Techniques for reducing exposure to diesel forklift emissions were investigated in two NIOSH studies. In the first study, emissions from filtered and unfiltered diesel forklifts and propane forklifts were compared through measurement of submicrometer elemental carbon (7440440), organic carbon, nitrogen-dioxide (10102440), carbon- monoxide (630080), benzene solubles, polycyclic aromatic hydrocarbons, respirable dust, sulfuric-acid (7664939), sulfates, formaldehyde (50000), acetaldehyde (75070), and acrolein (107028). Questionnaires regarding the presence of exposure symptoms were completed by dockworkers. The filtered and propane engines were associated with a significant reduction in exposure to elemental carbon and in respiratory symptoms. Compared to the filtered engines, the propane engines had significantly higher exhaust concentrations of carbon-monoxide. Personal exposure to nitrogen- dioxide was slightly but significantly reduced through use of ceiling fans; however, concentrations were well below the recommended limit. The authors conclude that use of propane and filtered diesel forklifts significantly reduces particulate exposures and symptom prevalence and that exhaust exposure is not sufficiently reduced by ceiling fans.