6.8 Fireplaces, chimneys and flues

6.8.9 Gas – combustion air

Installations shall be provided with an adequate supply of combustion air.

Table 3: Combustion air to gas appliances

Gas(1) up to 70kW net input
England, Wales and the Isle of ManIf design air permeability is less than 5.0m3/h/m², then 500mm²/kW of the appliance is the rated (net) input
If design air is permeability greater than 5.0m3/h/m²), then 500mm²/kW of the appliance is the rated input (net) over 7kW
ScotlandAs BS 5440-2 (as England and Wales)
Northern IrelandUp to 8kW rating, 450mm²/kW
Over 8kW, add 450mm²/kW for each kW above 8kW

Notes

1. Decorative fuel effect gas appliances should have a provision for combustion air complying with the relevant part of BS 5871 and relevant Building Regulations. (Generally, a minimum of 10,000mm²/kW of purpose-provided ventilation is required. Air vents should be direct to the external air or to an adjacent room or internal space, which has an air vent or vents to the external air of at least the same free area. Air vents should have an aperture dimension no smaller than 5mm).

Last updated: 2nd January 2024

Back to top ⇧