Thirty adult, nonsmokers were exposed for four hours to one of three concentrations of carbon monoxide (CO) 5 ppm, 35 ppm, and 70 ppm to produce blood levels of either 1%, 3%, or 5% carboxyhemoglobin (COHb) after the third hour of exposure. Performance in the double blind study was assessed by a tracking task paired with a peripheral monitoring task, each possessing two levels of difficulty. The results indicated that visual-manual tracking was significantly impaired by about 30%, during the fourth hour of exposure to 70 ppm of CO, when 5% COHb was reached, as compared to performance at 5 ppm and 35 ppm. The impairment occurred only during the high frequency tracking condition. Response times of subjects to the peripheral light-intensity-changes also increased during the third and fourth hours. The findings suggested that an assessment of the effects of low-level CO on human performance should include an analysis of the demand characteristics of the tasks as well as data on concentration and exposure duration.; Thirty adult, nonsmokers were exposed for four hours to one of three concentrations of carbon monoxide (CO) 5 ppm, 35 ppm to produce blood levels of either 1%, 3%, or 5% carboxyhemoglobin (COHb) after the third hour of exposure. Performance in the double blind study was assessed by a tracking task paired with a peripheral monitoring task, each possessing two levels of difficulty. The results indicated that visual-manual tracking was significantly impaired by about 30%, during the fourth hour of exposure to 70 ppm of CO, when 5% COHb was reached, as compared to performance at 5 ppm and 35 ppm. The impairment occurred only during the high frequency tracking condition. Response times of subjects to the peripheral light-intensity-changes also increased during th third and fourth hours. The findings suggest that an assessment of the effects of low-level CO on human performance should include an analysis of the demand characteristics of the tasks as well as data on concentration and exposure duration.
