Biological Monitoring

According to the American Conference of Governmental Industrial Hygienists

“Biological monitoring provides one of the means to assess the exposure and health risk to workers. It entails the measurement of the concentration of a chemical determinant in the biological media of those exposed and is an indicator of the uptake of a substance. Biological Exposure Indices (BEIs®) are guidance values for assessing biological monitoring results.”

Presently, ACGIH has set BEIs® for more than 50 substances, including acetone, benzene, cadmium, carbon monoxide, chromium, dichloromethane, lead, mercury, methanol, methyl ethyl ketone, phenol, styrene, toluene, uranium, and xylene. Carbon monoxide is one of only a few of the listed substances in which end-exhaled (alveolar) air is a biological determinant.

For carbon monoxide, the values given are:

Carboxyhemoglobin in blood End of shift 3.5% of hemoglobin
Carbon monoxide in end-exhaled air End of shift 20 ppm

The relationship between alveolar CO and carboxyhemoglobin was first demonstrated by Sjoöstrand in 1948, and had been applied to both smokers and firefighters in 1976. [Find Sjoöstrand citation in “smokers” link.] Several subsequent papers have been published on the measurement of end-exhaled carbon monoxide.

Based on data from the “firefighters” paper [Stewart et al.], Interscan developed a best-fit curve:

This data is also provided in tabular format.

Interscan carbon monoxide analyzers can readily be used to perform measurements of end-exhaled CO. Typically, the patient exhales that portion of his/her breath into a gas sampling bag, and then the bag is connected to the instrument for a CO reading.

Please contact us for further information.

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