Abstract: A lightweight, free-standing, expandable shelter (10) providing protection against chemical and biological agents and against nuclear fallout. The shelter (10) has a frame comprising a series of U-shaped ribs (12) spaced and held parallel by a series of reinforcing members (16) connecting each adjacent pair of ribs (12) on each side of the shelter (10). A cover (11) made of flexible material which is resistant to chemical and biological agents is attached to the frame. An airtight floor (18) is attached to the cover material (11) so that the shelter (10) can be pressurized to a pressure of about one inch water gauge above ambient pressure, to prevent reverse air flow of contaminated air into the shelter (10). A blower (20) for pressurizing the shelter (10) and a filter (22) capable of filtering out chemical and biological agents are connected to the shelter (10).

Abstract: A snap slit door having at least one panel and a flat closure means used to reate tension in the door panel or panels, such tension acting as the closure force generated by the closure means for the door panel or panels. The flat closure means may be adjustable such that the tension and resulting resistance to opening is variable. Said door panel or panels may be of any pliable material to enable use of the panel or panels without hinges, and further to render the flat closure means operational. The panel or panels may be held in the closed position by any means which will self-release upon the exertion of a requisite pressure differential between the inside and outside of the panel or panels, effectively relieving the pressure differential. One such effective self-releasing closure means is a hook and pile patch arrangement.