ᐅ Concrete inside the ducts of the mechanical ventilation system with heat recovery

Hello!
We have a huge problem right now.
A few weeks ago, our installer placed the ductwork for the mechanical ventilation system between the steel layers of the ground floor ceiling.
The next day, the concrete ceiling was poured with cast-in-place concrete.
Today, when the installer wanted to connect the ducts and so on, it was noticed that concrete had flowed into two of the ducts.
Now the question is how this could have happened.
Could the ducts have been damaged by the concrete workers, or are they sturdy enough that this is unlikely?
Otherwise, the only possibility would be that the duct connections didn’t hold and came apart.
Do you have any idea how something like this might happen?
And above all, can someone tell me what can be done now to fix it?
Should the ducts inside the screed be reinstalled?

It would be great if someone experienced could give me a few tips so we don’t look clueless at the appointment with the installer tomorrow. Of course, everyone will probably try to avoid taking responsibility for the damage to avoid paying for it...

Phew, I doubt whether the pipes can be easily cleared this way. However, I’m not an expert.

What is definitely still possible: placing flat ducts on the concrete ceiling (before the screed is applied).

Purely out of curiosity: Would it be possible to remove the ceiling and pour new concrete?

You can certainly do a lot yourself. But it costs a) time and b) money.

However, if someone has to (or wants to) teach a or b, that’s a different matter.

Who is supervising the construction work (architect / site manager?), and who pays their salary? Without expertise, I wouldn’t want to discuss matters with either of them alone.

It is rather unlikely that the concrete contractor caused the damage... the connections probably came loose...

So, we have now reached a compromise.
Since two of the pipes are completely filled with concrete, a connection must have come loose somewhere. This couldn’t have happened due to any minor damage to the pipe.
Of course, it’s impossible to determine who is responsible. Maybe the plumber didn’t tighten the connections enough, or the concrete contractor was careless and rough during the concrete pouring, causing the connection to come loose.
In any case, they are now sharing the work and costs.
The concrete contractor will make two core drills through the ceiling, and the plumber will then re-route the two pipes on the concrete slab.
I was really shocked at first, but in the end everything was resolved quickly and smoothly.