When the door is opened, the internal seals of RESSA automatic door sweep will automatically rise from the ground. When the door is closed, the internal sealing strip will be down automatically to performance the tight sealing Some models of this type seal can be fully hidden in the door bottom groove, the door beautiful surface will not be affected by installation of the seal. RESSA automatic door sweeps includes three types with nearly fifty models, which include Mortised automatic door sweeps Full mounted automatic door sweeps Fireproof Intumescent automatic door sweeps RESSA fireproof intumescent automatic drop door seal is combined by automatic drop door seals and reinforced by fireproof intumescent seals, it has the performance of sealing and fireproofing. The automatic bottom door seal control the movement of the inner sealing strip through mechanical movement. When the door is opened, the internal seals will automatically rise from the ground. When the door is closed, internal sealing strip will be down automatically to seal the space between door and ground. When meet fire, the intumescent seals part will start to expand to fulfill the space between door groove, door frame and ground to prevent the smoke and fire spreading. Please contact with us on the detailes on each model according to your specific requirements.