Carbon Dioxide has an atomic weight of 44. Air has an atomic weight of approx.
29 (28 for N2 and 32 for O2). This means that Carbon Dioxide is heavier than
air.
However near the ground there is a lot of air movement so the various components
in the atmosphere are mixed. The amount of Carbon Dioxide is not very high, this
is due to the sea is absorbing Carbon Dioxide and trees etc. are converting
Carbon Dioxide back to oxygen.

In a place with no air movement like the bottom of a dry well, if you put a lot
of organic materials there to rot, Carbon Dioxide will accumulate at the bottom
and it will displace the air.

In a bee hive, the effect of hot air rising could be stronger than the effect of
that Carbon Dioxide is heavier than air.

As I am a newbee bee keeper I will not comment further.

Best regards

Knut S.Helland
Bergen, Norway.