WHAT IS CARBON MONOXIDE?

Carbon monoxide enters the bloodstream through the lungs and forms carboxyhemoglobin, a compound that inhibits the blood's capacity to carry oxygen to organs and tissues. Persons with heart disease are especially sensitive to carbon monoxide poisoning and may experience chest pain if they breathe the gas while exercising. Infants, elderly persons, and individuals with respiratory diseases are also particularly sensitive. Carbon monoxide can affect healthy individuals, impairing exercise capacity, visual perception, manual dexterity, learning functions, and ability to perform complex tasks.

Carbon monoxide (CO) is a colorless, odorless, poisonous gas. A product of incomplete burning of hydrocarbon-based fuels, Natural Gas, Oil, Coal, Wood, Kerosene, etc. carbon monoxide consists of a carbon atom and an oxygen atom linked together.

Carbon Monoxide is the leading cause of accidental poisoning deaths in America, according to the Journal of the American Medical Association (JAMA). 1,500 people die annually due to accidental carbon monoxide exposure, and additional 10,000 seek medical attention.. (Medical experts agree that it's difficult to estimate the total number of carbon monoxide incidents because the symptoms of carbon monoxide poisoning resemble so many other common ailments.)

How is Carbon Monoxide Formed?

Carbon monoxide results from incomplete combustion of fuel and is emitted directly from vehicle tailpipes. Incomplete combustion is most likely to occur at low air-to-fuel ratios in the engine. These conditions are common during vehicle starting when air supply is restricted ("choked"), when cars are not tuned properly, and at altitude, where "thin" air effectively reduces the amount of oxygen available for combustion (except in cars that are designed or adjusted to compensate for altitude).

Nationwide, two-thirds of the carbon monoxide emissions come from transportation sources, with the largest contribution coming from highway motor vehicles. In urban areas, the motor vehicle contribution to carbon monoxide pollution can exceed 90 percent.

During normal combustion, each atom of carbon in the burning fuel joins with two atoms of oxygen -forming a harmless gas called carbon dioxide. When there is a lack of oxygen to ensure complete combustion of the fuel, each atom of carbon links up with only one atom of oxygen - forming carbon monoxide gas.

Incompatibilities: Contact of carbon monoxide with strong oxidizing agents, or halogen compounds causes a violent reaction.

EXPOSURE LIMITS

In 1992, carbon monoxide levels exceeded the Federal air quality standard in 20 U.S. cities, home to more than 14 million people.

* OSHA PEL The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for carbon monoxide is 50 parts per million (ppm) parts of air (55 milligrams per cubic meter (mg/m(3))) as an 8-hour time-weighted average (TWA) concentration [29 CFR Table Z-1].

* NIOSH REL The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for carbon monoxide of ppm (40 ()mg/m(3)) as an 8-hour TWA and 200 ppm (229 mg/m(3)) as a ceiling [NIOSH 1992].

* ACGIH TLV The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned carbon monoxide a threshold limit value (TLV) of 25 ppm mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 15].

What is the danger to me?

Carbon monoxide inhibits the blood's capacity to carry oxygen. In our lungs, CO quickly passes into our bloodstream and attaches itself to hemoglobin (oxygen carrying pigment in red blood cells). Hemoglobin readily accepts carbon monoxide - even over the life giving oxygen atoms (as much as 200 times as readily as oxygen) forming a toxic compound known as carboxyhemoglobin (COHb).

By replacing oxygen with carbon monoxide in our blood, our bodies poison themselves by cutting off the needed oxygen to our organs and cells, causing various amounts of damage - depending on exposure.

Low levels of carbon monoxide poisoning (with COHb levels of 10%) result in symptoms commonly mistaken for common flu and cold symptoms - shortness of breath on mild exertion, mild headaches, nausea.

With higher levels of poisoning (COHb levels of 30%) the symptoms become more severe - dizziness, mental confusion, severe headaches, nausea, fainting on mild exertion.

At high levels (CHOb of 50% or more) there may be unconsciousness and death.

How is it Monitored?

Biological monitoring

Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. A readily available biological monitoring method for carbon monoxide involves the measurement of carboxyhemoglobin concentration in the blood by means of automated visible spectrophotometry. The recommended maximum allowable carboxyhemoglobin level for workers is 5 percent, which corresponds to an 8-hour exposure of 35 ppm. Exposure at the current PEL of 50 ppm for 8 hours will yield a carboxyhemoglobin level of 8 to 10 percent in most workers.

A pre-exposure sample should be taken and analyzed to determine background carboxyhemoglobin levels resulting from smoking, various diseases, and non-occupational exposures. It is especially important that smokers and non-smokers be measured separately; the carboxyhemoglobin levels in smokers range from 3 to 10 percent and may be as high as 20 percent in cigar smokers.

The following table describes the symptoms associated with a given concentration of COHb:

% COHb Symptoms and Medical Consequences

10%               No symptoms. Heavy smokers can have as much as 9% COHb.

15%               Mild headache.

25%               Nausea and serious headache. Fairly quick recovery after treatment with oxygen and/or fresh air.

30%               Symptoms intensify. Potential for long term effects especially in the case of infants, children, the elderly, victims of                       heart disease and pregnant women.

45%               Unconsciousness.

50%+             Death.

WORKPLACE MONITORING AND MEASUREMENT

Neither NIOSH nor OSHA has a recommended method for full-shift sampling of employee exposure to carbon monoxide in the workplace. However, the following analytical methods are available.

Determination of a worker's exposure to airborne carbon monoxide is made using an Ecolyzer direct reading field instrument. This instrument is capable of detecting carbon monoxide concentrations between 0 and 600 ppm. Several types of detector tubes are available to screen for the presence of carbon monoxide; these tubes have a reported limit of detection of 0.5 ppm. This equipment and the ranges of carbon monoxide detection are described in the OSHA Computerized Information System [OSHA 1994].

Since one can't easily measure COHb levels outside of a medical environment, CO toxicity levels are usually expressed in airborne concentration levels (PPM) and duration of exposure. Expressed in this way, symptoms of exposure can be stated as follows:

PPM CO               Time                  Symptoms

35 PPM              8 hours            Maximum exposure allowed by OSHA in the workplace over an eight hour period
200 PPM            2-3 hours        Mild headache, fatigue, nausea and dizziness.
400 PPM            1-2 hours        Serious headache- other symptoms intensify. Life threatening after 3 hours.
800 PPM            45 minutes       Dizziness, nausea and convulsions. Unconscious within 2 hours. Death within 2-3 hours.
1600 PPM          20 minutes       Headache, dizziness and nausea. Death within 1 hour.
3200 PPM          5-10 minutes   Headache, dizziness and nausea. Death within 1 hour.
6400 PPM          1-2 minutes     Headache, dizziness and nausea. Death within 25-30 minutes.
12,800 PPM       1-3 minutes     Death.

As can be seen from the above information, the symptoms vary widely based on exposure level, duration and the general health and age on an individual. Also note the one recurrent theme that is most significant in the recognition of carbon monoxide poisoning- headache, dizziness and nausea. These 'flu like' symptoms are often mistaken for a real case of the flu and can result in delayed or misdiagnosed treatment. When experienced in conjunction with a the sounding of a carbon monoxide these symptoms are the best indicator that a potentially serious buildup of carbon monoxide exists. This comment will be returned to later.

Atmospheric         COHb in
CO (ppm)             Blood (%)         Symptoms

     70                       10                  Shortness of breath upon vigorous exertion; possible tightness across the forehead.
    120                      20                  Shortness of breath with moderate exertion;
                                                      occasional headache with throbbing in the temples.
    220                      30                  Decided headache; irritability; easy fatiguability; disturbed judgment;
                                                      possible dizziness; dimness of vision.
 350-520               40-50               Headache; confusion; collapse; fainting upon exertion.
 800-1220             60-70               Unconsciousness; intermittent convulsions;
                                                      respiratory failure; death if exposure is prolonged.
    1950                     80                 Rapidly fatal.

Adults (non-smokers) normally have about 1% COHb in the body. Cigarette smokers generally have blood levels of 2 to 10% COHb (5.20.).

Carbon Monoxide Action Levels

Standard for Action Levels

The following action levels have been defined as minimums for BPI certified Carbon Monoxide Analysts. Analysts may work for a government agency or business entity that has adopted more stringent standards than the ones defined in this document. As such, CO Analysts may enforce those higher standards. Under no circumstances shall a BPI certified CO Analyst recognize less stringent standards or ignore conditions in excess of the defined action levels. The action levels are considered net indoor ambient readings - i.e. - indoor ambient minus outdoor ambient readings.