The mapping of fine and ultrafine particle concentrations in an engine machining and assembly facility

Aerosol mapping was used to assess particle number and mass concentration in an engine machining and assembly facility in the winter and spring. Number and mass concentration maps were constructed from data collected with two mobile sampling carts, each equipped with a condensation particle counter (10 nm < diameter < 1 microm) and an optical particle counter (300 nm < diameter < 20 microm). Number concentrations inside the facility ranged from 15 to 150 times greater than that outside the facility and were highly dependent on season. The greatest number concentration (>1,000,000 particles cm(-3)) occurred in winter in an area where mass concentration was low (<0.10 mg m(-3)). The increased number of particles was attributed to the exhaust of direct-fire, natural-gas burners used to heat the supply air. The greatest mass concentrations were found around metalworking operations that were poorly enclosed. The larger particles that dominated particle mass in this area were accompanied by ultrafine particles, probably generated through evaporation and subsequent condensation of metalworking fluid components. Repeat mapping events demonstrated that these ultrafine particles persist in workplace air over long time periods.