Mounting of the controlled residential ventilation ducts in the flat distributor

Hello everyone,

since the ventilation pipes have already been damaged in several places, I have dealt with it a bit more intensively. Now I noticed that all pipes were fixed to the flat distributor in the concrete ceiling using set screws. Unfortunately, I can't find out which manufacturer was installed in my case so that I could do some research. In general, I would say that screw heads have no place in a ventilation duct.

Attached are a few photos. Can you give me some keywords/ideas on how I can find out more here? I don't even want to approach the general contractor with a suspicion; I first want to know exactly myself whether this is inadmissible.

Thanks in advance for your assessment.

What kind of suspicion? In a pipe, no matter what medium... gas, water, air, Pupu, oil, mud, durum wheat semolina or pizza sauce... a constriction must never be produced because some people, who often have bad luck when thinking, intentionally install constrictions. Sooner or later... rather sooner, dust will stick there. Dust attracts dust, that is practically a fundamental law of dust... then it gets nice and damp there because your moist indoor air is blown in. The dust is happy and starts inviting its buddy mold...

Is there the slightest chance to remove these screws afterwards? If yes, then do it. Now...

It MAY in some cases be quite permissible to fasten the ventilation duct to the distributor with screws (larger spiral seam ducts, etc.), but: unfortunately, I do not see any pictures. If I had them, I could ask a TGA planner (in the family).

It CAN possibly be allowed to attach the ventilation duct to the distributor with screws (larger spiral seam ducts etc.), but: Unfortunately, I don't see any pictures. If I had them, I could ask a building services planner (in the family).

I had attached three pictures to my post, are they not being displayed? Because I can see them.

I see them now too, strange. The forum sometimes does things ... Looks not permissible to me at first ... Usually there are rings / seals that go around the pipes and then "click" into place at a suitable position. This seals and fixes the pipe against the valve or distributor. I'll ask ...

So the TGA planner says about the screws: Looks impermissible, probably not watertight against the initial water from the concrete. As the site manager, he would not have approved this type of fastening ;-)

But he also says: In case of doubt, ask the manufacturer regarding permissibility