BS 6375 is the national application document for BS EN 14351. This part of BS 6375 specifies the exposure categories related to test pressure levels for air permeability, watertightness and wind resistance for external windows and doorsets. It is applicable to all types of vertical windows and doorsets, and includes windows in which the opening lights are not fully framed, e.g. adjustable glass louvres. It is applicable to both factory-glazed and site-glazed products.

The standard excludes patent glazing (see Note) and curtain walls that span across horizontal structural members of floors, but includes the opening lights within a vertical patent glazing or curtain walling system.