Is this Safe???? 1st grow

[stinkyattic]

i thought plants dont use co2 in there dark period.......

The two cycles of photosynthesis each use air-borne gases. One uses O2 and the other uses CO2.
The net is that the plant uses more CO2 than O2 and has a net INTAKE of CO2 and net OUPUT of O2. But you can still suffocate the plant or at least retard its growth by depriving it of either of those.