Oxygen-production of plants

Plants produce carbohydrates through photosynthesis. For the process they use carbon-dioxide, water and the energy of sunshine. As a result, oxygen is released and water is evaporated.
Plants play a very important role in sustaining the eco-system of the Earth, as they constantly reproduce oxygen.
However, to improve the air inside a room simply with plants, you would need a huge surface of leafs.

Airing a room is a much more effective way to provide the necessary amount of oxygen than using indoor plants. Due to experiments at the University of Cologne, indoor plants provide 1-2 % of the oxygen needed. If we wanted to improve air quality only by filling the room with leafy plants, the room would look like a piece of jungle.