Damper types

Combination fire/smoke dampers: when you need one and what to specify

One assembly that meets both the fire damper and the smoke damper standards. Where an opening needs both, the code allows a combination damper or a separate fire damper and smoke damper.

Rules last reviewed October 12, 2026. How the rules are checked

Check which damper your penetration needs (2024 IBC)Start the tool with the 2021 IBC · Start the tool with the 2018 IBC

Standard, rating and actuation

Test standard: UL 555 and UL 555S
Rating: The fire damper rating from Table 717.3.2.1 plus the smoke damper leakage and temperature ratings.
Closes on: Closes on heat like a fire damper and on smoke detection like a smoke damper. In smoke control system shaft penetrations, local area smoke detection may be used only as a secondary signal after the smoke control system controls.

IBC 717.5, 717.3.2.3, 717.3.3.3

Where the IBC requires a combination fire/smoke damper

Where the IBC requires a combination fire/smoke damper, unless an exception applies (each page lists the exceptions):

Fire walls (IBC 717.5.1, 717.5.1.1): horizontal exits only
Fire barriers (IBC 717.5.2, 717.5.2.1): horizontal exits only
Shaft enclosures (IBC 717.5.3)
Rated corridors (IBC 717.5.4, 717.5.4.1): corridor walls
Smoke barriers (IBC 717.5.5, 717.6.1): smoke barrier floors only, ducts only

What to specify

2018 IBC only

Listed to UL 555 and UL 555S
Fire rating: 1-1/2 hours where the assembly is rated less than 3 hours, 3 hours where it is rated 3 hours or more
Leakage rating: Class I or Class II
Elevated temperature rating: at least 250°F
Closes on activation of listed smoke detection as described in IBC 717.3.3.2
Heat-responsive device set about 50°F above normal duct temperature and at least 160°F, or, in a smoke control system, at no more than 350°F
If the HVAC fans run during a fire, the fire damper must be labeled for dynamic systems (the fire damper rule, applied to the fire damper part)

IBC 717.3.1, IBC 717.3.2.3, IBC 717.3.3.3, IBC 717.3.1 item 1

2021 and 2024 IBC

Listed to UL 555 and UL 555S
Fire rating: 1-1/2 hours where the assembly is rated less than 3 hours, 3 hours where it is rated 3 hours or more
Leakage rating: Class I or Class II
Elevated temperature rating: at least 250°F
Closes on activation of listed smoke detection as described in IBC 717.3.3.2
Heat-responsive device set about 50°F above normal duct temperature and at least 160°F, or, in a smoke control system, at no more than 350°F
Dampers listed for static systems only in HVAC systems that shut down automatically in a fire (the fire damper rule, applied to the fire damper part)

IBC 717.3.1, IBC 717.3.2.3, IBC 717.3.3.3, IBC 717.2.3

Combination fire/smoke damper vs fire damper

A combination fire/smoke damper adds smoke detection, an actuator and a leakage rating to a fire damper. It is needed only where a rule requires both a fire damper and a smoke damper at the same opening, most often at shaft penetrations and horizontal exits. More about the fire damper.

Installation basics

Access. Fire and smoke dampers need access large enough to inspect and maintain the damper. Since 2021, dampers with fusible links or internal operators need an access door at least 12 inches square or a removable duct section. IBC 717.4 (2018), 717.4.1 (2021 and 2024)
Labels. Mark each access point with letters at least 1/2 inch high reading FIRE DAMPER, SMOKE DAMPER or FIRE/SMOKE DAMPER. IBC 717.4.2 (717.4 in 2018)
Static versus dynamic. Since 2021, fire dampers and ceiling radiation dampers listed for static systems may be used only in HVAC systems that shut down automatically in a fire. For ceiling radiation dampers, the exceptions in IBC 717.6.2.1.2 also allow static dampers with certain smoke detector or occupant sensor controls. IBC 717.2.3, 717.6.2.1.2 (2021 and 2024)
Restricted access (2021 and 2024). Where access for periodic inspection and testing is restricted, use a single- or multi-blade damper that meets the remote inspection requirements of NFPA 80 (fire dampers) or NFPA 105 (smoke dampers). IBC 717.4.1.2

Rules for every damper type (installing to the listing, no flexible ducts through rated assemblies, no controls through dampers in 2024) are on the damper types page.

Questions

Can I use a fire damper and a separate smoke damper instead?

Yes. Where both are required, the code allows either a combination damper or one of each.

Fire damper: required · Smoke damper: requiredAll three editions

Fire damper: required. Shaft enclosure penetrations need fire and smoke dampers, and no fire damper exception applies. IBC 717.5.3

Smoke damper: required. Shaft enclosure penetrations need fire and smoke dampers, and no smoke damper exception applies. IBC 717.5.3

Full result in the tool: Combination fire/smoke damper required

Does every shaft penetration need a combination damper?

No. Several exceptions remove the fire damper, the smoke damper or both.

Fire damper: not required · Smoke damper: not required2021 and 2024 IBC

Fire damper: not required. The exhaust connection has a steel subduct at least 0.0187 inch thick extending 22 inches up the shaft, with a continuously powered exhaust fan at the top of the shaft. IBC 717.5.3 Exc. 1.1

Smoke damper: not required. In a Group B or R building with NFPA 13 sprinklers, kitchen, clothes dryer, bathroom or toilet room exhaust with 26 gage steel subducts extending 22 inches up the shaft and a continuously powered exhaust fan at the top does not need smoke dampers. IBC 717.5.3 Exc. 2

Also: Where no damper is required, the duct penetration must still be firestopped so the wall keeps its rating (through-penetration or membrane-penetration protection). IBC 717.1.2, IBC 714.3 to 714.4.3

Full result in the tool: No damper required

Fire damper: not required · Smoke damper: not required2018 IBC only

Fire damper: not required. The exhaust connection has a steel subduct extending 22 inches up the shaft with continuous upward airflow to the outside. IBC 717.5.3 Exc. 1.1