Clean room doors, Clean Room Doors. ... Entryways, outlets and other openings are critical components of cleanrooms. Great care is taken to ensure the cleanliness of the inside of a room, but an equal amount of effort is required for doors, windows and pass-through. A fire door is a door with a fire-resistance rating (sometimes referred to as a fire protection rating for closures) used as part of a passive fire protection system to reduce the spread of fire and smoke between separate compartments of a structure and to enable safe egress from a building or structure or ship.