Seal wall penetration for decentralized ventilation airtight

Hello everyone,

in a few days a blower door test is scheduled. We have installed a decentralized ventilation system, therefore there are several wall penetrations.

These should be sealed for the test. Do you have any tips on how I can do this best? Tape over them? Stick something in? What do you think?

I have attached an example picture:

Make sure there are no sharp edges, inflate a sturdy balloon in the hole and seal it.

Absolutely tight and removable without residue.

You don't have to do that, the tester does it. At least he did it with the chimney openings in our case.