The FSD35RA is a 1 1/2 hour UL555 Classified Fire Damper and a UL555S Class III Classified Smoke Damper. It is designed for vertical installation and features:
Installs completely from one side.
Triple Vee Groove Blades.
Rated for 2,000 fpm and 4" w.g.
Easy mounting strap installation that doesn't require damper sleeve or mounting angles.
Fail-safe design, which enables the damper to automatically assume the desired position when fire interrupts operational power