CO2 POISONING SYMPTOMS - Carbon Dioxide poisoning symptoms


The photo shows a Drager colorimetric gas detection tube used to test the CO2 levels in air. In an indoor air test (in our laboratory) the detector found that the CO2 level was about 600ppm which is typical of indoor air and is an acceptable and safe level.

Outdoors the typical carbon dioxide CO2 level in air is 300 ppm to 400 ppm. 400 ppm is a 0.04% concentration of a gas in air.

A comparison with even a relatively low level of indoor CO2 (600 ppm and higher) may indicate a lack of adequate fresh air entering a building.

Basic Information about Concentrations of CO2 in Air

  • 1,000,000 ppm of a gas = 100 % concentration of the gas, and 10,000 ppm of a gas in air = a 1% concentration.
  • At 1% concentration of carbon dioxide CO2 (10,000 parts per million or ppm) and under continuous exposure at that level, such as in an auditorium filled with occupants and poor fresh air ventilation, some occupants are likely to feel drowsy.
  • The concentration of carbon dioxide must be over about 2% (20,000 ppm) before most people are aware of its presence unless the odor of an associated material (auto exhaust or fermenting yeast, for instance) is present at lower concentrations.
  • Above 2%, carbon dioxide may cause a feeling of heaviness in the chest and/or more frequent and deeper respirations.
  • If exposure continues at that level for several hours, minimal "acidosis" (an acid condition of the blood) may occur but more frequently is absent.
  • Breathing rate doubles at 3% CO2 and is four times the normal rate at 5% CO2.
  • Toxic levels of carbon dioxide: at levels above 5%, concentration CO2 is directly toxic. [At lower levels we may be seeing effects of a reduction in the relative amount of oxygen rather than direct toxicity of CO2.]

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 air

What 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 Building

Per 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%)
-0.04 liters of CO2 (0.04%)

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

((1.4/100)*20.9) = 0.29 %.

You displace O2 and N2 for a final composition of:
N2 = (79.1/100)*(100-1.4) = 77.99
O2 = (20.9/100)*(100-1.4) = 20.61
CO2 = 1.4
Total = 100.00

Example of Reduced Oxygen Level in a Building

According 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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