Oil mist concentration: A comparison of sampling methods

Discrepancies arise when sampling mineral oil mist using a glass fiber filt er, a polyvinyl chloride filter, a polytetrafluoroethylene filter, an elect rostatic precipitator, and two light-scattering devices. Most gravimetric m ethods show discrepancies because mist droplets, which have a high surface area, evaporate from the filters during sampling. Inconsistencies occur wit h lightscattering devices because these instruments are sensitive to partic le size distributions, shapes, and refractive indices. Results from laborat ory and field experiments show that concentrations measured using these met hods vary by factors of two to five. Discrepancies were greatest when oil m ist concentrations were relatively low.