Hello, im designing a room and ran into a new concern

here is my setup:

5x5x8 sealed (guys at the show say i dont need fresh air cause of co2)

independent exhaust of lighting

properly rated fan and scrubber not exhausting but recycling the air

my questions are:

1) is it true that because of the co2 enrichment that i dont need fresh air?

2) do the scrubbers neutralize the odor only or will they waste my co2 even though my air is being recyclyed only

much thanks for those who can help