A common question is why the rating of the fire door assembly (e.g. 20 minutes) is less than the rating of the wall (e.g. half-an-hour or one hour). For most applications, the fire door assembly is tested for a shorter period than the wall because of the increased fuel load likely to be present adjacent to the wall. A swinging fire door would be unaffected by furniture or stored items that might impact the wall’s performance. If a fire door is no longer in use and it is not required for egress, NFPA 80-2016 requires the opening to be filled to maintain the rating of the wall assembly.
Although smoke control is the main concern in locations where 20-minute assemblies are required, 20-minute doors are classified as fire doors, not smoke doors. Fire-protection-rated assemblies are tested to Underwriters Laboratories (UL) 10C, Standard for Positive Pressure Fire Tests of Door Assemblies, or NFPA 252, Standard Methods of Fire Tests of Door Assemblies. Fire-resistance-rated assemblies are tested to ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials, or UL 263, Standard for Fire Tests of Building Construction and Materials. Smoke doors are not tested to these standards.
Smoke infiltration
UL 1784, Standard for Air Leakage Tests of Door Assemblies and Other Opening Protectives, applies to some fire doors and smoke doors. For example, when a fire door assembly serves as a smoke and draft control assembly, IBC requires the assembly to be tested in accordance with UL 1784. During this test, “the air leakage rate of the door assembly shall not exceed 3.0 cubic feet per minute per square foot [0.015424 m3/(s • m2)] of door opening at 0.10 inch (24.9 Pa) of water for both the ambient temperature test and the elevated temperature exposure test.”
Where air infiltration is limited to this level, it is difficult or nearly impossible to achieve these values without gasketing at the head, jambs, and meeting stiles. In most locations, a door bottom or sweep is unnecessary to limit the air leakage to the level stated in the model codes. During the UL 1784 test, the area that is at the bottom 152 mm (6 in.) of the door assembly is covered to isolate the measurement of air leakage at the head and jambs, as the leakage at the bottom of the door is of less concern. Where the code specifically states the door assembly must be tested without the bottom sealed during the test, a door bottom or sweep must be used both during the test and on the final assembly installed in the field.
If a fire door or smoke door assembly is required to limit the air leakage when tested to UL 1784, the gasketing products must be listed for this purpose and will be indicated as such in the manufacturer’s catalogs. These doors will typically have an ‘S Label,’ which says the assembly meets the requirement when classified gasketing is installed. In addition to the model codes, the requirement for testing in accordance with UL 1784 (and the same allowable maximum)
is included in NFPA 105, Standard for Smoke Door Assemblies and Other Opening Protectives, which make it applicable to doors that are required to comply with this standard.
Smoke doors
The main source of confusion regarding smoke doors is there are multiple locations where these doors are mandated by model codes, and the requirements may vary depending on whether the assembly is installed in a smoke partition, a smoke barrier, or a wall that is required to limit the transfer of smoke. Smoke doors may be required to comply with NFPA 105, but only where this is mandated by the applicable model code. Here are some examples from IBC.
Doors in smoke partitions
IBC prohibits louvers in doors installed in smoke partitions and requires installation to be in accordance with NFPA 105. However, the rest of the requirements for doors in smoke partitions are dependent on what is mandated by other sections of the code. For example, some sections may require doors in smoke partitions to be self- or automatic-closing by smoke detection, or to have limited air leakage when tested to UL 1784.
Each section requiring smoke partitions (e.g. care suite separations, elevator lobbies) must be referenced to determine the smoke door assembly requirements. Elevator lobby doors in smoke partitions are required to be self- or automatic-closing, but doors in care suite separations in Group I-2 such as hospitals and nursing homes are not. Unlike elevator lobby doors, smoke doors in care suite separations do not require gasketing. Both of these locations require positive-latching hardware. There are also prescriptive requirements in IBC regarding atrium doors in smoke partitions. It is critical to check the code section applicable to the doors in question.
Doors in smoke barriers
In underground buildings and in Use Group I-3 (e.g. detention/correctional centers), IBC requires doors in smoke barriers to be fire door assemblies that meet the requirements of NFPA 80. However, both the IBC and NFPA 101 include exceptions for smoke barrier doors in health care facilities (e.g. IBC: Group I-1, Condition 2, Group I-2, and ambulatory care facilities).
