Ask A Scientist General Science Archive

name Oria
status other
grade other
location NJ

Question - I learned a long time ago that we shoudn't sleep at night
with plants in our bedrooms because they take
oxygen at night and emit carbon dioxide. Is this true or is only old 
stories?
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Well, it's true they do use oxygen at night, but it seems unlikely that 
you'll
do this to the extreme it would take to bother you, let alone hurt you.
The plants use less oxygen and emit less CO2 than 1 person, namely you.
If there is a problem, it's due more to insufficient ventillation than to 
the presence of plants.

If you put enough plants in a small enough room,
and _if_ you keep it well sealed so no fresh air leaks in and out,
then yes, carbon dioxide would slowly build up above it's usual <<1% level.
Slowly elevated CO2 levels are not lethal, but they do create an 
uncomfortable breathless feeling.
I think it would become difficult to go to sleep in such a room. but 
eventually you would be a little fatigued,
and then I think your sleep might be fitful and less restful.

I believe this means that if you are a very rational observer of your own 
feelings,
you may detect for yourself whether the plants in your room are a bit much.
But then, lots of people have problems getting to sleep, without any plants 
in the room.

I suspect that the night-time metabolism rate of plants,
in terms of oxygen intake per kilogram of body weight,
is the same or less than that of warm-blooded animals.
That means it would take hundreds of pounds of plant-life in the same room 
with you,
to emit as much uncomfortable CO2 as one person sleeping next to you in bed.
Most rooms with a few plants don't add up to 10 pounds.
Hmmm, doesn't sound like it will commonly be a problem...
And if it is, creating a little more ventillation is the more helpful 
answer,
because then even your own CO2 is bothering you.

What I wouldn't do is sleep in a closed room with a warm, steaming, 
stinking, giant bin of compost.
For purely scientific reasons. Really.

Jim Swenson
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