The incidence of workplace poisonings with carbon-monoxide (630080) related to the indoor use of gas powered equipment was investigated in Colorado. Cases of fatal and nonfatal occupational carbon- monoxide poisoning due to gas powered motors were identified from the population based surveillance system operating in Colorado. From 1985 through September of 1994, there were 2,343 unintentional carbon-monoxide poisonings reported to the surveillance system. Of these, 349 were work related. There were 24 deaths among these work related poisonings, 14 of whom were firefighters who died in a forest fire. Gas powered engines accounted for the largest number of cases, 139 out of 349 or 40%. The gas powered engines included smaller engines such as those found in forklifts, construction equipment, and cleaning equipment. Of the gas powered engines, concrete saws were the most frequent source of poisoning, 29 cases. Ninety six percent of all poisonings from gas powered engines occurred indoors or in an enclosed space. The most frequent symptoms included headache, nausea and dizziness. When the carboxyhemoglobin (COHb) levels were plotted against the duration of exposure, the concrete saw operators had higher COHb levels with shorter exposure durations than did the operators of other gas powered equipment. The authors conclude that the use of gas powered equipment indoors or in an enclosed space is hazardous and should be avoided except in emergency situations.