Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair

Ask a Question or Search InspectAPedia

• HOME
• AIR CONDITIONING
• ELECTRICAL
• EXTERIORS
• HEATING
• HOME INSPECTION
• INTERIORS
• PLUMBING
• ROOFING
• SEPTIC SYSTEMS
• STRUCTURE
• WATER SUPPLY

• ENERGY SAVINGS
• ENVIRONMENT
• INDOOR AIR IAQ
• INSULATION
• MOLD INSPECT TEST REMOVE
• NOISE
• ODORS
• SOLAR ENERGY
• VENTILATION
• EXPERTS DIRECTORY
• CONTACT US

Carbon Dioxide CO₂ Exposure Limits & Toxicity to humans: 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.

Original content, since extensively edited and expanded, was 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 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this 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.

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.

Questions & Answers regarding this article

Questions & answers about Carbon Dioxide CO2 gas exposure limits and toxicity for humans.

Share this Article      

...

Technical Reviewers & References

• InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.
• Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
• Thanks to remaining contributors/references who are listed just below

Use links just below or 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.

CARBON DIOXIDE - CO2
  CO₂ POISONING SYMPTOMS
  CO₂ HEALTH EFFECTS
  CO₂ EXPOSURE LIMITS
  TYPICAL CO₂ LEVELS

• 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.
• GASES, EXPOSURE, TESTING 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
• Klemens C. Baczewski PE, email correspondence, 4/29/2009 discussed correct CO2 calculations.
• Taylor, Lewis G. and G. Oscar Kreutziger, The Gaseous Environment of the Chick Embryo in Relation to Its Development and Hatchability, 1968 (printout does not include the Journal)
• Holloway and Heath, 1984 Ventilatory Changes in the Golden Hamster..., Laboratory Rat...., Comp. Biochem. Physiol., Vol. 77A, No 2, pp. 267-273
• Bruggeman et al. 2007 Acid-base balance in chicken embryois...incubated under high CO₂ concentrations... Respiratory Physiology and Neurobiology 159:147-154
• De Smit et al, 2006 Emryonic developmental plasticity of the chick: Increased CO₂ ... Comparative Biochemistry and Physiology, Part A 145: 166-175
• Bar-Ilan, Amir and Jacob Marder, Adaptations to Hypercapnic conditions in the Nutria..., Comp. Biochem. Physiol. Vol 75A, No 4, pp 603-608, 1983

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.

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
• CCSP, 2008: Analyses of the effects of global change on human health and welfare and human systems. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. [Gamble, J.L. (ed.), K.L. Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)]. U.S. Environmental Protection Agency, Washington, DC, USA. Web search 08/28/2010, original source: http://nepis.epa.gov/
• 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
• 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
• Carbon Dioxide CO2: Geologic Sequestration Health Effects: "Vulnerability Evaluation Framework
  for Geologic Sequestration of Carbon Dioxide", US EPA, EPA430-R-08-009, July 2008, web search August 2010,original source: http://www.epa.gov/climatechange/emissions/downloads/VEF-Technical_Document_072408.pdf
• Carbon Dioxide CO₂: Geologic Sequestration, U.S EPA, web search 08/28/2010, original source:
  http://www.epa.gov/climatechange/emissions/co2_gs_tech.html
  • GTSP, 2006: Carbon Dioxide Capture and Geologic Storage: A Core Element of a A Global
    Energy Technology Strategy to Address Climate Change (PDF, 37 pp., 6.05 MB, About PDF).
    April 2006, JJ Dooley et al. Global Energy Technology Strategy Program (GSTP)
  • IPCC, 2005: Special Report on Carbon Dioxide Capture and Storage, Special Report of the
    Intergovernmental Panel on Climate Change [Metz, Bert, Davidson, Ogunlade,
    de Coninck, Heleen, Loos, Manuela, and Meyer, Leo (Eds.)]. Cambridge University Press, The
    Edinburgh Building Shaftesbury Road, Cambridge CB2 2RU England
    
• Carbon Monoxide Gas Toxicity hazard levels, poisoning symptoms, & testing
• Fluorine, Its Compounds, and Air Pollution,: a Bibliography with Abstracts, US Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina 27711, December 1976. Web search 08/28/2010, original source: http://nepis.epa.gov.
  NOTE: because the EPA's original source of this document in PDF format is damaged we have created a text image file, converted to a new PDF for readability.
• 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.
• Greenhouse Gas Overview: Carbon Dioxide: U.S. EPA, web search 08/28/2010, original source:
  http://www.epa.gov/climatechange/emissions/co2.html
• Nitrogen Oxides: Air Quality Criteria for Oxides of Nitrogen, Vol III of III, US EPA, EPA600/8-91/049cF, August 1993, web search 08/28/2010, original source: http://nepis.epa.gov [Large PDF 25MB]
  Key chapters in this document evaluate the latest scientific data on (a) health effects of NOx measured ill laboratory animals and exposed human populatIOns and (b) effects of NOx on agricultural crops, forests, and ecosystems, as well as (c) NOx effects on visibility and nonbiological materials. Other chapters describe the nature, sources, distribution, measurement, and concentratiOns of NOx m the environment These chapters were prepared and peer reviwed by experts from various state and Federal government offices, academia, and private industry for use by EPA to support decision makIng regarding potentIal risks to public health and the enVIronment Although the document IS not intended to be an exhaustIve literature reVIew, It IS intended to cover all the pertinent literature through early 1993
• 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.
• Sulfur dioxide & other Oxides: Air Quality Criteria for Particulate Matter and Sulfur Oxides, Vol. III, US EPA, Environmental Criteria and Assessment Office, Research Triangle Park NC 27711, Dec. 1982, EPA-600/8/2-029c. Web search 08/26/2010, original source: http://nepis.epa.gov [large PDF]
• Radon Gas U.S. EPA Radon level maps, web search 2005, original source: http://www.epa.gov/iaq/radon/zonemap/zmapp33.htm
• "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.
• GASES, EXPOSURE, TESTING Toxic Gas Exposure Hazards and Test Protocols including links to our toxic gas exposure screening and gas testing protocols.
• ...