Toxicity of Carbon Monoxide Gas Exposure
Carbon Monoxide CO Gas Exposure Limits PELs & TEVs

CO EXPOSURE LIMITS - Carbon monoxide gas exposure limits - Carbon monoxide exposure limits PEL and TLV set by OSHA and NIOSH
CARBON MONOXIDE - CO - topic home page
CO ALARM CAUSES - separate article
CARBON MONOXIDE INSPECTION - separate article
CO DETECTOR OPTIONS - separate article
MEDICAL EFFECTS of CO - separate article
POISONING SYMPTOMS - CO - separate article
CARBON MONOXIDE WARNING - separate article
Questions & Answers about the safe limits of exposure to carbon monoxide (CO) and about the effects of CO exposure.
References

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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.

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. Readers of this document should also see HEAT EXCHANGER LEAKS.

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 Exposure	Effects of Exposure to Carbon Monoxide at this level	Source/comment
0 ppm	No effects, this is the normal level in a properly-operating heating appliance	No carbon monoxide should be detected in residential properties. Possible brief technical exceptions occur.
9 ppm	Maximum allowable short term exposure	ASHRAE
10 - 24 ppm	Investigation needed to find source;	Health effects on humans uncertain.
25 ppm	Maximum allowable TWA exposure limit	OSHA. Used in personal CO alarms.
35 ppm	Maximum allowable workplace exposure limit for an 8-hour work shift	NIOSH (40 hour work week)
50 ppm	Maximum allowable workplace exposure limit for an 8-hour work shift	OSHA (40 hour work week)
125 ppm	Workplace alarm must sound	OSHA
200 ppm	Evacuate the area immediately.	Exposure at 200 ppm of CO causes dizziness, nausea, fatigue.
400 ppm	Evacuate the area.	3 hour exposure may be fatal.
800 ppm	Evacuate the area.	2-3 hour exposure causes convulsions, loss of consciousness, death.
1600 ppm	Evacuate the area.
6400 ppm	Evacuate the area.	30 minutes of exposure causes convulsions, loss of consciousness, death
12,800 ppm	Evacuate 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:
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
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
MAX = maximum exposure in ppm for any individual in the work area over an 8-hour period
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.
TIME = point in time when the maximum exposure will occur from the beginning of any 8-hour period
TE = total exposure in ppm per hour
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).
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.

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

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.

Frequently Asked Questions (FAQs) about standards & limits for exposure to CO Carbon Monoxide Gas

Question:

My husband was washing away the paint of a small room with a water pressure machine. Due to the baby on the home he decided to close the door and the window to prevent the baby to frightened. A few minuted later he
came out of the room feeling dizzy, he sat down a smoked a cigarette when he stood up he began walking as if drunk still claiming of dizziness, he immediately fell and was unconscious for more than two hours. Was was the real problem? Was it Carbon Monoxide? - Kelly 10/4/11

Reply:

It could be a CO hazard, and it is certainly worth an immediate inspection of your heating equipment by an expert, including an inspection of the chimney as well as all fuel burning appliances and combustion air.

But one is tempted to suspect something about what he was doing.

FIRST STEP: be SURE you have working CO detectors in appropriate locations and correctly installed, including in bedrooms, baby's room, etc.

Question: what are the effects of Long Term CO poisoning.

Hello~ Could you please direct me to any articles dealing with Long Term CO poisoning.
My daughter was exposed for 3 1/2 years while renting an apt. with extemely faulty furnace ductwork.
The Landlord knew of the leaks ~ did NOTHING, and also gave her a defective CO detector.
Finally the Furnace completely broke down and the repair man said it was a miracle that she hadn't died as it was the worst hookup he had ever seen in 29 years. She has been convalescing for the past 11 months but still is quite lethargic and can't awaken on her own even after 12 hours of sleep.
Thank you for any help you can offer us!
Sincerely,
Vanessa Jordan

Reply:

Sure, Vanessa, please see these two articles

MEDICAL EFFECTS of CO - separate article
POISONING SYMPTOMS - CO - separate article

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Technical Reviewers & References

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

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

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

Original document source

Frequently Asked Questions (FAQs) about standards & limits for exposure to CO Carbon Monoxide Gas

Question:

Reply:

Question: what are the effects of Long Term CO poisoning.

Reply:

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Technical Reviewers & References

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