OPN 148 - Carbon Monoxide Exposure Documentation Guidelines

This OPN provides guidance on the use of the Coburn Equation to theoretically derive an employee's exposure to carbon monoxide (CO) using their post-exposure blood carboxyhemoglobin (COHb) levels. Under 29 CFR 1910.1000—Air Contaminants and 29 CFR 1926.55—Gases, Vapors, Fumes, Dusts and Mists, the permissible exposure limit (PEL) for CO is 50 parts per million (ppm) over an 8 hour TWA. 

Also reference the safety and health topic page for Carbon Monoxide and FOM Chapter 03 - Inspection Procedures.