Does your home or enclosed community have proper air production and filtering?
How much oxygen do the plants produce? How much carbon dioxide do they eliminate?
Do you drive combustion engine vehicles, or produce other sources of pollution? How are they dealt with?
Be it humans, livestock, pets, or scenery animals, you must calculate how much oxygen is being used and carbon dioxide produced.
Oxygen from waterEdit
It is rather simple to build something which uses electricity to split water molecules into hydrogen and oxygen.