An empirical model for estimating the collection efficiency of dust-mist respirators.
Brosseau LM; Evans JS; Ellenbecker MJ
Ann Occup Hyg 1993 Apr; 37(2):135-150
An empirical model for estimating the collection efficiency of dust and mist respirators was derived. The model was developed because the commonly used single fiber efficiency model could not reliably predict the penetration characteristics of aerosols in which electrostatic forces were important. The model was derived using data obtained in a study of dust and mist respirator penetration by monodisperse spherical latex particles. The overall fractional penetration of the aerosol was expressed as a differential function of the product of a size specific penetration function and a probability distribution function. The penetration function was approximated by the two parameter Weibull function. The probability distribution function could be formulated as either a count or mass median distribution function. The equation was integrated by numerical methods. The model was applied to predicting the collection efficiency of three commercial dust and mist respirators for silica (14808607) and asbestos (1332214) aerosols. Agreement between the predicted and experimental values for silica was excellent for two respirators. The model overestimated penetration of the third respirator by a factor of about 10. Agreement between the experimental and predicted values in the case of asbestos was poor. The model overestimated penetration of all three respirators by factors of 10 to 100. The authors conclude that the model accurately predicts the penetration characteristics of isometric aerosols such as silica. It fails when attempting to predict the penetration characteristics of fibrous dusts such as asbestos. This reflects differences in the physical characteristics between asbestos fibers and the spherical latex particles on which the model is based.
NIOSH-Publication; NIOSH-Grant; Respirators; Training; Mathematical-models; Aerosol-particles; Industrial-hygiene; Asbestos-fibers; Silica-dusts
Physiology Department, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115
Annals of Occupational Hygiene
Harvard University, Boston, Massachusetts