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• Health effects of chronic or high exposure to carbon dioxide gas
• 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 health effects of exposure to elevated levels of 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.

What are the HEALTH EFFECTS of CO₂ Exposure? - Potential Health Hazards of Toxic Gas Exposure

Hazard evaluation consists of comparing measurements of exposure (or dose) with exposures (doses) known to be safe or known to be hazardous. For the most part, because of biological variation, "no effect" levels are much easier to estimate than are "first effect" or other levels indicative of injury.

Toxic levels of carbon dioxide: According to occupational exposure and controlled atmosphere research into CO₂ toxicology, CO₂ is hazardous via direct toxicity at levels above 5%, concentrations not encountered in nature [except perhaps at or near an active volcano or at water-logged soils]. At these high levels there is risk of death from carbon dioxide poisoning. At lower levels there may health effects and there certainly are complaints of exposure at lower levels.

In the preceding section of this article, at CO₂ POISONING SYMPTOMS we discussed symptoms of carbon dioxide exposure. On specific individuals, the effects of exposure to elevated levels of carbon dioxide (CO₂) vary by individual and with exposure level, and exposure duration, ranging from drowsiness (perhaps at levels over 1000 ppm continuous exposure) to the toxic effects listed just above.

How might CO₂ accumulate at a dangerous level in a residential property?

Carbon dioxide, CO₂, from a small leak is unlikely to be dangerous, as it can be expected to be diluted with fresh air mixing in a building. But there can be exceptions in which carbon dioxide may accumulate and reach higher, even dangerous concentrations indoors.

• Flue gas spillage: in an enclosed gas-fired boiler room with a deficient chimney draft can produce high levels of CO₂. In a case in which there is sufficient combustion air, say from a direct air duct to the gas burner, the system may not be producing more dangerous carbon monoxide (CO), but the heating system may nonetheless spilling flue gases with a high level of CO₂ into the room from a defective chimney. Since CO₂ being more dense than air it may accumulate in an enclosed basement, crawl space, or boiler room. Alternatively, because the CO₂ in this case is a heating system exhaust, it may be warmer than surrounding air and it may rise upwards in the building into the living space. For this reason when we measure for the presence of flue gases, even if the gas is one which is "supposed to be" heavier than air, we may measure both high and low in the test area.
• Soil sources of high carbon dioxide in buildings: NIOSH reports on an investigation of complaints by homeowners of blurred vision, breathlessness, and "episodic mild confusion" caused by exposure to from elevated carbon dioxide levels in a finished basement and an adjacent crawlspace. West Virginia Department of Environmental Protection detected carbon dioxide levels up to 9.5 percent in the basement and CO₂levels up to 11 percent in the crawlspace grave, with 12 percent in the basement floor drain (suggesting a soil source of CO₂ in a home in West Virginia home, according to a NIOSH report. CO₂ levels in the soil surrounding the home were measured at levels up to 8 percent. The probable source of the high CO₂ levels in the soils under and around this home were probably due to [coal] mining activities.

Are the effects of breathing CO₂ permanent?

Any detrimental effects of low-level CO₂ exposure are reversible, including the long-term metabolic compensation required by chronic exposure to 3% CO₂. -- "A Review of Human Health and Ecological Risks due to CO₂ Exposure," American Geophysical Union, Spring Meeting 2001, abstract #H31C-13, Hepple, R. P.; Benson, S. M., 05/2001.

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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

• "Gases: Toxic gases, indoor exposure levels, testing, identification" additional information on gas exposure detection, toxicity, and remedy for a wide range of toxic and other gases.
• 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.

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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