Abstract
Accepted practice by most professional industrial hygienists in government and industry is to use “closed-face” filter cassette techniques as standard sampling procedures for the majority of aerosols. A two-phase, field study was conducted to determine whether a gravimetric bias exists between “open” and “closed-face” sampling methods. Phase I involved an in-depth analysis of the potential gravimetric viability as it applies to an industrial paint spray mist, and Phase II was a series of pilot studies, of small sample base, to determine if this phenomena exists over a range of aerosol types. Dusts of wood, grain, cellulose, Portland cement and perlite, welding fumes, and chromic acid mist were sampled in Phase II. Paired breathing zone samples, “open” and “closed-face”, 37 mm, 3-piece filter cassettes were utilized in both phases of the study. In both phases of the study, “open-face” concentrations were consistently higher than “closed-face” concentrations, with the exception of cellulose dust. Based on the concentration for both sampling techniques, the data suggests that “closed-face” sampling techniques (4.0 mm inlet diameter) might be size selective against large particles. This could lead to an underestimation of a worker's total aerosol exposure.