Domestic gas pipework located in voids which may need ventilation.
Width of duct in mm
Depth of duct in mm
Height/length of duct in m (Optional)
Requirement of vent at high level (in cm2)
This calculator is based on BS6891 (Domestic pipework), regulation 8.11.1 which is in m2 when most gas engineers measure in mm and air vents are purchased in cm2, plus then the division of required vents is by 150 - All rather complicated. As such, let's concentrate on measuring the duct in mm and let the calculator do the rest.
