Air Exchange ..?

Hi all,

Bit of an odd question, but have a small heated growing frame 4x2ft in the greenhouse and with this cold weather its only opened up once or twice a week for watering, otherwise its relatively well sealed.

Its full of plants which are still growing and there is a good air flow around the enclosure from a fan, but did wonder if the oxygen /co2 levels could cause any problems with there being no regular ventilation ?

Suppose the same thing can happen with a bottle garden etc ?

 

Should be fine, they absorb CO2 in the day and then release it at night

 

But dont plants give off oxygen during the day?
What absorbs that oxygen in a sealed environment?

 

They do give off oxygen Pete, but I think they take it up again either through the water in the soil or via leaves. Bottle gardens that are completely sealed work fine with only solar energy to fuel the respiration and growth cycle.