The FSD37SS Combination Fire/Smoke Damper is both UL555 and UL555S Classified.  It is rated as a 1 1/2 hour fire damper and a Leakage Class I Smoke Damper.  It features:

• Triple V-Groove Blades.
• Maximum rating of 2,000 fpm and 4″ w.g.
• UL approval for dual directional airflow.
• Failsafe design, which enables the damper to automatically assume the desired position when fire or smoke (if smoke detector is present) interrupts operational power.
• Controlled closure in not less than 3 seconds and no more than 15 seconds to prevent HVAC and duct damage.
• Automatic remote reset after test, smoke detection or power failure conditions.
  Stainless steel construction.