Contact the SLTC Physical Measurements Team Leader in cases where CO poisoning affects more than 4 individuals. The most practical use of resources sometimes requires evaluating the most severely affected employees.

2-5 L

0.01-0.05 L/min

2-5 L

0.3 L/min

If nitric oxide (NO) is present at the monitoring site, please notify the OTC when requesting a monitoring kit and each provided gas monitor will be equipped with both CO and NO sensors. Do not use this method when hydrogen, acetylene, or ethene are present.

Use detector tubes for screening. If greater than PEL, order gas sampling bags.

*Note for sampling with Cali-5-BondTM, 10 liter, five layer aluminized gas sampling bag: This gas sampling bag has an integrated twist on/off valve (V-NPB-2/00) Septum (A-SEPT/.750). The nickel-plated brass connection allows the user to control gas flow into or out of the bag by twisting the barbed stem open (counterclockwise) or closed (clockwise). The jagged barb firmly secures 3/16″ ID sample tubing to the stem of the valve.

COHb analysis is a routine measurement during the medical response to a suspected CO-poisoning incident or from an autopsy after a suspected CO-poisoning incident. As a result, the COHb analysis is performed using a blood-gas instrument that is part of a quality system. The COHb analysis is not performed at the SLTC.

Carbon monoxide (CO) exposure is determined by calculation based on carboxyhemoglobin (COHb) measurements provided by medical professionals as described below. OSHA uses a modified Coburn, Forster, Kane (CFK) Calculation. The documented SLTC modifications (printed in the supplemental report that accompanies the results) use a more accurate version of the CFK equation than the closed-form [e.g., ppm CO = f(x,y,z,...)] version used in the 1972 NIOSH criteria document for the purpose of calculating the 8-hr TWA ppm REL that would result in a 5% COHb level [U.S. Department of Health, Education, and Welfare: Criteria for a Recommended Standard - Occupational Exposure to Carbon Monoxide. Pub. No. HSM 73-11000. NIOSH, Cincinnati, OH (1972).]

The calculation also provides an incident-specific sampling and analytical error (SAE) based on a Monte-Carlo approach designed to deal with the uncertainties in the data. The calculation is performed at the SLTC and the results are critically assessed for correctness by the SLTC experts prior to reporting. The SLTC is available to assist the CSHO with acquiring the data and interpreting the results.

The exposure incident is documented on a worksheet. Personal information is used to assess the affect of any tobacco smoking behavior (before, during and after the exposure), blood volume, and activity levels (during and after the exposure). Post-exposure delay to sampling is preferable less than approx 6 hours for living persons. Longer delays may result in significantly higher SAEs or the inability to distinguish an overexposure from baseline for an individual. Contact Scott Jones at 801-233-4962 [OSHA staff only].

For further information please enroll in the Carboxyhemoglobin (COHb) training resource in course mill “TR_CO Calculated from Carboxyhemoglobin”.