oxygen production

[K N and P J Harris]

Oxygenation by plants.
The problem is that the amount of oxygen produced is related to the 
light input. Low light equals low oxygen output. Also, if the lights go 
out at night - those same plants will be consuming oxygen. Lack of 
oxygen is usually not the problem - the increase in carbon dioxide is 
much more likely to make the environment unpleasant. Lots of water 
containers about, changed frequently, will mop up a lot of carbon 
dioxide and very little oxygen (different solubilities) but then (maybe) 
you will have a humidity problem. It's all swings and roundabouts. 
Peter, Reading, UK.