I can't find any suggestion that the Ovei pod is able to support a pressure differential in either direction. The mention of gas valves suggests that the OP may be contemplating an oxygen-rich, rather than hyperbaric, environment.
Whatever is contemplated here, it should be done with care, and with a thorough understanding of all the issues and risks involved, or not done at all.
I echo tdm3.
If you are going to use oxygen then this requires special valves, oxygen is not something to be played with.
So some clarification please.
The flow of what gas are you aiming to control?
At what pressure are you aiming to do it.
There are probably you-tube videos that show experiments on what effect even a few % increase or decrease in oxygen content of the atmosphere can do.
Nature has settled on 21.5% in the atmosphere for a very special reason.