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Carbon Monoxide Poisoning

Forklift, lift truck, Hi-Lo Use:

Warehouse Workers' Headache: Carbon monoxide poisoning from propane-fueled forklifts

Fawcett, T.A., Moon, R.E., Fracica, P.J., Mebane, G.Y., Theil, D.R., Piantadosi, C.A.


Journal of Occupational Medicine, 34, pgs. 12-15.

We reviewed over 220 cases of acute carbon monoxide (CO) poisoning and now report on 17 patients whose poisoning occurred from the indoor use of propane-fueled forklifts. All patients in this series presented with neurologic symptoms or persistent headache and were given hyperbaric oxygen to resolve their symptomatology. We investigated the concentrations of CO in the exhaust emissions of 12 propane-fueled forklifts used in various workplaces in our location. The average CO concentration in the exhaust during engine idling was 36,000 parts per million (3.6%). This value decreased slightly to 30,000 ppm (3.0%) at working engine speed. Measurements of exhaust flow indicate CO production rates of approximately 60 liters per minute at working engine speed. These quantities of CO constitute a significant occupational exposure risk to workers using propane-fueled forklifts in unventilated indoor environments.

Location of Authors:
Durham, North Carolina

To Especially Note:

"Analysis of forklift exhaust gases showed significant CO production during idle and working throttle speed. Values at idle varied from 200 - 88,700 ppm, or 0.02% to 8.87%. The average exhaust CO concentration during idle was 3.56% +/-3.31% (S.D.). At working speed the values varied from 0.09% (900 ppm) to 7.28% (72,800 ppm). On the average, engine efficiency improved slightly at working speed, reducing mean CO in the exhaust to 3.05% +/-2.92%. Exhaust flow rates at idle averaged 450 liters/min. and at working speed 2000 liters/min. At this rate of CO production, the average forklift would produce 16 liters of CO per minutes at idle, and 61 liters of CO per minutes at working speed."
"Engine specifications as published by a major propane fuel carburetor manuufacturer indicate that exhaust emissions at idle should produce no less than 1.0% to 1.5% CO for optimum performance. Engine specifications for commonly used forklifts indicate an engine size of 1.8 liters displacement, with an idle speed of 650 r.p.m., and full-throttle setting of 2600 r.p.m. For a four-cycle engine, this results in exhaust flow rates of 585 liters/min at idle and 2340 liters/min. at full throttle."
How would these emissions affect the atmosphere in a closed space? Consider a large warehouse with a volume of 60,000 cubic meters (10 x 60 x 100 m): An average forklift producing 60 liters of CO per minute while working would equilibrate to 1 ppm of CO per minute of operation. With zero ventilation, this workplace could exceed EPA standards for 8-hour exposure in only 9 minutes! This rate of CO production exceeds current automobile exhaust emission standards by 100- to 1000-fold, and, in fact, corresponds to pre-1968 exhaust emission measurments.

...... last changed 07/30/01

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