AMCA International inmotion Magazine - Fall 2011 - (Page 22)

In addition to the two applications, ﬁre dampers are also available in two basic designs: curtain-type and multiple-blade-type. Curtain-type dampers are the most common and consist of a “curtain” held up by a fusible link. Multiple-blade dampers are similar to control dampers with “blades” located in the airstream. Multiple-blade ﬁre dampers generally offer greater restriction to airﬂow than a curtain-type ﬁre damper for the same size duct. However, multiple-blade ﬁre dampers can be applied in situations when the system air velocities exceed the curtain-type ﬁre damper closure ratings. Multiple-blade ﬁre dampers have been UL tested and are “dynamic” rated for closure at 4,000 fpm and 8.0 in. w.g. Smoke Dampers Smoke dampers (Figure 3) are deﬁned as “a device installed in ducts and air transfer opening of an air distribution or smoke control system designed resist the passage of air and smoke. The device operates automatically and is controlled by a smoke detection system. They can be opened or closed from a remote ﬁre command station if required.”1 Their primary function is to prevent the passage of smoke through the heating, ventilation, and air conditioning system, or from one side of a ﬁre-rated separation to the other. Smoke dampers are operated by either a factory-installed electric or a pneumatic actuator. They are controlled by smoke detectors and/or ﬁre alarms. Smoke dampers are qualiﬁed under UL Standard 555S, UL Standard for Safety for Smoke Dampers, and have two general applications: 1. As part of a “passive smoke control system” in which they close upon detection of smoke and prevent the circulation of air and smoke through a duct, transfer, or ventilation opening. 2. As part of an “engineered smoke control system” designed to control smoke migration using walls and ﬂoors as barriers to create pressure differences. Pressurizing the areas surrounding the ﬁre prevents the spread of smoke into other areas. Smoke dampers have the following installation requirements: Location: Smoke dampers are for use in or adjacent to smoke barriers. They must be installed no more than 24 in. from the smoke barrier. Of course, smoke dampers that are used to isolate air handlers are not limited to this distance requirement. NFPA 90A states that smoke dampers are to be used to isolate air handling units over 15,000 cfm. 22 FA L L 2 0 1 1 Figure 4: Example of a combination ﬁre/smoke damper with electric heat release device. Photo courtesy of Ruskin. Figure 5a: Example of an "out of the wall/partition" combination ﬁre/smoke damper. Photo courtesy of Pottorff. Sleeves and Attachment: Smoke dampers do not necessarily have to be installed in sleeves. They can be installed directly in the duct. The manufacturer’s installation instructions will include the approved method for attachment and spacing of the attachment. Sealing: The joints between the damper frame and the duct must be sealed to prevent unwanted air leakage. Smoke damper leakage ratings are based on leakage through the blades and inside damper frame and not on additional leakage between the damper frame and duct or sleeve. Combination Fire/Smoke Dampers Combination Fire/Smoke dampers (Figure 4) meet the requirements of both the UL Standards for Safety, UL 555 Fire Dampers and UL 555S Smoke Dampers, and applications requirements as described above. They are used in HVAC penetrations where a wall, ﬂoor, or ceiling is required to have both a ﬁre damper and smoke damper. They close upon the detection of heat (via duct temperature) or smoke (via a smoke detector) and “seal” the opening. Unlike regular ﬁre dampers, inmotion W W W. A M C A . O R G A M C A I N T E R N AT I O N A L http://WWW.AMCA.ORG

Table of Contents for the Digital Edition of AMCA International inmotion Magazine - Fall 2011

AMCA International inmotion Magazine - Fall 2011
President’s Message
News
Code Watch
Fan Efficiency Grades: Answers to Frequently Asked Questions
Fans and Atrium Smoke Control
Fire Dampers and Smoke Dampers: The Difference is Important
Fan and Damper Guide Specs Update
Calendar

AMCA International inmotion Magazine - Fall 2011