Abstract: On February 19, 1992, Employees #1 and #2 were assigned by their employer to cut out a lally column from a poured concrete foundation in the basement of a private residence. The basement had two covered windows, no source of external ventilation, and could only be accessed from the first floor. Cutting started at 8:45 a.m. and proceeded for 15 to 20 minutes before a 15 minute break was taken outside. The cutting was resumed by Employee #1 until he fell unconscious at 10:30. An ambulance arrived at 10:32 and EMTs administered oxygen. At 10:45, Employee #1 was transported to the hospital, where he was placed in triage at 11:30. A blood sample was taken at 1:01 p.m. and analyzed at 1:21 p.m. Both Employees #1 and #2 were evaluated and released. Employee #1 had suffered carbon monoxide poisoning. Employee #2 was asymptomatic; therefore, no blood sample was taken.