Re: oxygen concentration in a room

Jim wrote:
I need some help in trying to calculate the percentage of oxygen existing in
a closed room. This is partly just for my interest, but there is a
practical side to my question also.

I live in a recently built house that is one of these "super-insulated"
structures with little outside air exchange except what is forced via fans.
During the winter months I live primarily in a couple of rooms closed off
from the main house to save on heating bills.

I have equipment that very accurately measures the carbon dioxide level in
real time, that is located in my main living area. I live at 3000 feet
elevation, and the house is all electric; no oxygen consuming heating, not
even a wood buring stove. I don't have any way of directly measuring o2 in
the house.

The measured co2 in my living area ranges from approximately 500 ppm to over
2000 ppm. The higher concentrations generally occur during the winter
months when I am spending more of my time indoors, and am preserving the
heat by running the forced air intake fans less. (This will be changing in
the future, as I will be forcing air from a solar heated porch into the
house during some winter daylight hours)

My question is, from knowing the co2 concentration (and humidity percent
also) in a closed space, how can I calculate the oxygen concentration? I
know that the o2 conentration of normal dry air is around 20.95 percent, but
suspect that the relationship is not perfectly direct between the increase
in co2 and the decrease of 02.

Any help on this math problem would be appreciated.

Thanks
Jim

2000 ppm (parts per million) is 0.2%. The CO2 comes from carbohydrates, amino acids and fats being oxidized (burned) by your cells. So the normal air concentration of oxygen in the air is 20.9%. If 0.2% of the O2 gets reduced to CO2, then the O2 concentration would be 20.7%. (I am ignoring the CO2 concentration in the atmosphere, which is around 0.04% or 400 ppm).

The numbers are an oversimplification, but, in real life, they aren't far off.

In other words, it doesn't change that much. And there is some O2 leaking in and CO2 leaking out through little gaps in the walls, under the doors, etc. No house is 100% airtight.

Jeff
.

Relevant Pages

  • Re: Oxygen percent in a room
    ... a closed room. ... I live in a recently built house that is one of these "super-insulated" ... structures with little outside air exchange except what is forced via fans. ... The measured co2 in my living area ranges from approximately 500 ppm to over ...
    (sci.chem)
  • oxygen concentration in a room
    ... a closed room. ... I live in a recently built house that is one of these "super-insulated" ... structures with little outside air exchange except what is forced via fans. ... The measured co2 in my living area ranges from approximately 500 ppm to over ...
    (sci.med)
  • Oxygen percent in a room
    ... a closed room. ... I live in a recently built house that is one of these "super-insulated" ... structures with little outside air exchange except what is forced via fans. ... The measured co2 in my living area ranges from approximately 500 ppm to over ...
    (sci.chem)
  • Re: Oxygen percent in a room
    ... I live in a recently built house that is one of these "super-insulated" ... The measured co2 in my living area ranges from approximately 500 ppm to ... heat by running the forced air intake fans less. ... from knowing the co2 concentration (and humidity percent ...
    (sci.chem)
  • Re: Oxygen percent in a room
    ... a closed room. ... I live in a recently built house that is one of these "super-insulated" ... structures with little outside air exchange except what is forced via fans. ... The measured co2 in my living area ranges from approximately 500 ppm to over ...
    (sci.chem)