Vapor-tight lights prevent dust and moisture from entering the fixture and damaging internal wiring and components. Also called gasketed fixtures, their housing and lens fit tightly together and seal with a gasket. They illuminate wet, damp, or humid locations, such as locker rooms, loading docks, public transportation shelters, and parking garages. Fixtures with washdown ratings carry an IP rating indicating the level of protection they provide against liquids. Round fixtures hold a single bulb to light small areas. Linear fixtures have a long body that spreads light over a wide area for more coverage than round fixtures. Troffers conceal their wiring and most of their housing within drop ceilings. Retrofit kits convert existing vapor-tight fixtures to energy-efficient LED technology to reduce operating costs.