BSI - BS 493
Specification for Airbricks and Gratings for Wall Ventilation
|Publication Date:||14 December 1970|
|ICS Code (Iron and steel products in general):||77.140.01|
Class 1 units for external use, and class 2 units for internal use in concrete, clay, cast iron, copper, aluminium steel, plastics and plaster (internal only). Overall dimensions, shape of apertures, unobstructed air space, wall hold, screening, testing of plaster units. Illustrations of typical examples.