Comparison of Gravimetric and Photometric Methods in Determining Low Mass Concentrations of Airborne Wood Dust

Abstract

The sensitivity of an optical device was evaluated when determining the mass concentration of inhalable wood dust under conditions where workers' exposure was below 0.25 mg/m³. Samples were collected during the processing of oak wood using a belt sander (BS) and thermally modified (TM) ash wood using a four-sided planer (4SP). The Split2 (SKC) optical device, operated in active mode, consists of an optical sensor and an inlet component with an Institute of Occupational Medicine (IOM) filter holder for inhalable dust. Gravimetric determination of respirable and inhalable dust mass concentrations was performed using a Higgins-Dewell respirable dust cyclone and an IOM inhalable dust sampler. Measured exposure levels for the inhalable fraction near the BS and 4SP machines ranged from 0.02 to 0.219 mg/m³ (N = 18). The Split2 optical device significantly overestimated the inhalable dust concentration during the belt sanding operation (p = 0.02). This overestimation may be related to the high average proportion of the respirable fraction (70.3%). However, no statistically significant overestimation was found for the four-sided planer operation (p = 0.13). Based on the ratio of gravimetric to photometric mass concentrations, two specific photometric correction factors are recommended for the Split2 optical device under these specific working conditions: 0.24 for the belt sander and 0.48 for the four-sided planer.