Attic peak - floor made of chipboard

Hello everyone, we are currently flooring new floors or having them installed. In the attic, the subfloor consists of chipboard panels that were laid with a rather small offset (cross joint). According to the floor fitter, this is not professionally done. My question is: The panels creak, maybe they can still be better screwed down. Due to stability (the chipboard panels are from 1995), would it make sense or even be necessary to switch to OSB panels? Is it to be expected that such old chipboard still contains toxic substances?

Both chipboard and OSB are not vapor-permeable. So depending on the floor structure, moisture underneath might not be able to escape well - > risk of mold. Has the attic so far been heated or was/is it supposed to be living space? Do you know what the chipboards are attached to?

I don't understand why the floorboards on which the junk is standing in a storage room wouldn't be good enough (?).

Would it make sense or even be necessary to switch from particle boards from 1995 to OSB boards due to stability? Is it to be expected that such old particle boards still contain toxic substances?

With new particle boards adhering to current limits, you will get more pollutant exposure than the old ones could still have emitted after 27 years.

The chipboards can stay in, so from that perspective the issue is settled for now. that is indeed a living space :)....at least it is planned that way.