Damper Guide

Damper types

Fire dampers: where the IBC requires them and what to specify

A fire damper closes automatically when its heat-responsive device, usually a fusible link, reaches its operating temperature. It keeps fire from passing through ducts and air transfer openings in fire-resistance-rated walls and floors.

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
Rating
At least 1-1/2 hours in assemblies rated less than 3 hours, and 3 hours in assemblies rated 3 hours or more.
Closes on
Heat only. The operating temperature is about 50°F above the normal duct temperature and at least 160°F, or no more than 350°F in a smoke control system.

IBC 717.3.1, Table 717.3.2.1, 717.3.3.1

Where the IBC requires a fire damper

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

What to specify

2018 IBC only

  • Listed to UL 555
  • 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
  • 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

IBC 717.3.1, IBC 717.3.2.1, IBC 717.3.3.1, IBC 717.3.1 item 1

2021 and 2024 IBC

  • Listed to UL 555
  • 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
  • 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

IBC 717.3.1, IBC 717.3.2.1, IBC 717.3.3.1, IBC 717.2.3

Fire damper vs combination fire/smoke damper

A fire damper responds to heat and is rated for fire resistance only. It is not tested for smoke leakage. Where the same opening also needs a smoke damper, use a combination fire/smoke damper, or a fire damper plus a separate smoke damper. More about the combination fire/smoke damper.

Static or dynamic

Since 2021, fire dampers listed for static systems may go only in HVAC systems that shut down automatically in a fire. The 2018 IBC instead required a dynamic label where the fans run during a fire. "Dynamic" is a closure rating from the UL 555 listing; the IBC does not define it. IBC 717.2.3 (2021 and 2024), 717.3.1 item 1 (2018)

Smoke control systems

If a fire damper would interfere with a required smoke control system, approved alternative protection is used instead. IBC 717.2.1

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)
  • 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

Does a fire damper need a smoke detector?

No. A fire damper closes on heat. Smoke detection is needed only where a smoke damper or a combination fire/smoke damper is required.

Is a fire damper required in every 1-hour wall?

No. It depends on what the wall is. In a 1-hour fire barrier, for example, the fire damper can be dropped for fully ducted steel HVAC systems in sprinklered buildings.

Fire damper: not required2021 and 2024 IBC

Fire damper: not required. The fire barrier is rated 1 hour or less, the building is fully sprinklered, neither side is a Group H area, and the duct is a fully ducted steel HVAC system that is continuous from the equipment to the outlets. IBC 717.5.2 Exc. 3

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 required2018 IBC only

Fire damper: not required. The fire barrier is rated 1 hour or less, the building is fully sprinklered, neither side is a Group H area, and the duct is a ducted steel HVAC system that is continuous from the equipment to the outlets. IBC 717.5.2 Exc. 3

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

Can a fire damper at a floor be replaced by other protection?

For a duct connecting two stories through a rated floor, the duct may instead be protected as required by IBC 714.5 (2024; in 2018 and 2021 only outside Groups I-2 and I-3).

Fire damper: requiredAll three editions

Fire damper: required. A duct through a rated floor connecting only two stories may skip the shaft if a listed fire damper is placed at the floor line. Or protect the duct as required by IBC 714.5 instead of the damper. IBC 717.6.1

Full result in the tool: Fire damper at the floor line, or duct protection per IBC 714.5

Illustration