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
