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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 exposure limits for 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 2010 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 Allowable Limits of CO₂ EXPOSURE - Carbon dioxide exposure limits PEL and TLV set by OSHA and NIOSH

Carbon dioxide is regulated for diverse purposes but not as a toxic substance.

• The U.S. EPA CO₂ exposure limits: The U.S. EPA recommends a maximum concentration of Carbon dioxide CO₂ of 1000 ppm (0.1%) for continuous exposure.
• ASHRAE standard 62-1989 recommends an indoor air ventilation standard of 20 cfm per person of outdoor air or a CO₂ level which is below 1000ppm.
• NIOSH CO₂ exposure limits: NIOSH recommends a maximum concentration of carbon dioxide of 10,000 ppm or 1% (for the workplace, for a 10-hr work shift with a ceiling of 3.0% or 30,000 ppm for any 10-minute period). These are the highest threshold limit value (TLV) and permissible exposure limit (PEL) assigned to any material.
• OSHA CO₂ exposure limits: OSHA recommends a lowest oxygen concentration of 19.5% in the work place for a full work-shift exposure. As we calculated above, for the indoor workplace oxygen level to reach 19.5% (down from its normal 20.9% oxygen level in outdoor air) by displacement of oxygen by CO₂, that is, to reduce the oxygen level by about 6%, the CO₂ or carbon dioxide level would have to increase to about 1.4% 14,000 ppm.

In summary, OSHA, NIOSH, and ACGIH occupational exposure standards are 0.5% CO₂ (5,000 ppm) averaged over a 40 hour week, 3% (3,000 ppm) average for a short-term (15 minute) exposure [we discuss and define "short term exposure limits" STEL below], and 4% (40,000 ppm) as the maximum instantaneous limit considered immediately dangerous to life and health. All three of these exposure limit conditions must be satisfied, always and together.

What laws regulate carbon dioxide exposure levels?

Of the several industrial hygiene standards-setting groups in this country, the most important and/or most quoted are the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA), and the American Conference of Governmental Industrial Hygienists (ACGIH) but these are recommended standards, not laws.

Standards promulgated by OSHA (called Permissible Exposure Limits or PELs) have the force of law. The other standards are advisory. However OSHA claims the power to force compliance with NIOSH "Recommended Standards" if it chooses to do so. (The main advantage of ACGIH Threshold Limit Values (TLVs) is that they are reviewed and updated annually; neither NIOSH nor OSHA updates its standards with any regular frequency.)

NIOSH limits on Carbon Dioxide Exposure: NIOSH's recommended CO₂ exposure limit for 15 minutes is 3 percent. A CO₂ level of 4 percent is designated by NIOSH as immediately dangerous to life or health.

OSHA limits on Carbon Dioxide Exposure: The U.S. Department of Labor Occupational Safety & Health Administration, OSHA, has set Permissible Exposure Limits for Carbon Dioxide in workplace atmospheres at 10,000 ppm of CO₂ measured as a Time Weighted Average (TWA) level of exposure and OSHA has set 30,000 ppm of CO₂ as a Short-Term Exposure Limit (STEL). OSHA has also set a Transitional Limit of 5,000 ppm CO₂ exposure TWA. [OSHA's former limit for carbon dioxide was 5000 ppm as an 8-hour TWA.]

Definitions of Short Term Exposure Limits or STEL

What is the definition of "short term exposure" or "Short-Term Exposure Limit (STEL)"? The ACGIH has defined STEL as the concentration (in this case of a gas in air) to which workers can be exposed continuously for a short period of time without suffering from irritation, chronic or irreversible tissue damage, or narcosis of sufficient degree to increase the likelihood of accidental injury, impair self-rescue or materially reduce work efficiency.

What is a "short period"? and what is "short term exposure"?: The definition of "short period" is provided indirectly by ACGIH:

1. If during an 8-hour work shift (and before it has ended) a worker is exposed to a substance in excess of the threshold limit value, time weighted average exposure permitted exposure level for the entire shift, then that exposure has exceeded the short term exposure limit or STEL.
2. If a worker is exposed to more than four STEL periods during the course of an 8-hour work shift, with less than 60 minutes between those exposure periods, then also that exposure has exceeded the STEL.

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

• 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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