Share 'Drilling through a flue pipe of a power-vented combustion appliance'

Here is a dilemma for a BPI-certified building auditor - should I or shouldn't I drill through a flue pipe of a power-vented combustion appliance? At first it seems obvious - don't. The BPI standards state that clearly. However, in the industry I see a number of people do that anyway. And even one of the best demo videos of combustion safety test performed by a BPI certified guy you can find onli…