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• Toxicity of carbon dioxide gas, CO2 exposure limits
• Symptoms of CO2 or carbon dioxide poisoning
• Health effects of carbon dioxide gas exposure
• Recommendations for gas measurement instruments, gas detector tubes, Draeger & Gastec tubes & pumps for detection of gases

This document discusses the toxicity and exposure limits for exposure to carbon dioxide gas (CO₂). We give references and explanation regarding Toxicity of Carbon Dioxide, based on literature search and search on Compuserve's Safety Forum by Dan Friedman. This is background information, obtained from expert sources. This text may assist readers in understanding these topics. However it should by no means be considered complete nor authoritative. Seek prompt advice from your doctor or health/safety experts if you have any reason to be concerned about exposure to toxic gases.

Links on this page also direct the reader to carbon monoxide gas information in a separate document. IF YOU SUSPECT ANY BUILDING GAS-RELATED POISONING GO INTO FRESH AIR IMMEDIATELY and get others out of the building, then call your fire department or emergency services for help. © Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

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.

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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CARBON MONOXIDE - CO
CARBON DIOXIDE - CO₂
  CO₂ POISONING SYMPTOMS
  CO₂ HEALTH EFFECTS
  CO₂ EXPOSURE LIMITS
  TYPICAL CO₂ LEVELS
OXYGEN - O₂
GAS MEASUREMENT TOOLS

• Per Levéen, email comments 23 May 2009 . Mr. Levéen is with Telia, the leading mobile telephone operator in Sverige (Sweden). By telephone Telia (not Mr. Levéen) can be reached at 90 200 or From abroad at +46-771-99 02 00
• Dr. Roy Jensen, Department of Chemistry, Grant MacEwan College, Edmonton, AB for technical review and critique 8/23/07. Dr. Jensen notes that if we increase the CO₂ level in air in an enclosed space from its normal level of about 0.03% (we counted it as starting at 0) to a level of 1.4%, we obtain a corresponding decrease in the oxygen level from its normal level (at sea level) of about 20.9% down to 19.5%, for a 6.7% reduction in the amount of oxygen available. The amount of oxygen lost is 6.7 % (1.4/20.9 * 100 %). Our earlier version of this document was incorrect in this calculation.
• Toxic Gas Exposure Hazards and Test Protocols including links to our toxic gas exposure screening and gas testing protocols.
• "Table Z-1 Limits for Air Contaminants, 1910.1000 Table Z-1" OSHA standard for air contaminant limits (http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9992) - includes for CO2, Carbon dioxide.........| CAS No. 124-38-9 | 5000 ppm | 9000 mg/m3 limits for carbon dioxide as an air contaminant.
• Health Effects of Carbon Dioxide - see "National Advisory Committee for Acute Exposure Guideline Levels (AEGLs) for Hazardous Substances; Proposed AEGL Values, Federal Register Document", http://www.epa.gov/EPA-TOX/2002/February/Day-15/t3774.htm note that these are proposed guidelines

More Information on Building Diagnostic Inspections and Repairs

Gases: Toxic gases, indoor exposure levels, testing, identification

• A Toxic Gas Testing Plan: A Gas Sampling Plan for Residential and Commercial Buildings lists some of the toxic indoor gases for which we test, depending on the building complaint and building conditions
• Gas Exposure Hazard Levels: for Toxic Gas Exposure to Ammonia, Arsine, Arsenic, Bromine, Carbon Dioxide, Carbon Monoxide, Hydride, Ozone - allowable exposure levels and hazard levels
• Carbon Dioxide Gas Toxicity hazard level, poisoning symptoms, & testing
• Carbon Monoxide Gas Toxicity hazard levels, poisoning symptoms, & testing
• Formaldehyde: US EPA. UFFI (Urea Formaldehyde Foam Insulation) was previously considered a hazard (formaldehyde outgassing). Subsequent research virtually closed concern regarding this material; however formaldehyde appears to remain a health concern for sensitive individuals.
• Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
• Sampling for gases in air such as VOC's, MVOC's, toxic chemicals, and combustion products.
  Unfortunately no single test or tool can detect all possible building contaminants. We use methods and equipment which can test for common contaminants. If the identity of a specific contaminant is known in advance we can also test for a very large number of specific contaminant gases in buildings.
  We use gas sampling equipment provided by the two most reliable companies in the world, Draeger-Safety's detector-tubes and Drager accuro� bellows pump, the Gastec� cylinder pump and detector-tube system produced by Gastec or Sensidyne, and we also use Sensidyne's Gilian air pump. For broad screening for combustibles and a number of other toxic gases and for leak tracing we also use Amprobe's Tif8850. All of these instruments, their applications, and sensitivities (minimum detectable limits) for specific gases are described in our Gas Sampling Plan online document.
• Radon Gas U.S. EPA Radon level maps

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