Abstract
The Colorado Department of Public Health and Environment (CDPHE) measured area carbon monoxide concentrations at three separate workplaces where workers had experienced acute carbon monoxide poisoning related to the indoor use of propane-fueled fork-lifts. Follow-up investigations were conducted at two of these workplaces where full-shift carbon monoxide exposure and end-exhaled carbon monoxide concentrations were measured to estimate carboxyhemoglobin concentrations. Draeger dataloggers equipped with carbon monoxide sensors were used to measure full-shift personal exposure and area airborne carbon monoxide concentrations. The dataloggers were also used to measure preshift and postshift end-exhaled carbon monoxide concentrations, which were then used to calculate carboxyhemoglobin concentrations. At the first workplace, a beverage distributing warehouse using two propane-fueled Nissan forklifts, carbon monoxide exposures ranged from 25 to 68 ppm (mean = 44 ppm) as work shift time-weighted averages (TWAs), with peaks ranging from 43 to 639 ppm. The range of increase in end-exhaled carbon monoxide concentrations of the tested nonsmoking employees was 17 to 65 ppm (average increase was 42 ppm) through the work shift. Following forklift maintenance and a reduction in the use of forklifts, employee exposures were reduced (range of TWAs was 16 to 33 ppm; mean = 25 ppm), but were still in excess of recommended limits. The range of increase in end-exhaled carbon monoxide concentrations for nonsmokers after maintenance was 13 to 40 ppm (average increase was 26 ppm), again indicating that maintenance was not adequate. At the second workplace, a sugar packaging company also using two propane-fueled Nissan forklifts, carbon monoxide exposures measured after forklift repairs and related reduction in carbon monoxide emissions were low (1 to 10 ppm over a 7-hour work shift). The increases in end-exhaled carbon monoxide concentrations for the two nonsmokers at this workplace were 2 and 3 ppm. Area concentrations of carbon monoxide measured at the third workplace were as high as 300 ppm. The data from these workplaces combined with data related to 57 other propane-fueled forklift-related carbon monoxide poisoning cases found through CDPHE record reviews and literature searches demonstrate that the use of propane forklifts indoors without diligent monitoring of carbon monoxide emissions, and without subsequent maintenance aimed at reducing these emissions, can result in carbon monoxide poisoning.
