How to add oxygen to indoor air without opening windows?
You should also have in mind that, meanwhile plants produce oxygen through photosynthesis, they also carry out aerobic respiration. In short, this process requires oxygen which is normally not a problem during daytime as photosynthesis covers the oxygen needed. Nonetheless, during nightime, plants remove oxygen from the atmosphere and do not replenish it. This is why nurses normally remove plants from hospital rooms at night. So if you want to put plants in your room, have in mind that is best to take it outside during the night.

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