FAQs: Life-Safety Damper Application, Inspection and Testing, Part 1 of 2

Fire, smoke, and combination fire/smoke dampers—referred to collectively as life-safety dampers—are an integral part of active and passive fire-protection systems in commercial and industrial buildings, aiding in the pressurization and containment of flames and/or smoke in the event of a fire. Damper experts from AMCA member companies share their responses to the application, inspection and testing questions most asked by customers.

By Dane Carey, James Carlin, Larry Felker, And Kent Maune, AMCA Fire and Smoke Damper Subcommittee

Application

What is the difference between static and dynamic fire-rated dampers?

Static fire-rated dampers are installed in HVAC systems intended to shut down during a fire. Triggered by a smoke detector, an alarm, or a localized increase in temperature, they are designed to close automatically, prohibiting the passage of air through ducts, when fire is detected. Dynamic fire-rated dampers are used in HVAC systems intended to remain operational during a fire. They are designed to operate under airflow and static pressure and to close when the temperature reaches a certain threshold.

When do I use a 1.5-hour fire damper, and when do I use a 3-hour fire damper?

The NFPA 90A Standard for the Installation of Air-Condition and Ventilating Systems, states penetrations in barriers rated for less than 3 hours must be protected with fire or combination fire/smoke dampers rated for 1.5 hours. Penetrations in barriers rated for 3 hours or more must be protected with fire or combination fire/smoke dampers rated for 3 hours.

Does the penetration for a fire damper in a fire-rated wall need to be framed?

Yes. All metal- and wood-framed fire-rated walls have framing requirements for openings in which a fire damper or a combination fire/smoke damper is to be installed (Photo A). Manufacturer installation instructions shipped with dampers and usually available online show or have a link to standard framing details

Which type of heat-responsive device should I use, a fusible link or a thermostat?
Fusible links typically are found on curtain and multiblade fire dampers, while thermostats mostly are found on combination fire/smoke dampers.

Single-use devices, fusible links consist of two strips of metal soldered together (Photo B). When the solder reaches a specific temperature (typically, 165°F [74°C] or 212°F [100°C]), it melts, and the two strips of metal separate, enabling a damper to close.

A thermostat (Photo C) is a bimetal thermal disc designed to cut power to an electric damper actuator when a specific air temperature (typically, 165°F [74°C], 212°F [100°C], 250°F [121°C], or 350°F [177°C]) is reached. Many thermostats can be reset in the field once a damper has been inspected and found to be free of damage.

Do building codes explain how to install fire, smoke, and combination fire/smoke dampers?

Model codes refer to manufacturer installation instructions and damper listings. Though many manufacturers’ installation instructions are similar, the differences, however slight, may be important. Therefore, be sure to review the instructions for the specific damper to be installed.

How do I know whether I need a smoke damper with a leakage rating of Class I or one with a leakage rating of Class II?

Consult your local codes for leakage requirements. If your local codes do not specify a minimum leakage for your application, then refer to the national codes.

For most applications, a minimum leakage rating of Class II is required. Class II leakage means a damper was tested and is approved to leak less than 20 cfm per square foot at 4.0 in. wg (102 l/s/m2 at 1.0 kPa).

For applications such as hospitals, schools, and stairwells, a leakage rating of Class I is required. Class I leakage means a damper was tested and is approved to leak less than 8 cfm per square foot at 4.0 in. wg (40 l/s/m2 at 1.0 kPa).

If a leakage rating is not specified, the designer will need to determine how tight a penetration should be sealed during a fire event.

Inspection and Testing

How do I know if my damper’s ratings are current and correct per the submittal?

Per UL requirements, the damper should bear a label indicating the maximum static pressure and airflow the damper is approved to open and close under. Additionally, you can search UL’s UL Product iQ website. The minimum airflow and static pressure for a UL 555S listing is 2,000 fpm (10.2 m/s) and 4.0 in. wg (1 kPa) at 250°F (121°C).

How do you test auxiliary switches on fire dampers (actuator-driven only), smoke dampers, combination fire/smoke dampers, and actuators?

Make sure the switch package is not connected to anything. With the damper closed, check for continuity across the switches to determine the closed wiring. Next, power the damper open and check for continuity across the other set of wires. The most common containment-damper wiring is shown in Figure 2.

How do you remotely test actuator-controlled fire, smoke, and combination fire/smoke dampers?

Manufacturers provide a number of different configurations of panels, with options such as keyed switches, momentary switches, and selector switches. All use the same concept shown in Figure 3.

When a damper is open, a green light or light-emitting diode (LED) on the test panel will be on. Activating the test switch will cut power to the actuator and, thus, close the damper. Once the damper is closed, the green light or LED should be off, and a red light or LED should be on. Deactivating the test switch will restore the power, and the green light or LED should be on again. The test then is finished. Following installation, damper-blade position should be visually inspected to confirm the wiring, and switches are correct and operational.

Alternately, a fire-alarm or building-automation-system module can take the place of a remote-test panel and allow testing from a central control panel (Figure 4).