> How much carbon dioxide is there in non-urban and indoor air?
How much carbon dioxide is there in non-urban and indoor air?
Measurements of carbon dioxide are usually made in very
clean locations like a mountain top or the South Pole. At
present (1998) the values range between 360 and 375 parts of
carbon dioxide per million parts of air depending on the
hemisphere (the northern is higher) and the season (the
biological growing season is lower). One can try to extrapolate
these background concentration numbers to the locations you ask
about but they represent one's best guess.
In the suburbs of big cities, but outdoors, the
concentration might be between 360 parts per million as a likely
lower value (except in summer near growing plants or trees where
it might be 10 or 20 units lower) to high values of 750 parts of
carbon dioxide to a million parts of air. In very isolated
places immediately downwind of the burning of coal or gasoline
(heavy traffic) the values might even be double those just
quoted.
In buildings the carbon dioxide concentration depends mainly
on how many people have been inside the area of the building, its
volume and whether or not there has been any leakage from the
burning of oil, coal or natural gas in the house. Thus, the
concentrations can be extremely variable. I believe that I saw
numbers obtained in schoolrooms where there were the usual number
of children and the values of concentration were as high as 4,000
parts of carbon dioxide per million parts of air. People use
oxygen and breathe out carbon dioxide. I would guess that a more
typical value in an average home is about twice that out of doors
or about 750 parts of carbon dioxide per million parts of air.
You can appreciate that the estimates of suburban outdoor
air and that in buildings are mine and if these numbers are to be
used in important decisions much more research should be
conducted to get more certain values. I would predict, however,
that any study would exhibit very variable concentrations that
might not be too helpful.
