CMC · California Mechanical Code
How are duct penetrations through fire/smoke barriers protected?
If a duct would let fire or smoke cross a protected wall, floor or smoke barrier, California code requires you to either enclose the duct in a shaft or install the correct listed damper(s) and properly seal the gap. For ducts through non‑rated floors the code allows three specific methods (shaft, short two‑story connection with annular sealing, or up to three stories with sealing plus fire dampers at each floor); bedrooms and dwelling‑unit ducts have limited exceptions.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
Ducts and air‑transfer openings that penetrate protected assemblies must be closed or enclosed so they do not defeat the fire‑ or smoke‑resistance of the assembly. Key control points are § 717.1.1, § 717.6.2, and § 717.6.3 of the California Building Code (CMC). § 717.1.1 lets ducts transition between shafts only if the penetration into each shaft is protected with compliant dampers. § 717.6.3 lists the allowed protection methods for ducts penetrating nonfire‑resistance‑rated floors (shaft enclosure, story‑limit exceptions, or damper at each floor line).
The single most important rule: where a duct would let fire or smoke cross a required barrier, the duct must either have the correct listed damper(s) or be enclosed/treated so the barrier’s rating and smoke control function are preserved.
Requirements in detail
Which assemblies and the basic options
- For ducts penetrating between shafts, a shaft enclosure is required unless the duct penetration into each shaft is protected with listed dampers meeting this section. (See § 717.1.1.)
- For penetrations of horizontal assemblies: either enclose the duct in a shaft enclosure (Section 713) or follow the rules in § 717.6.1–717.6.3 for alternative protection.
- For nonfire‑resistance‑rated floor assemblies, three alternative protection methods are allowed in § 717.6.3 (shaft enclosure; duct connecting ≤ two stories with annular space sealed with approved noncombustible material; or for noncombustible floors, duct connecting ≤ three stories if annular space sealed and a fire damper is installed at each floor line). (See § 717.6.3.)
Decision table — which protection to choose
| Decision dimension | Allowed protection / value | Code Reference |
|---|---|---|
| Duct transition between shafts | Provide listed dampers at the penetration into each shaft (no shaft enclosure required if dampers installed) | § 717.1.1. |
| Penetration of horizontal assembly | Enclose in shaft enclosure (§ 713) or comply with §§ 717.6.1–717.6.3 alternatives | § 717.6. |
| Nonfire‑rated floor: duct connects ≤ 2 stories | Annular space protected with approved noncombustible material that resists free passage of flame/smoke (no shaft required) | § 717.6.3 (method 2). |
| Nonfire‑rated floor: duct connects ≤ 3 stories (noncombustible floor assembly) | Annular space protected with approved noncombustible + fire damper at each floor line | § 717.6.3 (method 3). |
| Shaft enclosure permitted option | Use shaft complying with § 713 (then penetrations comply with § 717) | § 717.6 and § 713. |
| Exception for dwelling units | Fire dampers are not required in ducts within individual residential dwelling units | § 717.6.3 exception. |
Damper types & actuation (summary)
- Fire dampers — required where duct penetrations would otherwise reduce the fire‑resistance of walls/barriers, except where specific exceptions apply. Fire damper actuation must meet the listed temperature-release criteria.
- Smoke dampers — required where ducts penetrate smoke barriers or where a damper is needed to resist smoke passage; smoke dampers must be actuated by listed smoke detectors per the actuation rules (detector location within 5 feet of damper when installed in duct).
- Combination fire/smoke dampers — permitted where both fire and smoke control functions are required; actuation must satisfy both fire and smoke rules.
(Full test/labeling and installation requirements for dampers are in the damper testing and installation sections; see Related provisions below.)
Exceptions & special cases
- Ducts used as part of an approved smoke control system: dampers that would interfere with smoke control operation are not required; approved alternative protection must be used. (See § 717.2.1 and the exceptions in § 717.5.x.)
- If the penetration is tested as part of the fire‑resistance‑rated assembly (ASTM E119 / UL 263), fire dampers are not required at that penetration.
- For some occupancies and configurations (e.g., certain shaft penetrations in parking garages, continuously ventilated exhaust shafts with minimum steel subduct thickness and continuous upward airflow) specific exceptions apply; check the exception text in the code.
- Residential units — fire dampers are not required in ducts wholly within an individual dwelling unit per § 717.6.3 exception.
Common mistakes
- Assuming any duct shaft transition can be left open — ducts transitioning between shafts must still have dampers at each shaft penetration unless the shaft is continuous and constructed per § 713 or the shaft is omitted under the § 717.1.1 allowance with dampers.
- Using a fire damper where a smoke damper is required (and vice versa) — where both fire and smoke protection is required provide a combination fire/smoke damper or both devices. Actuation/testing requirements differ.
- Failing to seal the annular space to resist free passage of flame/products of combustion when relying on the annular‑space methods in § 717.6.3. The code requires an approved material that resists free passage of flame and products of combustion.
- Forgetting access and labeling — dampers requiring inspection must have approved access (minimum 12 in square or removable duct section) and be labeled externally as “FIRE/SMOKE DAMPER,” “SMOKE DAMPER” or “FIRE DAMPER.”
Worked example — concrete scenario
Scenario: A metal rectangular supply duct (no flexible connector) passes through a nonfire‑resistance‑rated concrete floor and the duct serves three consecutive stories (basement, first, second). You must determine protection.
- Is the floor assembly nonfire‑resistance‑rated? Yes — apply § 717.6.3.
- Does the duct connect not more than three stories? Yes — it connects three stories (basement→2nd). For floor assemblies composed of noncombustible materials, method 3 of § 717.6.3 applies: you may omit a shaft if (a) the annular space is protected with an approved noncombustible material that resists free passage of flame/products of combustion, and (b) a fire damper is installed at each floor line. So install a fire damper at the basement/first floor line and another at the first/second floor line, and seal the annular space appropriately.
- If the floor were combustible or you did not want to install fire dampers, the alternative would be to enclose the duct in a shaft enclosure complying with § 713.
Related provisions
- § 717.1.1 — Ducts transitioning horizontally between shafts; dampers allowed in lieu of shaft enclosure.
- § 717.6.2 — Requirements for horizontal assemblies and ceiling radiation/static damper rules (includes detector placement for static ceiling radiation dampers).
- § 717.6.3 — Protection methods for ducts penetrating nonfire‑resistance‑rated floor assemblies (the three alternative methods and the residential exception).
- § 717.3.3.2 — Smoke damper actuation requirements (detector locations and control methods).
- § 717.4.1 — Access requirements for fire and smoke dampers (inspection access and size).
- Section 714 (especially § 714.3–714.4) — Through‑penetration firestop systems and sleeve requirements for penetrations left without dampers.
If you need, I can produce:
- A one‑page checklist for plan reviewers/field installers listing the exact steps to verify compliance, or
- A diagram showing where dampers and detectors must be placed for common configurations.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 717.5.1 High relevance — show source text
717.5.1 Fire walls. Ducts and air transfer openings permitted in fire walls in accordance with Section 706.11 shall be protected with listed fire dampers installed in accordance with their listing.
717.5.1.1 Horizontal exits. A listed smoke damper designed to resist the passage of smoke shall be provided at each point a duct or air transfer opening penetrates a fire wall that serves as a horizontal exit.
717.5.2 Fire barriers. In other than Group A, E, H, I, L and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal. Ducts and air transfer openings of fire barriers shall be protected with listed fire dampers installed in accordance with their listing. Ducts and air transfer openings shall not penetrate enclosures for interior exit stairways and ramps and exit passageways, except as permitted by Sections 1023.5 and 1024.6, respectively.
Exceptions: Fire dampers are not required at penetrations of fire barriers where any of the following apply:
- Penetrations are tested in accordance with ASTM E119 or UL 263 as part of the fire-resistance-rated assembly.
- Ducts are used as part of an approved smoke control system in accordance with Section 909 and where the use of a fire damper would interfere with the operation of a smoke control system.
- Such walls are penetrated by fully ducted HVAC systems, have a required fire-resistance rating of 1 hour or less, are in areas of other than Group H and are in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2. For the purposes of this exception, a fully ducted HVAC system shall be a duct system for conveying supply, return or exhaust air as part of the structure’s HVAC system. Such a duct system shall be constructed of sheet steel not less than No. 26 gage thickness and shall be continuous from the air-handling appliance or equipment to the air outlet and inlet terminals. Nonmetal flexible air connectors shall be permitted in the following locations in accordance with Section 603 of the California Mechanical Code: 3.1. At the duct connection to the air handling unit or equipment located within the mechanical room. 3.2. From an overhead metal duct to a ceiling diffuser within the same room.
[SFM] For Group A, E, H, I, L and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, ducts and air transfer openings of fire barriers shall be protected with approved fire and smoke dampers installed in accordance with their listing. Ducts and air transfer openings shall not penetrate exit enclosures and exit passageways except as permitted by Sections 1023.5 and 1024.6, respectively.
Exceptions: 1. Fire dampers are not required at penetrations of fire barriers where penetrations are tested in accordance with ASTM E119 as part of the fire-resistance rated assembly.
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CMC § 3.1. High relevance — show source text
For the purposes of this exception, a fully ducted HVAC system shall be a duct system for conveying supply, return or exhaust air as part of the structure’s HVAC system. Such a duct system shall be constructed of sheet steel not less than No. 26 gage thickness and shall be continuous from the air-handling appliance or equipment to the air outlet and inlet terminals. Nonmetal flexible air connectors shall be permitted in the following locations in accordance with Section 603 of the California Mechanical Code: 3.1. At the duct connection to the air handling unit or equipment located within the mechanical room. 3.2. From an overhead metal duct to a ceiling diffuser within the same room.
[SFM] For Group A, E, H, I, L and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, ducts and air transfer openings of fire barriers shall be protected with approved fire and smoke dampers installed in accordance with their listing. Ducts and air transfer openings shall not penetrate exit enclosures and exit passageways except as permitted by Sections 1023.5 and 1024.6, respectively.
Exceptions: 1. Fire dampers are not required at penetrations of fire barriers where penetrations are tested in accordance with ASTM E119 as part of the fire-resistance rated assembly.
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2. Fire and smoke dampers are not required where ducts are used as part of an approved smoke control system in accordance with Section 909 and where the use of a fire or smoke damper would interfere with the operation of a smoke control system.
717.5.2.1 Horizontal exits. A listed smoke damper designed to resist the passage of smoke shall be provided at each point a duct or air transfer opening penetrates a fire barrier that serves as a horizontal exit.
717.5.3 Shaft enclosures. Shaft enclosures that are permitted to be penetrated by ducts and air transfer openings shall be protected with listed fire and smoke dampers installed in accordance with their listing.
Exceptions:
- Fire dampers are not required at penetrations of shafts where any of the following criteria are met: 1.1. Steel exhaust subducts having a wall thickness of not less than 0.0187 inch (0.4712 mm) are extended not less than 22 inches (559 mm) vertically in exhaust shafts, and an exhaust fan is installed at the upper terminus of the shaft that is powered continuously in accordance with Section 909.11, so as to maintain a continuous upward airflow to the outdoors. 1.2. Penetrations are tested in accordance with ASTM E119 or UL 263 as part of the fire-resistance-rated assembly. 1.3. Ducts are used as part of an approved smoke control system designed and installed in accordance with Section 909 and where the fire damper will interfere with the operation of the smoke control system. 1.4. The penetrations are in parking garage exhaust or supply shafts that are separated from other building shafts by not less than 2-hour fire-resistance-rated construction.
CMC § 1.4. High relevance — show source text
1.4. The penetrations are in parking garage exhaust or supply shafts that are separated from other building shafts by not less than 2-hour fire-resistance-rated construction. 2. In Group B and R occupancies equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1, smoke dampers are not required at penetrations of shafts where all of the following criteria are met: 2.1. Kitchen, clothes dryer, bathroom and toilet room exhaust openings are installed with steel exhaust subducts, having a wall thickness of not less than 0.0187 inch (0.4712 mm). 2.2. The subducts extend not less than 22 inches (559 mm) vertically. 2.3. An exhaust fan is installed at the upper terminus of the shaft that is powered continuously in accordance with the provisions of Section 909.11, so as to maintain a continuous upward airflow to the outdoors. 3. Smoke dampers are not required at penetration of exhaust or supply shafts in parking garages that are separated from other building shafts by not less than 2-hour fire-resistance-rated construction. 4. Smoke dampers are not required at penetrations of shafts where ducts are used as part of an approved mechanical smoke control system designed in accordance with Section 909 and where the smoke damper will interfere with the operation of the smoke control system. 5. Fire dampers and combination fire/smoke dampers are not required in kitchen and clothes dryer exhaust systems where dampers are prohibited by the California Mechanical Code .
717.5.3.1 Continuous upward airflow. Fire dampers and smoke dampers shall not be installed in shafts that are required to maintain a continuous upward airflow path where closure of the damper would result in the loss of the airflow.
717.5.4 Fire partitions. In other than Group A, E, I and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, ducts and air transfer openings that penetrate fire partitions shall be protected with listed fire dampers installed in accordance with their listing.
Exceptions: In occupancies other than Group H and L, fire dampers are not required where any of the following apply:
- Corridor walls in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2 and the duct is protected as a through penetration in accordance with Section 714.
- Tenant partitions in covered and open mall buildings where the walls are not required by provisions elsewhere in the code to extend to the underside of the floor or roof sheathing, slab or deck above.
- The duct system is constructed of approved materials in accordance with the California Mechanical Code and the duct penetrating the wall complies with all of the following requirements: 3.1. The duct shall not exceed 100 square inches (0.06 m [2] ). 3.2. The duct shall be constructed of steel not less than 0.0217 inch (0.55 mm) in thickness.
3.3. The duct shall not have openings that communicate the corridor with adjacent spaces or rooms. 3.4. The duct shall be installed above a ceiling. 3.5. The duct shall not terminate at a wall register in the fire-resistance-rated wall. 3.6. A minimum 12-inch-long (305 mm) by 0.060-inch-thick (1.52 mm) steel sleeve shall be centered in each duct opening.
CMC § 0.019 High relevance — show source text
Exceptions:
- Smoke dampers are not required where the building is equipped throughout with an approved smoke control system in accordance with Section 909, and smoke dampers are not necessary for the operation and control of the system.
- Smoke dampers are not required in corridor penetrations where the duct is constructed of steel not less than 0.019 inch (0.48 mm) in thickness and there are no openings serving the corridor.
[SFM] For Group A, E, H, I, L and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, a listed smoke damper designed to resist the passage of smoke shall also be provided at each point a duct or air transfer opening penetrates a fire-resistance rated corridor enclosure required to have smoke and draft doors in accordance with Section 716.2.2.1 or doors that provide an effective barrier to limit the transfer of smoke in accordance with Section 407.3.1.
Exceptions: 1. Smoke dampers are not required where ducts are used as part of an approved mechanical smoke control system designed in accordance with Section 909 and where the smoke damper will interfere with the operation of the smoke control system. 2. Smoke dampers are not required in corridor penetrations where the duct is constructed of steel not less than 0.019 inch (0.48 mm) in thickness and there are no openings serving the corridor. 717.5.5 Smoke barriers. A listed smoke damper designed to resist the passage of smoke shall be provided at each point a duct or air transfer opening penetrates a smoke barrier. Smoke dampers and smoke damper actuation methods shall comply with Section 717.3.3.2.
Exception: Smoke dampers are not required where the openings in ducts are limited to a single smoke compartment and the ducts are constructed of steel. � 717.5.6 Exterior walls. Ducts and air transfer openings in fire-resistance-rated exterior walls required to have protected openings in accordance with Section 705.11 shall be protected with listed fire dampers installed in accordance with their listing.
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717.5.7 Smoke partitions. A listed smoke damper designed to resist the passage of smoke shall be provided at each point that an air transfer opening penetrates a smoke partition. Smoke dampers and smoke damper actuation methods shall comply with Section 717.3.3.2.
Exception: Where the installation of a smoke damper will interfere with the operation of a required smoke control system in accordance with Section 909, approved alternative protection shall be utilized.
717.6 Horizontal assemblies. Penetrations by ducts and air transfer openings of a floor, floor/ceiling assembly or the ceiling membrane of a roof/ceiling assembly shall be protected by a shaft enclosure that complies with Section 713 or shall comply with Sections 717.6.1 through 717.6.3.
CMC § 509.1. High relevance — show source text
Waste chutes shall not terminate in an incinerator room. Waste and linen rooms that are not provided with chutes need only comply with Table 509.1.
713.13.5 Incinerator room. Incinerator rooms shall comply with Table 509.1.
713.13.6 Automatic sprinkler system. An approved automatic sprinkler system shall be installed in accordance with Section 903.2.11.2.
713.14 Elevator, dumbwaiter and other hoistways. A hoistway for elevators, dumbwaiters and other vertical devices shall comply with Section 712. Where the hoistway is required to be enclosed, it shall be constructed as a shaft enclosure in accordance with Section 713 and Chapter 30.
SECTION 714—PENETRATIONS
714.1 Scope. The provisions of this section shall govern the materials and methods of construction used to protect through penetrations and membrane penetrations of horizontal assemblies and fire-resistance-rated wall assemblies.
714.1.1 Ducts and air transfer openings. Penetrations of fire-resistance-rated walls by ducts that are not protected with dampers shall comply with Sections 714.3 through 714.4.3. Penetrations of horizontal assemblies not protected with a shaft as permitted by Section 717.6, and not required to be protected with fire dampers by other sections of this code, shall comply with Sections 714.5 through 714.6.2. Ducts and air transfer openings that are protected with dampers shall comply with Section 717.
714.2 Installation. A listed penetration firestop system shall be installed in accordance with the manufacturer’s installation instructions and the listing criteria.
714.3 Sleeves. Where sleeves are used, they shall be securely fastened to the assembly penetrated and installed in accordance with the sleeve manufacturer’s installation instructions. Where listed systems are used, the sleeve shall be installed in accordance with the listing criteria for the system. The space between the item contained in the sleeve and the sleeve itself and any space between the sleeve and the assembly penetrated shall be protected in accordance with this section. Insulation and coverings on or in the penetrating item shall not penetrate the assembly unless the specific material used has been tested as part of the assembly in accordance with this section.
714.4 Fire-resistance-rated walls. Penetrations into or through fire walls, fire barriers, smoke barrier walls and fire partitions shall comply with Sections 714.4.1 through 714.4.3. Penetrations in smoke barrier walls shall also comply with Section 714.5.4.
714.4.1 Through penetrations. Through penetrations of fire-resistance-rated walls shall comply with Section 714.4.1.1 or 714.4.1.2.
Exception: Where the penetrating items are steel, ferrous or copper pipes, tubes or conduits, the annular space between the penetrating item and the fire-resistance-rated wall is permitted to be protected by either of the following measures:
- In concrete or masonry walls where the penetrating item is a maximum 6-inch (152 mm) nominal diameter and the area of the opening through the wall does not exceed 144 square inches (0.0929 m [2] ), concrete, grout or mortar is permitted where installed the full thickness of the wall or the thickness required to maintain the fire-resistance rating.
CMC § 717.6.2.1.2 High relevance — show source text
717.6.2.1.2 Static systems. Static ceiling radiation dampers shall be provided with systems that are not designed to operate during a fire.
Exceptions:
- Where a static ceiling radiation damper is installed at the opening of a duct, a smoke detector shall be installed inside the duct or outside the duct with sampling tubes protruding into the duct. The detector or tubes in the duct shall be within 5 feet (1524 mm) of the damper. Air outlets and inlets shall not be located between the detector or tubes and the damper. The detector shall be listed for the air velocity, temperature and humidity
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anticipated at the point where it is installed. Other than in mechanical smoke control systems, dampers shall be closed upon fan shutdown where local smoke detectors require a minimum velocity to operate. 2. Where a static ceiling radiation damper is installed in a ceiling, the ceiling radiation damper shall be permitted to be controlled by a smoke detection system installed in the same room or area as the ceiling radiation damper. 3. A static ceiling radiation damper shall be permitted to be installed in a room where an occupant sensor is provided within the room that will shut down the system.
717.6.3 Nonfire-resistance-rated floor assemblies. Duct systems constructed of approved materials in accordance with the California Mechanical Code that penetrate nonfire-resistance-rated floor assemblies shall be protected by any of the following methods:
A shaft enclosure in accordance with Section 713.
The duct connects not more than two stories, and the annular space around the penetrating duct is protected with an approved noncombustible material that resists the free passage of flame and the products of combustion.
In floor assemblies composed of noncombustible materials, a shaft shall not be required where the duct connects not more than three stories, the annular space around the penetrating duct is protected with an approved noncombustible material that resists the free passage of flame and the products of combustion and a fire damper is installed at each floor line. Exception: Fire dampers are not required in ducts within individual residential dwelling units.
717.7 Flexible ducts and air connectors. Flexible ducts and air connectors shall not pass through any fire-resistance-rated assembly. Flexible air connectors shall not pass through any wall, floor or ceiling.
SECTION 718—CONCEALED SPACES
718.1 General. Fireblocking and draftstops shall be installed in combustible concealed locations in accordance with this section. Fireblocking shall comply with Section 718.2. Draftstops in floor/ceiling spaces and attic spaces shall comply with Sections 718.3 and 718.4, respectively. The permitted use of combustible materials in concealed spaces of buildings of Type I or II construction shall be limited to the applications indicated in Section 718.5.
718.2 Fireblocking. In combustible construction, fireblocking shall be installed to cut off concealed draft openings (both vertical and horizontal) and shall form an effective barrier between floors, between a top story and a roof or attic space. Fireblocking shall be installed in the locations specified in Sections 718.2.2 through 718.2.7.
CMC § 717.3.3.5 High relevance — show source text
717.3.3.5 Corridor damper actuation. Corridor damper actuation shall be in accordance with Sections 717.3.3.1 and 717.3.3.2.
717.4 Access and identification. Access and identification of fire and smoke dampers shall comply with Sections 717.4.1 through 717.4.2.
717.4.1 Access. Fire and smoke dampers shall be provided with an approved means of access that is large enough to permit inspection and maintenance of the damper and its operating parts. Dampers equipped with fusible links, internal operators, or both shall be provided with an access door that is not less than 12 inches (305 mm) square or provided with a removable duct section.
717.4.1.1 Access openings. The access shall not affect the integrity of fire-resistance-rated assemblies. The access openings shall not reduce the fire-resistance rating of the assembly. Access doors in ducts shall be tight fitting and suitable for the required duct construction.
717.4.1.2 Restricted access. Where space constraints or physical barriers restrict access to a damper for periodic inspection and testing, the damper shall be a single- or multi-blade type damper and shall comply with the remote inspection requirements of NFPA 80 or NFPA 105.
717.4.2 Identification. Access points shall be permanently identified on the exterior by a label having letters not less than [1] / 2 inch (12.7 mm) in height reading: “FIRE/SMOKE DAMPER,” “SMOKE DAMPER” or “FIRE DAMPER.”
717.5 Where required. Fire dampers, smoke dampers, combination fire/smoke dampers, ceiling radiation dampers and corridor dampers shall be provided at the locations prescribed in Sections 717.5.1 through 717.5.7 and 717.6. Where an assembly is required to have both fire dampers and smoke dampers, combination fire/smoke dampers or a fire damper and a smoke damper shall be provided.
717.5.1 Fire walls. Ducts and air transfer openings permitted in fire walls in accordance with Section 706.11 shall be protected with listed fire dampers installed in accordance with their listing.
717.5.1.1 Horizontal exits. A listed smoke damper designed to resist the passage of smoke shall be provided at each point a duct or air transfer opening penetrates a fire wall that serves as a horizontal exit.
717.5.2 Fire barriers. In other than Group A, E, H, I, L and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal. Ducts and air transfer openings of fire barriers shall be protected with listed fire dampers installed in accordance with their listing. Ducts and air transfer openings shall not penetrate enclosures for interior exit stairways and ramps and exit passageways, except as permitted by Sections 1023.5 and 1024.6, respectively.
Exceptions: Fire dampers are not required at penetrations of fire barriers where any of the following apply:
- Penetrations are tested in accordance with ASTM E119 or UL 263 as part of the fire-resistance-rated assembly.
- Ducts are used as part of an approved smoke control system in accordance with Section 909 and where the use of a fire damper would interfere with the operation of a smoke control system.
CMC § 717.1.1 High relevance — show source text
717.1.1 Ducts and air transfer openings. Ducts transitioning horizontally between shafts shall not require a shaft enclosure provided that the duct penetration into each associated shaft is protected with dampers complying with this section.
717.1.2 Ducts that penetrate fire-resistance-rated assemblies without dampers. Ducts that penetrate fire-resistance-rated walls and are not required by this section to have fire dampers shall comply with the requirements of Sections 714.3 through 714.4.3. Ducts that penetrate horizontal assemblies not required to be contained within a shaft and not required by this section to have fire dampers shall comply with the requirements of Sections 714.5 through 714.6.2.
717.1.2.1 Ducts that penetrate nonfire-resistance-rated assemblies. The space around a duct penetrating a nonfire-resistance-rated floor assembly shall comply with Section 717.6.3.
717.2 Installation. Fire dampers, smoke dampers, combination fire/smoke dampers and ceiling radiation dampers located within air distribution and smoke control systems shall be installed in accordance with the manufacturer’s instructions, the dampers’ listing and Sections 717.2.1 through 717.2.4.
717.2.1 Smoke control system. Where the installation of a fire damper will interfere with the operation of a required smoke control system in accordance with Section 909, approved alternative protection shall be utilized. Where mechanical systems including ducts and dampers utilized for normal building ventilation serve as part of the smoke control system, the expected performance of these systems in smoke control mode shall be addressed in the rational analysis required by Section 909.4.
717.2.2 Hazardous exhaust ducts. Fire dampers for hazardous exhaust duct systems shall comply with the California Mechanical Code .
717.2.3 Static dampers. Fire dampers and ceiling radiation dampers that are listed for use in static systems shall only be installed in heating, ventilation and air-conditioning systems that are automatically shut down in the event of a fire.
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717.2.4 Mechanical, electrical and plumbing controls. Mechanical, electrical and plumbing controls shall not be installed in air duct systems.
Exception: Controls where the wiring is directly associated with the air distribution system. The wiring shall comply with the requirements of Section 601 of the California Mechanical Code and be as short as practicable.
717.2.4.1 Controls not permitted to be installed through dampers. Mechanical, electrical and plumbing controls shall not be installed through fire dampers, smoke dampers, combination fire/smoke dampers or ceiling radiation dampers unless otherwise permitted by the manufacturer and the listing.
717.3 Damper testing, ratings and actuation. Damper testing, ratings and actuation shall be in accordance with Sections 717.3.1 through 717.3.3.
717.3.1 Damper testing. Dampers shall be listed and labeled in accordance with the standards in this section.
- Fire dampers shall comply with the requirements of UL 555.
- Smoke dampers shall comply with the requirements of UL 555S.
- Combination fire/smoke dampers shall comply with the requirements of both UL 555 and UL 555S.
CMC § 717.5.2.1 High relevance — show source text
2. Fire and smoke dampers are not required where ducts are used as part of an approved smoke control system in accordance with Section 909 and where the use of a fire or smoke damper would interfere with the operation of a smoke control system.
717.5.2.1 Horizontal exits. A listed smoke damper designed to resist the passage of smoke shall be provided at each point a duct or air transfer opening penetrates a fire barrier that serves as a horizontal exit.
717.5.3 Shaft enclosures. Shaft enclosures that are permitted to be penetrated by ducts and air transfer openings shall be protected with listed fire and smoke dampers installed in accordance with their listing.
Exceptions:
- Fire dampers are not required at penetrations of shafts where any of the following criteria are met: 1.1. Steel exhaust subducts having a wall thickness of not less than 0.0187 inch (0.4712 mm) are extended not less than 22 inches (559 mm) vertically in exhaust shafts, and an exhaust fan is installed at the upper terminus of the shaft that is powered continuously in accordance with Section 909.11, so as to maintain a continuous upward airflow to the outdoors. 1.2. Penetrations are tested in accordance with ASTM E119 or UL 263 as part of the fire-resistance-rated assembly. 1.3. Ducts are used as part of an approved smoke control system designed and installed in accordance with Section 909 and where the fire damper will interfere with the operation of the smoke control system. 1.4. The penetrations are in parking garage exhaust or supply shafts that are separated from other building shafts by not less than 2-hour fire-resistance-rated construction.
- In Group B and R occupancies equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1, smoke dampers are not required at penetrations of shafts where all of the following criteria are met: 2.1. Kitchen, clothes dryer, bathroom and toilet room exhaust openings are installed with steel exhaust subducts, having a wall thickness of not less than 0.0187 inch (0.4712 mm). 2.2. The subducts extend not less than 22 inches (559 mm) vertically. 2.3. An exhaust fan is installed at the upper terminus of the shaft that is powered continuously in accordance with the provisions of Section 909.11, so as to maintain a continuous upward airflow to the outdoors.
- Smoke dampers are not required at penetration of exhaust or supply shafts in parking garages that are separated from other building shafts by not less than 2-hour fire-resistance-rated construction.
- Smoke dampers are not required at penetrations of shafts where ducts are used as part of an approved mechanical smoke control system designed in accordance with Section 909 and where the smoke damper will interfere with the operation of the smoke control system.
- Fire dampers and combination fire/smoke dampers are not required in kitchen and clothes dryer exhaust systems where dampers are prohibited by the California Mechanical Code .
717.5.3.1 Continuous upward airflow. Fire dampers and smoke dampers shall not be installed in shafts that are required to maintain a continuous upward airflow path where closure of the damper would result in the loss of the airflow.
CMC § 0.060 High relevance — show source text
2. The sleeve shall be secured to both sides of the wall and for all four sides of the sleeve with minimum 1 [1] / 2 -inch by 1 [1] / 2 -inch by 0.060-inch (38 mm by 38 mm by 1.52 mm) steel retaining angles. 3. The retaining angles shall be secured to the sleeve and the wall with No. 10 (M5) screws. 4. The annular space between the steel sleeve and the wall opening shall be filled with mineral wool batting on all sides.
717.5.4.1 Corridors. In other than Group A, E, H, I, L and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, duct and air transfer openings that penetrate corridors shall be protected with dampers as follows:
- A corridor damper shall be provided where corridor ceilings, constructed as required for the corridor walls as permitted in Section 708.4, Exception 3, are penetrated.
- A ceiling radiation damper shall be provided where the ceiling membrane of a fire-resistance-rated floor-ceiling or roof-ceiling assembly, constructed as permitted in Section 708.4, Exception 2, is penetrated.
- A listed smoke damper designed to resist the passage of smoke shall be provided at each point a duct or air transfer opening penetrates a corridor enclosure required to have smoke and draft control doors in accordance with Section 716.2.2.1.
Exceptions:
- Smoke dampers are not required where the building is equipped throughout with an approved smoke control system in accordance with Section 909, and smoke dampers are not necessary for the operation and control of the system.
- Smoke dampers are not required in corridor penetrations where the duct is constructed of steel not less than 0.019 inch (0.48 mm) in thickness and there are no openings serving the corridor.
[SFM] For Group A, E, H, I, L and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, a listed smoke damper designed to resist the passage of smoke shall also be provided at each point a duct or air transfer opening penetrates a fire-resistance rated corridor enclosure required to have smoke and draft doors in accordance with Section 716.2.2.1 or doors that provide an effective barrier to limit the transfer of smoke in accordance with Section 407.3.1.
Exceptions: 1. Smoke dampers are not required where ducts are used as part of an approved mechanical smoke control system designed in accordance with Section 909 and where the smoke damper will interfere with the operation of the smoke control system. 2. Smoke dampers are not required in corridor penetrations where the duct is constructed of steel not less than 0.019 inch (0.48 mm) in thickness and there are no openings serving the corridor. 717.5.5 Smoke barriers. A listed smoke damper designed to resist the passage of smoke shall be provided at each point a duct or air transfer opening penetrates a smoke barrier. Smoke dampers and smoke damper actuation methods shall comply with Section 717.3.3.2.
CMC § 714.3 High relevance — show source text
714.3 Sleeves. Where sleeves are used, they shall be securely fastened to the assembly penetrated and installed in accordance with the sleeve manufacturer’s installation instructions. Where listed systems are used, the sleeve shall be installed in accordance with the listing criteria for the system. The space between the item contained in the sleeve and the sleeve itself and any space between the sleeve and the assembly penetrated shall be protected in accordance with this section. Insulation and coverings on or in the penetrating item shall not penetrate the assembly unless the specific material used has been tested as part of the assembly in accordance with this section.
714.4 Fire-resistance-rated walls. Penetrations into or through fire walls, fire barriers, smoke barrier walls and fire partitions shall comply with Sections 714.4.1 through 714.4.3. Penetrations in smoke barrier walls shall also comply with Section 714.5.4.
714.4.1 Through penetrations. Through penetrations of fire-resistance-rated walls shall comply with Section 714.4.1.1 or 714.4.1.2.
Exception: Where the penetrating items are steel, ferrous or copper pipes, tubes or conduits, the annular space between the penetrating item and the fire-resistance-rated wall is permitted to be protected by either of the following measures:
- In concrete or masonry walls where the penetrating item is a maximum 6-inch (152 mm) nominal diameter and the area of the opening through the wall does not exceed 144 square inches (0.0929 m [2] ), concrete, grout or mortar is permitted where installed the full thickness of the wall or the thickness required to maintain the fire-resistance rating.
- The material used to fill the annular space shall prevent the passage of flame and hot gases sufficient to ignite cotton waste when subjected to ASTM E119 or UL 263 time-temperature fire conditions under a minimum positive pressure
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FIRE AND SMOKE PROTECTION FEATURES
differential of 0.01 inch of water (2.49 Pa) at the location of the penetration for the time period equivalent to the fireresistance rating of the construction penetrated.
714.4.1.1 Fire-resistance-rated assemblies. Through penetrations shall be protected using systems installed as tested in the approved fire-resistance-rated assembly.
714.4.1.2 Through-penetration firestop system. Through penetrations shall be protected by an approved penetration firestop system installed as tested in accordance with ASTM E814 or UL 1479, with a minimum positive pressure differential of 0.01 inch of water (2.49 Pa) and shall have an F rating of not less than the required fire-resistance rating of the wall penetrated.
714.4.2 Membrane penetrations. Membrane penetrations shall comply with Section 714.4.1. Where walls or partitions are required to have a fire-resistance rating, recessed fixtures shall be installed such that the required fire resistance will not be reduced.
Exceptions: 1.
CMC § 712.1.5.2 High relevance — show source text
712.1.5.2 Joints in or between nonfire-resistance-rated floor assemblies. Joints in or between floor assemblies without a required fire-resistance rating shall be permitted where they comply with one of the following:
- The joint shall be concealed within the cavity of a wall.
- The joint shall be located above a ceiling.
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- The joint shall be sealed, treated or covered with an approved material or system to resist the free passage of flame and the products of combustion.
Exception: Joints meeting one of the exceptions specified in Section 715.3.
712.1.6 Ducts and air transfer openings. Penetrations by ducts and air transfer openings shall be protected in accordance with Section 717. Grease ducts shall be protected in accordance with the California Mechanical Code.
712.1.7 Atriums. Atriums complying with Section 404 that connect two or more stories in Group I-2 or I-3 occupancies or three or more stories in other occupancies shall be permitted.
Exceptions:
- Atriums shall not be permitted within Group H occupancies.
- Balconies or stories within Groups A-1, A-4 and A-5 and mezzanines that comply with Section 505 shall not be considered a story as it applies to this section
712.1.8 Masonry chimney. Approved vertical openings for masonry chimneys shall be permitted where the annular space is fireblocked at each floor level in accordance with Section 718.2.5.
712.1.9 Two-story openings. In other than Groups I-2 and I-3, a vertical opening that is not used as one of the applications specified in this section shall be permitted if the opening complies with all of the following items:
Does not connect more than two stories.
Does not penetrate a horizontal assembly that separates fire areas or smoke barriers that separate smoke compartments.
Is not concealed within the construction of a wall or a floor/ceiling assembly.
Is not open to a corridor in Group I and R occupancies.
Is not open to a corridor on nonsprinklered floors.
Is separated from floor openings and air transfer openings serving other floors by construction conforming to required shaft enclosures.
712.1.10 Parking garages. Vertical openings in parking garages for automobile ramps, elevators and duct systems shall comply with Section 712.1.10.1, 712.1.10.2 or 712.1.10.3, as applicable.
712.1.10.1 Automobile ramps. Vertical openings for automobile ramps in parking garages shall be permitted where constructed in accordance with Sections 406.5 and 406.6.
712.1.10.2 Elevators. Vertical openings for elevator hoistways in parking garages that serve only the parking garage, and complying with Sections 406.5 and 406.6, respectively, shall be permitted.
712.1.10.3 Duct systems. Vertical openings for mechanical exhaust or supply duct systems in parking garages complying with Sections 406.5 and 406.6, respectively, shall be permitted to be unenclosed where such duct system is contained within and serves only the parking garage.
Frequently asked questions
What is the difference between a fire damper and a smoke damper?
A fire damper prevents passage of flame and hot gases through a penetration during fire; a smoke damper prevents the movement of smoke. When both functions are required, provide a combination fire/smoke damper or both devices.
When can I avoid installing a damper at a wall penetration?
If the wall penetration is part of an assembly tested as a whole (ASTM E119 / UL‑263) or the ducts are part of an approved smoke control system where a damper would interfere with operation, then a damper may not be required. Check the specific exceptions in the code.
Can flexible ducts pass through fire‑resistance‑rated assemblies?
No. Flexible ducts and air connectors shall not pass through any fire‑resistance‑rated assembly. Flexible air connectors shall not pass through any wall, floor or ceiling.
How close must a smoke detector be to a damper in a duct?
A detector (or sampling tube) must be within 5 feet (1524 mm) of the smoke damper when the damper is inside a duct.
Are fire dampers required inside individual dwelling units?
No — the code exempts fire dampers in ducts located entirely within an individual residential dwelling unit.
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