A. In an average, healthy individual, 1% or less of the total hemoglobin is complexed as COHb

B. Since CO is a product of tobacco smoke, many smokers have COHb levels in the range of 3% to 8% of total hemoglobin, and the levels can rise to 15% for chain-smokers

C. COHb levels equilibrate at 50% in people who breathe air containing 570 ppm of CO for several hours

D. Because of their higher base levels of COHb, smokers exposed to a source of CO often develop symptoms slower than nonsmokers