Basic Information about Concentrations of CO2 in Air
Symptoms of high or prolonged exposure to carbon dioxide include headache, increased heart rate, dizziness, fatigue, rapid breathing, visual and hearing dysfunctions. Exposure to higher levels may cause unconsciousness or death within minutes of exposure. Distinguishing between high carbon dioxide levels CO2 and low oxygen levels O2 in airWhat may be unclear in some cases is whether the sub-acute (sub-toxic) effects at modestly-elevated levels of CO2 in air stem from more from exposure to higher levels of carbon dioxide or whether they are due to reduced levels of oxygen. In an enclosed space such as a tight home or an enclosed basement or work space, increasing the level of CO2 is likely to simultaneously reduce the proportion of Oxygen (O2) in that same breathing air. Some experts opine that complaints that seem to be associated with high CO2 problem in many if not most circumstances are likely to be actually due to the corresponding reduction in available oxygen in air rather than high toxicity levels of CO2 in the air. As carbon dioxide levels climb above a few percent the relative proportions of gases making up that air change: the concentration of oxygen in the air inhaled is reduced as the amount of CO2 is increased. Example of Fatal Levels of CO2 Carbon Dioxide in a BuildingPer Levéen has thoughtfully provided the detailed analysis comparing the hazards of elevated carbon dioxide in a building with the accompanying reduction of O - oxygen in the same space as the level of CO2 increased. 100 liters of air contains: -20.9 liters of oxygen (20.9%) If we add 1.4 liters of CO2 to this mixture, we will get 101.4 liters of air with: (1.4 + 0.04) / 101.4 = 0.014 = 1.4 % CO2 and 20.9 / 101.4 = 0.206 = 20.6 % oxygen This change in the mix of gases in air when the level of CO2 increased results in a decrease with 1.4% in the oxygen level (and not 6.7% as is stated at Example of Reduced Oxygen Level in a Building) This is important because we recently had an accident with CO2 in Sweden killing two persons. According to the newspapers CO2 is nontoxic and it is the decreased oxygen levels that kills. Using the equation above one can quickly conclude that adding 31 liters of CO2 would result in 24% CO2(almost instantly fatal) and 16% oxygen (equivalent with breathing at 2800 meters above sea level, which is not dangerous). In conclusion, it is the toxic properties of CO2 that is fatal, not the drop in oxygen. According to the calculation shown below at Example of Reduced Oxygen Level in a Building, a level of 1.4% CO2 cause a drop of oxygen from 20.9% to 19.5%. As the arithmetic above shows, This calculation is misleading. Saying that adding 1.4% CO2 causes oxygen to drop to 20.9 - 1.4 = 19.5% is like saying that adding 20.9% CO2 would cause oxygen to drop to 20.9 - 20.9 = 0% That is of course not true. The correct and more precise calculation is provided above this paragraph. The analysis above gives a reduction on 6.7% of O2 for a CO2 value of 1.4% ( (1.4/20.9)*100) =.6.7.%. KC Baczewski PE writes that this should be
Example of Reduced Oxygen Level in a BuildingAccording to Example of Fatal levels of CO2 Carbon Dioxide in a Building (above), the math of the following example is not quite correct. We have kept Dr. Jensen's comments (below) but they should be read together with the detailed example and calculation provided above by Per Levéen. More carbon dioxide may mean less oxygen: Let's say, sake of simplicity, that we're converting oxygen to carbon dioxide in an enclosed space. Then when the CO2 level has increased from its normal amount in air (about 0.03%) up to a higher concentration in air of 1.4% CO2 the concentration of oxygen in air will have decreased from 20.9 to 19.5%. Reducing the oxygen concentration from 20.9% down to 19.5% is equal to a 6.7% reduction in the oxygen level. -- Thanks to thanks to Dr. Roy Jensen for assistance with these details. What are the effects on humans (and other animals) of reduction of the oxygen levels in air? At sea level, breathing air in which the O2 level has fallen to 16% percent is equivalent to being at the top of a 9,200-foot mountain - close to the level at which many people will experience shortness of breath while walking. 12% Oxygen in air at sea level corresponds to breathing normal air at an elevation of about 17,400 feet.
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