Respiration of an animal cell media
Supply of cells growing in adherent culture is unproblematic, as long as you don't fill too much media in the petri dish/cell culture flask.

Oxygen supply here work by diffusion which is getting more problematic if the layer of media covering the cells gets to thick. I usually follow the recommendations of Corning for the amount of media to be used in the flasks/dishes:



The complete information can be found here, other companies have similar data sheets available. With these amounts I do a lot of cell culture work and I have no growth problems.