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Re: Plants cause oxygen deprivation at night???????

  • Subject: Re: Plants cause oxygen deprivation at night???????
  • From: "mossytrail" <mossytrail@hctc.com>
  • Date: Tue, 16 Feb 2010 18:29:12 -0800

Sleeping with head under the covers scares you?  What are
your bedcovers made of?  Plastic?
> I can?t add to the ideas Steve Marak presented, but I can
> try some numbers. I hope the readers of Aroid-L will work
> through my numbers here. It would be bad enough for me to
> look like an idiot because I overlooked something that
> changes the results by a factor of a hundred or so, but it
> would be worse for the wrong results to stand without
> correction.
> I asked a friend who did his doctoral work on plant
> respiration and got the approximation that the emission of
> CO2 in the dark is unlikely to exceed 4 micro moles per
> square meter of leaf surface per second. This is the same
> as the O2 taken up. Say our plants have a leaf area of one
> meter. Let?s say for the sake of argument that both upper
> and lower leaf surfaces emit at that rate, so our plants
> use up 8 micro moles PER SECOND (please excuse the upper
> case, but when we think of a whole night the seconds
> really add up).
> In an 8-hour night, we have the 8 micro moles/s x 3600 s/h
> x 8 h = 230400 micro moles of oxygen the plants take up.
> That is only millionths of moles, so it amounts to 0.23
> mole. That got the number back down in a hurry.
> How much oxygen was in the room to start with?
> A room 4 m x 4 m x 2.4 m has 38.4 cubic meters of air.
> That is 38400 liters.
> At room temperature, a mole of gas is about 25 liters, so
> the room has 1536 moles of air.
> If we say the air in the room is 20 % oxygen, we have 307
> moles of oxygen to start with.
> How much of the total oxygen in the room did the plant
> use? It is 0.23/307 = 0.075 %.
> What about our oxygen-starved sleeper?
> A person breathes out about 900 g CO2 per day or about 300
> g in an 8-hour night.
> CO2 has a mole weight of 44.
> 300/44 = 6.8 moles CO2 emitted = moles O2 taken up by a
> person in the night.
> The 6.8 moles of oxygen used by the sleeping person
> amounts to only about 6.8/307 = 2.2 % of that available.
> How do the plant and the sleeper compare? The plant uses
> 0.23/6.8 = 3.4 % as much.
> With all the guessing (?approximation? in science-speak),
> none of the numbers has any meaning unless it?s rounded
> off to only one digit. You can insist that a sleeping
> person uses less oxygen than an active one, the room is
> smaller and the plant larger, but that doesn?t change
> anything. A good-sized plant surface won?t reduce the
> oxygen content of the room by much more than a tenth of a
> percent, and that is only about three percent of what the
> inhabitant uses up.
> If the sleeper is oxygen-starved, he or she probably isn?t
> breathing right. It can?t be blamed on the plant. I?ve
> known people who slept with their heads under the covers.
> That does scare me.
> Walter Turner

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