Wood stove independent of room air?

The chimney has a clay pipe inside for the flue gases. This is surrounded by the fresh air supply, then lightweight concrete on the outside. A LAF chimney. The drilling into the clay pipe for the flue gases was already done at the factory. Wall collar made and finished. For the fresh air supply, I need a separate drilling at the bottom of the chimney accordingly. We want to connect the whole thing ourselves. As already mentioned, the chimney sweep has the final say and demanded the pressure monitor despite dibt certification.