1. Containment of fire and/or smoke to maintain building compartmentation. These are installed based on Chapter 7 of the International Building Code (IBC) which is the primary model code. These are sometimes referred to as passive systems although the dampers do close and fire alarms operate when a smoke detector operates.
2. Engineered smoke control systems use dampers, fans, and some architectural features in a wide variety of applications. These are based on Chapter 9 of the IBC.

In the Americas smoke dampers are always actuated; fire dampers use mechanical means of sensing heat (fusible links that melt and gravity or spring release for closure). They and can be actuated for ease of periodic inspection and maintenance. Smoke must be sensed using electrical sensing – smoke detectors. Spring return actuators are used to close the dampers and then the actuator motor used to open the damper. Combination fire and smoke dampers are actuated due to the smoke function.

Periodic testing of life safety systems and dampers is required by the codes. While there is some state or local variation, the requirements are shown in Chart 1. While the focus of this article is the dampers, the entire smoke control system is required to be tested according to the schedule labeled “Smoke Control Systems & Dampers.” A clear distinction must be made among the damper applications in order to determine the schedule that conforms to codes. The second part of this article explains the differences among the dampers and applications.

Chart 1: Periodic testing requirement for dampers.

Allow us to recommend this publication: Dampers and Airflow Control written by Laurence G Felker and Travis L Felker provided by ASHRAE Special Publications.

A damper restricts airflow by obstructing the duct. Some multi bladed dampers have flanged frames to which ductwork is butted, and the open area is restricted only by blades and hardware. Most dampers in the U.S. are inserted into a sleeve, duct, or wall, and the frame obstructs part of the open area. The maximum free area for this type is about 80% for 48 x 36 in. (1200 x 900 mm) and larger-size dampers, and the minimum is about 40% for an 8 x 8 in. (200 x 200 mm) damper. The frame takes up most of the reduced space. The free area changes slightly with comer braces, linkage in airstream versus frame, airfoil versus triple V, and with type of frame. In round dampers, the blade is the only significant restriction.

The pressure loss through any damper is a function of the entering flow profile, the free area ratio, F,  of the open damper area to that of the damper frame or wall area, the geometry of the damper installation, and the exit conditions as air leaves the damper. The most complete testing of dampers was performed for ASHRAE’s Research Project 1157. A complete analysis of the results is available in the book Dampers and Airflow Control published by ASHRAE Special Publications. Not only the full open losses, but also the modulating characteristics of dampers are experimentally defined.