Smoke Control Through Automatic Door Release

Last month, we talked about the use of a noncode-compliant ancillary relay when monitoring a code-compliant smoke alarm system in a residential setting. This month, we will tackle the job of explaining exactly what the third-party listing on this relay allows you to do when installing code-compliant systems — whether it’s in a home or a commercial building.

Most of the ancillary relays now on the market are listed for the specific applications of door release and the activation of bells and lights, as stated in the manufacturer’s installation instructions. The activation of lights helps illuminate the way out of the structure for the occupants.

If you recall, it was pointed out in last month’s column that no matter what the application may be, there is no supervision between single-station, tandem-line smoke alarms and the coil or other input circuitry of this relay. Thus, no matter what you do with it, similar liability issues exist for both listed and unlisted applications.
Releasing Doors Via Ancillary Relay Another use of an ancillary relay, in conjunction with single-station 120VAC, tandem-line smoke alarm systems, is door release, which is directly related to smoke control. The same applies to almost any spot-type smoke detector or smoke detector base that is equipped with an ancillary relay listed (see sidebar on page 28) by a third-party organization for door release/smoke control, conventional or addressable, low- or high voltage.

Smoke control is the act of compartmentalizing a facility in such a manner that smoke from a fire cannot rapidly spread throughout a building. National Fire Protection Association (NFPA) defines it in Section 9.3.18 of NFPA 101, 2000 Edition, as “ … the purpose of such smoke control systems shall be to confine smoke to the general area of fire origin and maintain use of the means of egress system.”

The two most common uses for smoke control involve facilities that contain a large number of people or when the fire load of a facility is such that the AHJ considers it to be a higher risk than normal. In either case, single-station 120VAC smoke alarms, tandem or otherwise, can be used to close fire doors and, in some cases, control heating, ventilation and air conditioning (HVAC) systems. The intent is to prevent the rapid spread of smoke throughout a building involved in a real fire situation.

According to Section, when smoke alarm units are used to release doors, they must be listed for smoke control.

The use of 120VAC smoke alarms for the automatic release of smoke doors in a facility was once a common method of smoke control. Today, open-area smoke detectors are most often used. In this next section you will learn why.
How Isolation Controls Smoke Smoke control can be accomplished by a number of methods, not just 120VAC single-station smoke alarm units.

No matter what the automatic means of smoke/fire detection you use, the release of one or more smoke doors is usually accomplished through an electromechanical device that holds the doors open until smoke is detected. When detection occurs, the result is the mechanical or electromagnetic release of the door(s). This acts to isolate the affected area from other portions of the structure so smoke cannot spread throughout.

When architects design buildings and generate blueprints, provisions must be made for door release. This is especially true where the likelihood of propping exists.

Fire technicians involved in retrofit installations should advise their clients concerning the benefit of door holders.

According to “Guide to Fire Alarm Systems” by Ventcroft Internal Fire Technical Support (page 13): “Consider fitting door holders/closers onto doors that might otherwise get propped open. Doors leading to stairwells should not be fitted with door holders. There was an old GLC regulation that requires a smoke detector to be fitted within 2 meters of either side of the door or pair of doors fitted with a door holder(s)/closer(s) and many authorities (i.e. West Sussex) still require this.”

There are several ways according to NFPA 72 to meet this recommendation. They include door frame-mounted smoke detectors; smoke detectors and smoke alarms in standalone mode; and open-area smoke detectors as part of a fire alarm system.
3 Approved Ways to Control Smoke The first method involves the use of a special electromechanical door closer equipped with an automatic smoke detector. In many cases, these smoke detection/door closers act to hold one or more doors open until smoke is detected by the internal smoke sensor.

As mentioned earlier, the second approach — use of standalone smoke alarms and smoke detectors — is not as prevalent today as it was in years past. However, this method is still used and fire technicians must be acquainted with it in order to install and properly maintain what’s out there.

When used for this purpose, these detectors/alarms must be listed for smoke control by a third-party listing organization, such as FM Approvals of Johnston, R.I., which is also commonly referred to as Factory Mutual, or UL.

Open-area smoke detectors are the most prevalent method of controlling smoke doors in use today. This is because these detectors not only will release one or more smoke doors, but also provide open-area fire protection. You can kill two birds with one stone using this type of detector.

A word of advice regarding the current and voltage capacity of the relay used for door release. Be sure to read the specifications of the ancillary relay with the required current draw in mind. Also, be sure to use the relay called for by the manufacturer of the equipment.
Coming Up: More on Smoke Control Next month, we will explore additional means of smoke control, the positioning of open-area smoke detectors and relay capacity.

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