~ “Smoke door assemblies are intended to maintain egress, allow for the rescue of the occupants, or allow occupants to remain in an area of refuge. The required duration of smoke protection can be equated with the path of egress. Evacuation typically starts in a room, progresses through a corridor, perhaps passes through a smoke barrier or horizontal exit, and proceeds through an entrance to the exit, which can be a stair enclosure, exit passageway, or the exit discharge. As with fire door assemblies, the longest time of protection is generally required at the entrance to an exit enclosure or horizontal exit, with shorter durations appropriate for preceding doors.”
~ “The path of egress arrangement should also be the case with smoke door assemblies. This arrangement is compatible with the protect-in-place concept as occupants are expected to be moved from one compartment to another for protection or, in some cases, protected in rooms other than the room of fire origin. Occupancies not typical of this scenario include atria, malls, and open office plans. Areas of this sort can be adequately protected by reasonably tight-fitting doors without specific smoke door ratings because of the large volume of space involved.”
~ “When protecting against smoke migration into spaces of large volume, a reasonably tight-fitting door can be considered adequate because of the relatively long time it would take for such a space to become untenable due to smoke. Conversely, the average 8 ft (2.4 m) high by 4 ft to 6 ft (1.2mto 1.8m) wide corridor can become untenable in less than 2 minutes, as shown in a test conducted in California and documented in Operation School Burning, where the fire room door was open.”
~ “Tests indicate that listed gaskets, if properly installed and maintained in accordance with manufacturer’s instructions, do a good job of reducing the smoke infiltration to a sufficient level to provide protection against smoke infiltration through the door assembly.”
~ “Mention should be made of the effects of automatic sprinkler protection on smoke. The activation of an automatic sprinkler occurs early in a flaming fire condition, usually within approximately 5 minutes after visible flaming is observed. Temperatures immediately drop to almost ambient, and smoke is driven to the floor and diffused throughout the available space. Smoke production rate is reduced as the fire size decreases and the temperature of the flame plume is reduced. The temperature of the smoke is also reduced to near ambient. Thus, in a sprinklered building it can be appropriate to treat smoke as if it were at or near ambient temperature. Fewer mitigating measures might be needed to control smoke movement since the production rate of smoke will be reduced. However, under a smoldering fire condition, sprinkler activation can be delayed and this, too, should be considered.”
~ “Depending on the function of the door, its location in relation to the fire, and the movement of hot gases and air, door assemblies might be exposed to elevated smoke temperatures; warm smoke has an assumed temperature at the exposed face of the door at or near 400°F (204°C); hot smoke has an assumed temperature at the exposed face of the door in excess of 400°F (204°C). A nationally recognized standard test for measuring hot smoke temperature leakage does not exist.”
~ “The quantity of air movement through a door gap can be determined by the following general formula:
Q KAP=N
where:
Q = volume flow rate of air
K = orifice coefficient for the gap around the door perimeter
A = area of the gap
P = pressure differential across the door
N = number between 1 and 2 that can be determined empirically
(For more information, see NFPA’s Fire Protection Handbook.)”
~ “Smoke management systems both affect and are affected by smoke door assemblies. Pressurized stair enclosures, for example, are more easily engineered when leakage through the stair doors is reduced. In other areas, pressurization can inhibit smoke flow so that reasonably tight-fitting doors unrated for smoke protection can be entirely appropriate.”
~ “Complete sealing of doors is not always desirable. A disadvantage of complete sealing is the difficulty to open or close doors because of the pressure differential. Some smoke management designs call for some areas to be pressurized. A small pressure acting across the full area of a door can exert sufficient force to make opening a door difficult. A seal must be first broken to equalize the pressure on both sides of the door before the door can be opened easily.”
~ “Smoke doors should take the entire smoke management system into account. The amount of leakage tolerable will vary according to the degree of compartmentation, whether smoke management systems are used, and whether the building is protected by sprinklers.”