How do I select a damper actuator for smoke control systems?

Smoke control damper actuators must be UL 555S listed for the specific damper model and meet the operational requirements of NFPA 92 and the IBC — the actuator must fully open or close (depending on the smoke control strategy) within 75 seconds of a fire alarm signal. These actuators require 350°F minimum temperature rating (typically rated for 30 minutes of operation at elevated temperature), dedicated power circuits separate from general HVAC, and spring-return mechanisms that drive the damper to the fire-safe position on power failure. The Belimo FSLF and Honeywell MS4120/8120 series are common smoke-rated actuators providing 120–350 in-lb torque at 350°F for up to 30 minutes. Smoke control actuators must also provide position feedback switches for the fire alarm system to verify operation during testing, and NFPA requires that the entire smoke control system be tested annually with all actuators exercised under actual fire alarm conditions.