BS 493-2(1970) : LATEST

Describes requirements for two classes of wall ventilating units. Class 1. Airbricks, for use in external walls and Class 2. Wall ventilators or gratings for internal use. Some typical examples of designs are shown in Figs. 1, 2 and 3. Other patterns may however be supplied, provided they comply with the requirements of this standard. Covers definitions, manufacturer's certificate, marking, materials and design, workmanship, dimensions, apertures, wall-hold, additives, screening and testing of plaster units.