted, or metal screwed to each side of the duct at intervals specified.
Horizontal round ducts not more than 40 inches (1016 mm) in diameter where suspended from above shall be supported with one hanger per interval and in accordance with Section 603.3.2.1 through Section 603.3.2.3.
Ducts shall be equipped with tight-fitting circular bands extending around the entire perimeter of the duct at each specified support interval.
Circular bands shall be not less than 1 inch (25.4 mm) wide nor less than equivalent to the gauge of the duct material it supports.

Exception: Ducts not more than 10 inches (254 mm) in diameter shall be permitted to be supported by No. 18 gauge galvanized steel wire.
Each circular band shall be provided with means of connecting to the suspending support.
Ducts located in structures that are installed in areas classified as seismic design category C, D, E, or F shall be in accordance with the building code.
Factory-made air ducts and connectors shall be listed and labeled in accordance with UL 181 and installed in accordance with the terms of their listing, the manufacturer's installation instructions, and SMACNA HVAC Duct Construction Standards - Metal and Flexible.

    Factory-made air ducts shall not be used for vertical risers in air-duct systems serving more than two stories and shall not penetrate a fire-resistance-rated assembly or construction.

    Factory-made air ducts shall be installed with not less than 4 inches (102 mm) of separation from earth, except where installed as a liner inside of concrete, tile, or metal pipe and shall be protected from physical damage.

    The temperature of the air to be conveyed in a duct shall not exceed 250°F (121°C).
[Not permitted for OSHPD 1, 2, 3 & 4] Factory-made flexible air ducts and connectors shall be not more than 5 feet (1524 mm) in length and shall not be used in lieu of rigid elbows or fittings.

Exception: Residential occupancies.
Flexible air ducts and connectors shall comply with UL 181, and shall be installed in accordance with the manufacturer's installation instructions and SMACNA HVAC Duct Construction Standards-Metal and Flexible. Flexible air ducts shall not penetrate a fire-resistance-rated assembly or construction. Flexible air connector lengths shall be not more than 5 feet (1524 mm) and shall not penetrate a wall, floor, or ceiling. The temperature of the air to be conveyed in a flexible air duct or connector shall not exceed 250°F (121°C).
Plastic air ducts and fittings shall be permitted where installed underground and listed for such use.
Ducts installed in locations where they are exposed to mechanical damage by vehicles or from other causes shall be protected by approved barriers.
Installers shall provide the manufacturer's field fabrication and installation instructions.

    Factory-made air ducts that are in accordance with UL 181 shall be supported in accordance with the manufacturer's instructions. Other ducts shall comply with SMACNA HVAC Duct Construction Standards-Metal and Flexible.
In flood hazard areas, ducts shall be located above the elevation required by the building code for utilities and attendant equipment or the elevation of the lowest floor, whichever is higher, or shall be designed and constructed to prevent water from entering or accumulating within the ducts during floods up to such elevation. Where the ducts are located below that elevation, the ducts shall be capable of resisting hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during the occurrence of flooding to such elevation.
Joints and seams for duct systems shall comply with SMACNA HVAC Duct Construction Standards-Metal and Flexible. Joints of duct systems shall be made substantially airtight by means of tapes, mastics, gasketing, or other means. Crimp joints for round ducts shall have a contact lap of not less than 112 inches (38 mm) and shall be mechanically fastened by means of not less than three sheet-metal screws equally spaced around the joint, or an equivalent fastening method.

    Joints and seams and reinforcements for factory-made air ducts and plenums shall comply with the conditions of prior approval in accordance with the installation instructions that shall accompany the product. Closure systems for rigid air ducts and plenums shall be listed in accordance with UL 181A. Closure systems for flexible air ducts shall be listed in accordance with UL 181B.
Exhaust ducts and venting systems under positive pressure shall not extend into or pass through ducts or plenums.
Ducts installed underground shall be approved for the installation and shall have a slope of not less than 12 inch per foot (10.4 mm/m). Ducts, plenums, and fittings shall be permitted to be constructed of concrete, clay, or ceramics where installed in the ground or in a concrete slab, provided the joints are tightly sealed. Metal ducts where installed in or under a concrete slab shall be encased in not less than 2 inches (51 mm) of concrete.
Air ducts conveying air at temperatures exceeding 140°F (60°C) shall be insulated to maintain an insulation surface temperature of not more than 140°F (60°C). Factory-made air ducts and insulations intended for installation on the exterior of ducts shall be legibly printed with the name of the manufacturer, the thermal resistance (R) value at installed thickness, flame-spread index and smoke developed index of the composite material. Internal duct liners and insulation shall be installed in accordance with SMACNA HVAC Duct Construction Standards-Metal and Flexible. [OSHPD 1, 2, 3 & 4] Cold air ducts shall be insulated wherever necessary or to prevent condensation.

Exceptions:
  1. Factory-installed plenums, casings, or ductwork furnished as a part of HVAC equipment tested and rated in accordance with approved energy efficiency standards.
  2. Ducts or plenums located in conditioned spaces where heat gain or heat loss will not increase energy use.
  3. For runouts less than 10 feet (3048 mm) in length to air terminals or air outlets, the rated R value of insulation need not exceed R-3.5.
  4. Backs of air outlets and outlet plenums exposed to unconditioned or indirectly conditioned spaces with face areas exceeding 5 square feet (0.5 m2) need not exceed R-2; those 5 square feet (0.5 m2) or smaller need not be insulated.
  5. Ducts and plenums used exclusively for evaporative cooling systems.
Materials installed within ducts and plenums for insulating, sound deadening, or other purposes shall have a mold, humidity, and erosion-resistant surface where tested in accordance with UL 181. Duct liners in systems operating with air velocities exceeding 2000 feet per minute (10.16 m/s) shall be fastened with both adhesive and mechanical fasteners, and exposed edges shall have approved treatment to withstand the operating velocity. Where the internal insulation is capable of being in contact with condensates or other liquids, the material shall be water-resistant.
Insulation applied to the surface of ducts, including duct coverings, linings, tapes, and adhesives, located in buildings shall have a flame-spread index not to exceed 25 and a smoke developed index not to exceed 50, where tested in accordance with ASTM E84 or UL 723. The specimen preparation and mounting procedures of ASTM E2231 shall be used. Air duct coverings and linings shall not flame, glow, smolder, or smoke where tested in accordance with ASTM C411 at the temperature to which they are exposed in service. In no case shall the test temperature be less than 250°F (121°C). Coverings shall not penetrate a fire-resistance-rated assembly.
[OSHPD 1, 2, 3 (surgical clinics) & 4] Thermal acoustical lining materials shall not be installed within ducts, terminal boxes, should traps, and other in-duct systems serving areas such as operating, cesarean operating rooms, delivery rooms, post anesthesia care units, cystoscopy, cardiac catheterization labs, nurseries, intensive care units, newborn intensive care units, and airborne infection isolation rooms unless terminal filters with 90 percent average efficiency based on ASHRAE Standard 52.2 or minimum efficiency rating value (MERV) of 14 are installed downstream of the duct lining.
[OSHPD 1, 2 & 4] Thermal or acoustical lining materials shall not be installed within ducts which are downstream of the 99.97 percent high-efficiency particulate air (HEPA) filter or with minimum efficiency rating value (MERV) of 17 required in Section 408.2.1 for protective environment rooms.
Smoke dampers shall comply with UL 555S, and shall be installed in accordance with the manufacturer's installation instructions where required by the building code.
Fire dampers shall comply with UL 555, and shall be installed in accordance with the manufacturer's installation instructions where required by the building code. Fire dampers shall have been tested for closure under airflow conditions and shall be labeled for both maximum airflow permitted and direction of flow. Where more than one damper is installed at a point in a single air path, the entire airflow shall be assumed to be passing through the smallest damper area.

    Ductwork shall be connected to damper sleeves or assemblies in accordance with the fire damper manufacturer's installation instructions.
Ceiling radiation dampers shall comply with UL 555C, and shall be installed in accordance with the manufacturer's installation instructions in the fire-resistive ceiling element of floor-ceiling and roof-ceiling assemblies where required by the building code. Fire dampers not meeting the temperature limitation of ceiling radiation dampers shall not be used as a substitute.
Where size requires the use of multiple dampers, the installation shall be framed in an approved manner to ensure that the dampers remain in place.
Fire and smoke dampers shall be provided with an approved means of access large enough to allow inspection and maintenance of the damper and its operating parts. The access shall not affect the integrity of the fire resistance-rated assembly. The access openings shall not reduce the fire resistance rating of the assembly.

    Access shall not require the use of tools. Access doors in ducts shall be tight fitting and approved for the required duct construction. Access points shall be permanently identified on the exterior by a label with letters not less than 12 of an inch (12.7 mm) in height reading as one of the following:
  1. Smoke Damper
  2. Fire Damper
  3. Fire/Smoke Damper
Dampers shall be installed in a manner to ensure positive closing or opening as required by function. Interior liners or insulation shall be held back from portions of a damper, its sleeve, or adjoining duct that would interfere with the damper's proper operation. Exterior materials shall be installed so as to not interfere with the operation or maintenance of external operating devices needed for the function of the damper.
Fusible links, thermal sensors, and pneumatic or electric operators shall have a temperature rating or classification as in accordance with the building code.
When the automatic activation of a smoke damper or a combination smoke-fire damper occurs, the HVAC system serving such dampers shall immediately shut down.

Exceptions:
  1. HVAC systems that are part of an engineered smoke evacuation system.
  2. Where the automatic activation causes all the smoke dampers and combination smoke-fire dampers to close in the enclosed space having a common atmosphere where opcnings are requircd to be protected.
  3. Where analysis demonstrates shutoff would create a greater hazard.
The HVAC system shall not be restarted again until all the dampers are reset and fully opened.
Perforated ceilings shall be permitted to be used for air supply within the limitations of this section. Exit corridors, where required to be of fire-resistive construction by the building code, shall not have ventilating ceilings.
[OSHPD 1, 2, 3 & 4] Ventilating ceilings are not permitted in health facilities.
Ventilating ceilings shall comply with the following:
  1. Suspended ventilating ceiling material shall have a Class 1 flame-spread classification on both sides, determined in accordance with the building code. Suspended ventilating ceiling supports shall be of noncombustible materials.
  2. Lighting fixtures recessed into ventilating ceilings shall be of a type approved for that purpose.
An under-floor space shall be permitted to be used as a supply plenum.
The use of under-floor space shall be limited to dwelling units not more than two stories in height. Except for the floor immediately above the under-floor plenum, supply ducts shall be provided extending from the plenum to registers on other floor levels.

Exception: In flood hazard areas, under-floor spaces shall not be used as supply plenums unless the flood opening requirements in the building code are met.
Such spaces shall be cleaned of all loose combustible scrap material and shall be tightly enclosed.
The enclosing material of the under-floor space, including the sidewall insulation, shall be not more flammable than 1 inch (25.4 mm) (nominal) wood boards (flame-spread index of 200). Installation of foam plastics is regulated by the building code.
Access shall be through an opening in the floor and shall be not less than 24 inches by 24 inches (610 mm by 610 mm).
A furnace supplying warm air to under-floor space shall be equipped with an automatic control that will start the air-circulating fan where the air in the furnace bonnet reaches a temperature not exceeding 150°F (66°C). Such control shall be one that cannot be set to exceed 150°F (66°C).
A furnace supplying warm air to such space shall be equipped with an approved temperature limit control that will limit outlet air temperature to 200°F (93°C).
A noncombustible receptacle shall be placed below each floor opening into the air chamber, and such receptacle shall comply with Section 607.8.1 through Section 607.8.3.
The receptacle shall be securely suspended from the floor members and shall be not more than 18 inches (457 mm) below the floor opening.
The area of the receptacle shall extend 3 inches (76 mm) beyond the opening on all sides.
The perimeter of the receptacle shall have a vertical lip not less than 1 inch (25.4 mm) high at the open sides where it is at the level ofthe bottom of the joists, or 3 inches (76 mm) high where the receptacle is suspended.
Floor registers shall be designed for easy removal in order to give access for cleaning the receptacles.
Exterior walls and interior stud partitions shall be fireblocked at the floor.
Each wall register shall be connected to the air chamber by a register box or boot.
A duct complying with Section 602.0 shall extend from the furnace supply outlet not less than 6 inches (152 mm) below combustible framing.
The entire ground surface of the under-floor space shall be covered with a vapor barrier having a thickness not less than 4 mils (0.1 mm) and a flame-spread index of not more than 200.
Fuel gas lines and plumbing waste c1eanouts shall not be located within the space.
Airmoving systems supplying air in excess of 2000 cubic feet per minute (ft3/min) (0.9439 m3/s) to enclosed spaces within buildings shall be equipped with an automatic shutoff. Automatic shutoff shall be accomplished by interrupting the power source of the air-moving equipment upon detection of smoke in the main supply-air duct served by such equipment. Duct smoke detectors shall comply with UL 268A, shall be labeled by an approved agency, approved and listed by California State Fire Marshal, and shall be installed in accordance with the manufacturer's installation instructions. Such devices shall be compatible with the operating velocities, pressures, temperatures, and humidities of the system. Where fire-detection or alarm systems are provided for the building, the smoke detectors shall be supervised by such systems in an approved manner, and installed in accordance with NFPA 72 and the California Building and Fire Codes.

Exceptions:
  1. Where the space supplied by the air-moving equipment is served by a total coverage smoke-detection system in accordance with the California Fire Code, interconnection to such system shall be permitted to be used to accomplish the required shutoff.
  2. Automatic shutoff is not required where occupied rooms served by the air-handling equipment have direct exit to the exterior and the travel distance does not exceed 100 feet (30480 mm).
  3. Automatic shutoff is not required for Group R, Division 3 and Group U Occupancies.
  4. Automatic shutoff is not required for approved smoke-control systems or where analysis demonstrates shutoff would create a greater hazard, such as shall be permitted to be encountered in air-moving equipment supplying specialized portions of Group H Occupancies. Such equipment shall be required to have smoke detection with remote indication and manual shutoff capability at an approved location.
  5. Smoke detectors that are factory installed in listed air-moving equipment shall be permitted to be used in lieu of smoke detectors installed in the main supply-air duct served by such equipment.
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