Some precocious, health-conscious housewives keep lecturing us that we must by no means keep any plants in the bedroom, because they simply “breathe away” our valuable oxygen at night! If you google for the corresponding terms, you get the impression that 90 % of the people are firmly convinced of this claim. Frightening to see how many of them seem to lack even the most simple logics: It is well known that, despite all the warnings, many people do have plants in their bedrooms, and yet they still enjoy good health. Shouldn’t this fact be enough counterevidence?
In the desperate hope to weaken this silly myth a little, I will now make a calculation. It is true that plants do not produce oxygen at night, but only consume it; however, this consumption will at most – if ever – come close to that of a human. Thus we will now have a look at the oxygen consumption of a human.
Imagine a room of 3 x 3 m with 2 m to the ceiling. The volume of this room is 3 x 3 x 2 = 18 m³. This means that there are 18,000 liters of air in this room. Out of these 18,000 liters, about 21 % are oxygen and 0.04 % are carbon dioxide. (The rest consists of other gases which do not interest us.) So there are 3,780 L of oxygen and 7.2 L of carbon dioxide in the room. In a diagram, it looks like this:
Now let’s imagine a man who spends the night in our imaginary room. He sleeps for 8 hours, drawing about 18 breaths per minute with a volume of 500 ml each. He thus breathes through 4,320 L of air; the remaining 13,680 L in the room remain unchanged. The exhaled air contains only 16 % oxygen, but 4 % carbon dioxide. Thus our person exhales a total of 691.2 L oxygen and 172.8 L carbon dioxide. If we add these values back to the 13,680 liters of unchanged air, this results in an oxygen content of 3,564 L (19.8%) and a CO2 content of 178.27 L (0.99%) for the whole room. Therefore, after one person sleeping in a small room for 8 hours, the distribution looks as follows:
The difference is shocking. No wonder people keep dying from lack of oxygen while sleeping. Especially parents’ bedrooms, youth hostels and other multi-person sleeping accommodations have often been the scene of surprising deaths that could have been avoided if only we would raise the public awareness of the immense nocturnal oxygen consumption. (Irony off.)
But seriously: A few small plants in the bedroom will in no case draw more oxygen from the air than we do ourselves in our sleep (and even then there would still be 18.6 % oxygen remaining in our example room). A life partner who is sleeping in bed next to us is a far greater threat to our nightly breathing air than a plant. So if anything, you should throw him/her out first. :P
There is yet another argument that I find quite funny: If the oxygen requirement of plants at night was indeed as high as is always claimed, you would suffocate immediately when taking a night walk in the forest. :P And now have fun greening your bedroom!