Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 24·2.14
Sizing of permanently open air vents
Air vents must be sized with sufficient free area (or equivalent for complex designs) to accommodate the appliance, accounting for obstructions like grilles and mesh.
A permanently open air vent should be sized so that the free area, or the equivalent free area of a more complex design, is sufficient for the appliance to be installed, taking account where necessary of obstructions such as grilles and anti vermin mesh.
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