Air Control Products

For applications where building codes require a leakage rated (smoke) damper as part of a static smoke control or dynamic smoke management system.  Smoke dampers are intended: (1) to restrict the spread of smoke in HVAC systems that are designed to be automatically closed down in the event of a fire or (2) to control the movement of smoke within a building when the HVAC system is operational in engineered smoke control systems.

In September 1983, Underwriters Laboratories issued the first edition of Standard UL555S to evaluate the leakage characteristics and operational reliability of smoke dampers together with a qualified actuator for use in engineered smoke control systems.  The current fourth edition was issued June 1999.

UL qualification and leakage classification of a damper design require the testing of a minimum of three sizes of each design, representative of the range of sizes available.  The configurations must be a minimum width x maximum height, maximum width x minimum height and maximum width x maximum height.  The performance of the worst damper determines the damper/design class.

In addition to leakage testing, each damper must pass the following for operational reliability:

1. 20,000 cycle operational test
2. Opening and closing against system pressures of 4" w.g. minimum and air velocities of 2,000 fpm minimum up to 4" w.g.
3. Salt spray and dust loading tests
4. Optional elevated temperature tests (250°F standard, 350°F+ optional).

The damper design must maintain its leakage classification after 1 and 4.  Leakage and temperature classifications are detailed as follows:

LEAKAGE CLASS	MAXIMUM LEAKAGE CFM/ft2		TEMPERATURE CATEGORIES
	@1" W.G.	@ 4" W.G.
l	4	8	ambient (60 - 100°F) 250°F 350°F +
ll	10	20	ambient (60 - 100°F) 250°F 350°F +
lll	40	80	ambient (60 - 100°F) 250°F 350°F +

Dampers and their actuators may be required to operate under elevated temperatures during a fire condition in a dynamic smoke control system.  UL classifies the actuators for use with smoke dampers and their performance either at ambient or an elevated temperature.  The performance of a damper/actuator at an elevated temperature is usually limited by the actuator's capability.

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