An apparatus for sealing a doorway, more particularly, an all purpose gasket structure capable of sealing a doorway against the entry of water, smoke, and fire. The gasket is primarily an elongated silicone rubber structure having a ridged rectangular cross section for mounting to a gasket retainer. The gasket also includes a crush zone which collapses inwardly when pressure is applied to the gasket surface, resulting in improved sealing and the blockage of water intrusion paths. The gasket may further include an intumescent section within the elongated silicone rubber structure. In the sealing arrangement, the gasket is arranged within a gasket retainer that surrounds the doorway, thereby sealing boundaries between areas of personal egress.