UL 10C Fire-Rated Door Assemblies

Testing, ratings, hardware, and inspection requirements for fire door assemblies

Last updated: March 22, 2026

Overview

UL 10C is the fire test standard for door assemblies. Its full title is "Positive Pressure Fire Tests of Door Assemblies." It replaced the older UL 10B standard by adding a positive pressure condition during the test, which better simulates real fire behavior.

In a real fire, the fire side of a wall is under positive pressure. Hot gases push outward through any gap they can find. The old UL 10B test used a neutral pressure furnace, which meant doors could pass the test even if they had gaps that would leak smoke and flame under real conditions. UL 10C applies positive pressure after the first 5 minutes of the test, forcing the door assembly to resist both heat and pressure for the full rated duration.

The International Building Code (IBC) Section 716.2 requires that fire door assemblies be tested per NFPA 252 or UL 10C. Most manufacturers now test to UL 10C because it is the more demanding standard and satisfies all code references.

Why it matters: A fire door that passed UL 10B but would fail UL 10C can leak smoke and flame at the gaps between the door and frame. That gap is exactly where people die in corridor fires. Positive pressure testing catches this failure mode.

Fire Protection Rating Durations

Fire doors carry a "fire protection rating" measured in minutes or hours. This is the duration the assembly survived in the UL 10C test. IBC Table 716.1 (Opening Fire Protection Assemblies) specifies which rating is required based on the wall type the door is installed in.

The general rule: the door rating is typically 75% of the wall rating. A 2-hour fire wall gets a 90-minute door. A 1-hour corridor wall gets a 20-minute or 45-minute door depending on the occupancy and sprinkler status.

Door Rating	Wall Rating	Where Required (IBC)
20 minutes	1-hour corridor wall (sprinklered building)	Corridors in most sprinklered occupancies
45 minutes	1-hour fire partition or corridor wall	Corridor doors in non-sprinklered buildings, dwelling/sleeping unit separations
60 minutes (1 hour)	1- or 2-hour fire barrier	Exit enclosure doors in buildings 4 stories or less, shaft enclosures
90 minutes (1.5 hours)	2-hour fire barrier or exit enclosure	Exit stairway doors in buildings over 4 stories, 2-hour fire barriers
3 hours	3- or 4-hour fire wall	Fire walls separating buildings or occupancies, party walls

Warning: Do not assume you can use a 20-minute door just because the building has sprinklers. The required rating depends on the wall type, not just the sprinkler status. A 2-hour exit enclosure wall in a sprinklered building still requires a 90-minute door per IBC Table 716.1.

Required Fire-Rated Hardware

A fire door is an assembly, not just a door leaf. Every piece of hardware on that door must be listed for use on fire-rated openings. If you replace one component with a non-rated part, the entire assembly loses its rating.

Door closer

Required on every fire door. The closer must be UL listed and must reliably close and latch the door from any open position. Self-closing is non-negotiable. A fire door propped open with a wedge is a fire door that does not work. See our ANSI A156.4 Door Closers guide for grade and specification details.

Latch and strike

Fire doors must positively latch. This means the latch bolt must fully engage the strike plate when the door closes. A door that swings shut but does not latch can be pushed open by fire pressure. Roller latches are not permitted on fire-rated openings because they do not resist positive pressure.

Hinges

Steel hinges (steel base material) are required. Hinges must be listed for fire-rated openings. Spring hinges can substitute for a door closer on some ratings, but this varies by listing. Most AHJs prefer a dedicated closer.

Exit devices (panic hardware)

When panic hardware is required on a fire door, it must be fire exit hardware, tested and labeled per both UL 305 (panic hardware) and UL 10C (fire test). Standard panic hardware is not permitted on fire-rated openings. See our IBC Panic Hardware page for full requirements.

Glazing (glass)

Glass in a fire door must be fire-rated glazing tested as part of the door assembly. Wired glass (traditional) and ceramic glass (newer) are both used. The glass area is limited based on the door rating: 100 sq in maximum for doors rated over 60 minutes unless the glazing carries its own hourly temperature-rise rating. IBC Section 716.2.6.1 covers the details.

Gasketing and edge seals

Intumescent seals expand when heated to close the gap between the door and frame. Many fire door listings require specific gasketing. If the listing calls for it, the gasket is part of the rated assembly and cannot be removed or substituted.

Electric Hardware on Fire Doors

Access control hardware on fire doors is common in commercial buildings. Electric strikes, electromagnetic locks, and electrified exit devices are all used. The key requirement: the hardware must not prevent the door from closing and latching during a fire.

Electric strikes

An electric strike replaces the standard strike plate and can be unlocked remotely. For fire doors, the strike must be fail-secure (locked when power is lost) so the door latches properly during a fire when power may be cut. Electric strikes on fire doors must be UL listed for fire-rated openings. ANSI/BHMA A156.31 covers the performance standard for electrified hardware on fire doors.

Electromagnetic locks (maglocks)

Maglocks hold the door closed with an electromagnet. They must be fail-safe (released when power is lost) for egress. On fire doors, maglocks must release on fire alarm signal so the door can close and latch via its closer. A maglock that holds a fire door open during a fire defeats the purpose of the fire door. IBC Section 1010.2.11 governs electromagnetic lock requirements.

Electrified exit devices

Fire exit hardware with built-in electric latch retraction or electric dogging. The device must fail to the latched and locked position during a fire alarm. Electric dogging (holding the pushbar in) is not permitted on fire-rated openings because it prevents positive latching.

Magnetic hold-open devices

Electromagnetic hold-open devices are the only code-compliant way to hold a fire door open. They connect to the fire alarm system and release the door when the alarm activates, allowing the closer to shut it. Wedges, kickstands, and rope are never acceptable. Hold-open devices must be UL listed and connected to the building fire alarm per NFPA 72.

Tip: When specifying electric hardware for fire doors, always confirm that the specific make and model is UL listed for the fire rating of the door. A product being "fire-rated" generically is not enough. The listing must cover the specific door rating and configuration.ANSI/BHMA A156.31 addresses electrified hardware performance on fire doors specifically.

NFPA 80 Inspection Requirements

NFPA 80 (Standard for Fire Doors and Other Opening Protectives) requires annual inspection of all fire door assemblies. This requirement was introduced in the 2007 edition. The current edition is 2025.

The inspection must verify that each fire door assembly is functional and maintained. NFPA 80 Section 5.2 lists the specific items that must be checked during each annual inspection.

Annual inspection checklist (NFPA 80 Section 5.2):

No open holes or breaks in surfaces of door or frame
Glazing, vision light frame, and glazing beads are intact
Door, frame, hinges, hardware, and noncombustible threshold are not missing or broken
No parts are missing or broken
Door closer is operational and closes the door fully from any open position
Door latches securely when closed (positive latching verified)
Coordinator (on pairs of doors) is working so doors close in the correct sequence
Door clearance at bottom is 3/4 inch or less (3/8 inch or less for smoke doors)
Self-closing device is not disabled or blocked
No field modifications that void the fire rating
Gasketing and edge seals are intact where required by the listing
Fire door labels are present and legible on door and frame

Warning: Propping a fire door open with a wedge, can, or other object is the single most common fire door violation. It defeats the self-closing function and is an automatic inspection failure. If a door needs to be held open, the only compliant method is an electromagnetic hold-open device connected to the fire alarm system.

Written records of each inspection must be maintained and made available to the authority having jurisdiction (AHJ). Records should document the door location, the items inspected, the result (pass/fail), and any corrective actions taken.

Labels and Certification Marks

Every fire-rated door and frame must carry a label from an accredited testing laboratory. The label is the proof that the assembly was tested and meets the required fire protection rating. A fire door without a legible label is treated as a non-rated door during inspection.

How to read a fire door label:

Testing laboratory mark

UL (Underwriters Laboratories), Intertek/WHI (Warnock Hersey), or QAI are the most common. The mark tells you which lab tested and listed the assembly.

Fire protection rating

Shown in minutes or hours (e.g., "90 MIN" or "3 HR"). This is the duration the assembly survived in the fire test.

Temperature rise rating

Some doors carry a temperature rise limit (e.g., "250F/30 MIN" means the unexposed face temperature does not rise more than 250 degrees F in the first 30 minutes). Required for exit enclosure doors and doors in exit passageways per IBC Section 716.2.6.4.

Maximum door size

The label may state the maximum single leaf size the listing covers. Oversized doors may require a separate listing.

"S" label (smoke and draft control)

An "S" on the label means the assembly also meets UL 1784 for air leakage (smoke control). Required when the door serves a smoke barrier or smoke partition per IBC Section 716.2.6.3.

Tip: Fire door labels are usually on the hinge edge of the door and on the head of the frame. If a label has been painted over, removed, or is illegible, the door fails inspection. Replacement labels can be obtained from the original manufacturer or through a field labeling service from UL, Intertek, or QAI. Field labeling requires an on-site inspection to verify the assembly meets the rating requirements.

Common Fire Door Violations

These are the violations that inspectors find most often. Each one means the fire door cannot perform its job of containing fire and smoke to one side of the wall.

Violation	Why It Fails	Fix
Door propped or wedged open	Self-closing function is defeated. Door will not close during a fire.	Remove the prop. If the door needs to stay open, install a magnetic hold-open device tied to the fire alarm.
Missing or broken closer	Door will not self-close. Fire spreads through the opening.	Replace with a UL listed closer appropriate for the door size and rating.
Door does not latch	Positive pressure from a fire pushes the door open if the latch does not engage the strike.	Adjust strike plate, repair latch mechanism, or replace lockset.
Excessive bottom gap	Gap over 3/4 inch allows fire and smoke to pass under the door.	Adjust door or install a listed door bottom seal. Do not cut the door to fit.
Missing or illegible label	No way to verify the door is fire-rated. Inspector must treat it as non-rated.	Contact manufacturer for replacement label or arrange for field labeling inspection.
Non-rated hardware installed	Any non-listed component voids the entire assembly rating. Common with replacement locksets and closers.	Replace with hardware listed for use on fire-rated openings.
Holes or damage in door leaf	Holes from removed hardware, kicks, or impacts breach the fire resistance of the door.	Patch with listed fire door repair compound or replace the door if damage is extensive.
Coordinator not functioning (pairs)	On double doors, the inactive leaf must close first. If the active leaf closes first, neither leaf latches properly.	Repair or replace the coordinator device.

Frequently Asked Questions

What is the difference between UL 10B and UL 10C?

UL 10B tested door assemblies at neutral pressure. UL 10C adds a positive pressure condition after the first 5 minutes, simulating the pressure that a real fire creates on the fire side of a wall. UL 10C is the more demanding test and has effectively replaced UL 10B for new fire door listings. IBC references both NFPA 252 and UL 10C as acceptable test methods.

How often must fire doors be inspected?

NFPA 80 requires annual inspection of all fire door assemblies. This requirement has been in effect since the 2007 edition. The inspection must verify that all components are functional and that the door closes and latches properly. Written records must be kept.

Can I replace hardware on a fire door with standard hardware?

No. Every component on a fire door must be listed for use on fire-rated openings. Replacing a fire-rated closer, lockset, or hinge with a standard product voids the assembly rating. Even small items like door viewers, kickplates, and signage must be approved for use on fire-rated doors per the door manufacturer or listing.

What happens if a fire door label is missing?

A fire door without a legible label cannot be verified as fire-rated. The AHJ may require the door to be replaced. Alternatively, a field labeling service from UL, Intertek/WHI, or QAI can inspect the door on-site and issue a replacement label if the assembly meets the requirements. Field labeling is typically less expensive than full door replacement.

Can I hold a fire door open with a doorstop or wedge?

No. Propping a fire door open with any object is a code violation. The only compliant method is an electromagnetic hold-open device connected to the building fire alarm system. When the alarm activates, the device releases and the closer shuts the door automatically.

Do electric strikes void the fire rating of a door?

Not if the electric strike is UL listed for fire-rated openings and is fail-secure (locks when power is lost). The door must still positively latch during a fire. Electric strikes that are fail-safe (unlock when power is lost) are generally not permitted on fire doors because the door would not latch during a power failure.