Improving estimation of real-time concentration for inhalable particles < 10 microm from a light scattering monitor.

This study evaluated the relationship between the real-time concentration measurements of inhalable particles whose diameters were less than 10 microm, from a light scattering monitor and a beta gauge monitor, at various instantaneous relative humidities. This work demonstrated that the mean inhalable particle concentrations as measured by the light scattering monitor were higher than those of the manual sampler, such that a factor of 0.74 was employed to adjust the light scattering monitor for inhalable particle concentration measurements. The mean inhalable particle concentrations determined by the beta gauge monitor at a low relative humidity setpoint correlated well with those obtained by the manual sampler. The real-time inhalable particle concentration of the adjusted light scattering monitor was further compared to those of the beta gauge monitor to investigate the effect of instantaneous relative humidity on the mass readings of the automatic monitors. The results demonstrated that the estimated concentration measurements by the adjusted light scattering monitor should be re-calibrated in real-time to improve the accuracy of the inhalable particle concentrations at various instantaneous relative humidities.

Measurements of respirable dust and nanoparticle concentrations in a titanium dioxide pigment production factory.

This study compared respirable dust and nanoparticle concentrations measured by different sampling devices at a titanium dioxide pigment factory. Respirable particle mass concentrations, nanoparticle concentrations, particle size distribution and particle metallic content were measured at different sampling locations. The sampling results of the Multi-orifice Uniform Deposit Impactor (MOUDI) showed that the particle size distribution at this titanium dioxide production factory fell in the range of 1-10 mu m. Generally, the higher levels of the respirable particle mass concentrations and nanoparticle number concentrations were near the packing site of the pigment titanium dioxide production factory. Metal analysis results revealed that the titanium dioxide concentrations in respirable dust and nanoparticles were within the limits specified by National Institute for Occupational Safety and Health (NIOSH). During sampling, particle metallic content analysis is essential for identifying the source of particles and for measuring respirable dust and nanoparticle concentrations.