Photograph of a 120Vold carbon monoxide detector device Toxicity of Carbon Monoxide Gas Exposure
Carbon Monoxide CO Gas Exposure Limits PELs & TEVs
     


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Carbon monoxide gas (CO gas) exposure limits: this document lists the standards & limits for exposure to carbon monoxide gas (CO).

We give references and explanation regarding Toxicity of Carbon Monoxide, based on literature search and search on Compuserve's Safety Forum and other authorities including OSHA and NIOSH PEL & TLV gas exposure limit recommendations.

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CO EXPOSURE LIMITS - Carbon monoxide exposure limits PEL and TLV set by OSHA and NIOSH

IF YOU SUSPECT CARBON MONOXIDE POISONING GO INTO FRESH AIR IMMEDIATELY and get others out of the building, then call your fire department or emergency services for help. Links on this page also direct the reader to carbon dioxide gas information in a separate document. Seek prompt advice from your doctor or health/safety experts if you have any reason to be concerned about exposure to toxic gases. Carbon monoxide poisoning can be fatal but exposure at lower limits can produce flu-like symptoms and headaches that are often mistaken for ordinary illness.

Seek prompt advice from your doctor or health/safety experts if you have any reason to be concerned about exposure to toxic gases. Carbon monoxide poisoning can be fatal but exposure at lower limits can produce flu-like symptoms and headaches that are often mistaken for ordinary illness.

Safety Suggestions: Install Carbon Monoxide Detectors in addition to Smoke Detectors

Carbon monoxide detectors are inexpensive and readily available, both as a battery-operated unit and as a unit that plugs into an electrical outlet in the home. No home should be without this safety protection, and homes with gas-fired equipment (natural gas or LP propane), space heaters, or other sources of risk should be extra cautious. Smoke detectors do not protect against carbon monoxide poisoning, and the opposite is also true. Carbon monoxide detectors do not warn of smoke or fire.

Carbon monoxide is a colorless, odorless, tasteless gas that, in its effects on humans, is a chemical asphyxiant - that is, it causes asphyxiation, or death by preventing a person from receiving adequate oxygen. When inhaled, carbon monoxide combines with hemoglobin in the blood more readily than oxygen does. Thus CO "displaces" or moves oxygen out from hemoglobin in the bloodstream. This interferes with oxygen transport by the blood.

A person suffering from carbon monoxide (CO) intoxication may first experience euphoria (similar to the effect of a martini or two), then carbon monoxide poisoning effects lead to a headache, followed by nausea and possibly vomiting as the concentration of carboxyhemoglobin in the blood increases.

To prevent these effects, OSHA has established a PEL of 50 ppm for an 8-hr exposure, identical to the TLV. NIOSH, on the other hand, has decided to be more conservative and recommends a standard of 35 ppm. All of these concentrations refer to exposures with durations of 8 hr/day, 40 hr/week for a working lifetime and all are attempts to establish a "no effect" level.

To prevent these effects, OSHA has established a PEL of 50 ppm for an 8-hr exposure, identical to the TLV. NIOSH, on the other hand, has decided to be more conservative and recommends a standard of 35 ppm.

All of these carbon monoxide or other gas exposure limit concentrations refer to exposures with durations of 8 hr/day, 40 hr/week for a working lifetime and all are attempts to establish a "no effect" level. Here are some other exposure levels and effects of carbon monoxide exposure from various sources:

.

Table I. Effects of Carbon Monoxide Exposure and CO Exposure Limits

PPM CO ExposureEffects of Exposure
to Carbon Monoxide
at this level
Source/comment
0 ppmNo effects, this is the normal level in a properly-operating heating applianceNo carbon monoxide should be detected in residential properties. Possible brief technical exceptions occur.
9 ppmMaximum allowable short term exposureASHRAE
10 - 24 ppmInvestigation needed to find source; Health effects on humans uncertain.
25 ppmMaximum allowable TWA exposure limitOSHA. Used in personal CO alarms.
35 ppmMaximum allowable workplace exposure limit for an 8-hour work shiftNIOSH (40 hour work week)
50 ppmMaximum allowable workplace exposure limit for an 8-hour work shiftOSHA (40 hour work week)
125 ppmWorkplace alarm must soundOSHA
200 ppmEvacuate the area immediately.Exposure at 200 ppm of CO causes dizziness, nausea, fatigue.
400 ppmEvacuate the area.3 hour exposure may be fatal.
800 ppmEvacuate the area.2-3 hour exposure causes convulsions, loss of consciousness, death.
1600 ppmEvacuate the area.
6400 ppmEvacuate the area.30 minutes of exposure causes convulsions, loss of consciousness, death
12,800 ppmEvacuate the area.1-3 minutes of exposure causes convulsions, loss of consciousness, death

NOTES to the Carbon Monoxide Effects Table:

Sources include OSHA, EPA, www.transducertech.com

ABBREVIATIONS: used with gas exposure limits

Definition of PEL = permissible exposure limit. PEL's are a regulatory limitation to exposure used to specify the allowable exposure to a substance in the workplace and assume that the exposure takes place over an 8-hour shift in a 40-hour work week. Note that there are more stringent exposure limits for higher levels of exposure that may occur over a shorter time interval

Definition of PPM = parts per million of concentration of the gas of interest in air. 1 ppm means one part of gas to 1 million parts of air.
See CONVERT PPM to % CONCENTRATION to convert between % and ppm concentration of gases in air

Definition of MAX = maximum exposure in ppm for any individual in the work area over an 8-hour period

Definition of MSDS = Material Safety Data Sheet, published for every chemical or substance that may be hazardous; if an exposure limit has been published for a substance being discussed in an MSDS, that limit, such as TWA or PEL, is required to be included in the MSDS publication.

Ref: 29 CFR 1910.1200 (g)(2)(i)(C)(2) and (g)(2)(vi).

TWA's and PEL's are not available for most chemicals. There are simply too many chemicals, many of which have not gone through the rigorous scientific study and peer review required. The absence of an exposure limit for a substance should not be used to assume that a substance is not hazardous.
See MSDS MATERIAL SAFETY DATA SHEETS

Definition of TIME = as used in environmental exposure literature: the point in time when the maximum exposure will occur from the beginning of any 8-hour period

Definition of TE = total exposure in ppm per hour

Definition of TLV = threshold limit value: the level of exposure that a worker can experience in the workplace without an unreasonable risk of disease or injury. These are not estimates of "level of risk" for different exposure levels nor do they address the different means by which a person may be exposed to a substance.

TLV's are specified by ACGIH, the American Conference of Government Industrial Hygienists. TLV's are guidelines prepared by ACGIH and are solely concerned with health risk. They do not address economic considerations.

TLV's are not regulatory but rather are advisory. (See PEL and TWA which are specified by OSHA).

Definition of TWA = time weighted average exposure level. TWA's are a regulatory exposure limit. The TWA calculation takes into account that exposure level may vary over a time period.

Original document source

This carbon monoxide discussion file originated from a technical expert message board discussion on Carbon Monoxide and later Carbon Dioxide alarms, featuring comments by one of the leading authorities on CO, Jack Peterson, P.E., CIH, Ph.D., in May, 1987. NOTE: Daniel Friedman extracted CO and CO2 sections from that document, edited and added practical and field inspection-based information. Since its original publication this document has been expanded by reference materials from a variety of other sources.

 

Continue reading at HEAT EXCHANGER LEAK ALLOWED or select a topic from the More Reading links shown below.

Or see CONVERT PPM to % CONCENTRATION to convert between % and ppm concentration of gases in air

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CO EXPOSURE LIMITS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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