Is it permissible to use inside combustion air in buildings of ordinary construction?

Using inside combustion air in buildings of ordinary construction is not permissible because it can pose several safety and operational risks. In buildings classified as ordinary construction, it is critical to ensure that combustion appliances have a reliable source of fresh air. Inside combustion air can lead to combustion inefficiency, potential backdrafting, and the introduction of harmful gases into the living space, which could compromise indoor air quality and tenant safety.

Typically, combustion appliances require air that is not contaminated by other indoor pollutants, and outside air is preferred as it is less likely to contain harmful byproducts from household activities. This ensures that the combustion process is efficient and that the venting of combustion gases occurs without creating a hazard within the building.

While there may be scenarios in specialized designs or certain zones where modifications could be made to allow for inside air use, this is not a standard practice in ordinary construction due to the significant risks involved.