FIRE CODE: Designed to automatically seal off fan and duct from the rest of the dwelling once the temperature of the air exceeds that of the fusible link. UL approved for PA500V, PA700V, PA900V, PA1100V, VIP70, VIP90 and VIP110 for ceiling/floor and ceiling/roof wood truss construction. Classified by UL to function as a heat barrier, when installed as shown, in UL floor/ceiling design #’s L550, L562, L574, L579 and roof/ceiling design #’s P531, P538 and P545.