Wood Dust Particle and Mass Concentrations and Filtration Efficiency in Sanding of Wood Materials

Abstract

The importance of fine particles has become apparent as the knowledge of their effects on health has increased. Fine particle concentrations have been published for outside air, plasma arc cutting, welding, and grinding, but little data exists for the woodworking industry. Sanding was evaluated as the producer of the woodworking industry's finest particles, and was selected as the target study. The number of dust particles in different particle size classes and the mass concentrations were measured in the following environments: workplace air during sanding in plywood production and in the inlet and return air; in the dust emission chamber; and in filter testing. The numbers of fine particles were low, less than 10⁴ particles/cm³ (10⁷ particles/L). They were much lower than typical number concentrations near 10⁶ particles/cm³ measured in plasma arc cutting, grinding, and welding. Ultrafine particles in the size class less than 100 nm were found during sanding of MDF (medium density fiberboard) sheets. When the cleaned air is returned to the working areas, the dust content in extraction systems must be monitored continuously. One way to monitor the dust content in the return air is to use an after-filter and measure pressure drop across the filter to indicate leaks in the air-cleaning system. The best after-filtration materials provided a clear increase in pressure drop across the filter in the loading of the filter. The best after-filtration materials proved to be quite effective also for fine particles. The best mass removal efficiencies for fine particles around 0.3 μm were over 80% for some filter materials loaded with sanding wood dust.

Keywords:

• dust emission
• filtration efficiency
• nanoparticles
• particle size distribution
• wood dust

ACKNOWLEDGMENTS

The authors thank Kaukas Plywood Mill in UPM-Kymmene Corporation for participation in the project.

This study was supported by TEKES, the Finnish Funding Agency for Technology and Innovation, in the program of FINE Particles—Technology, Environment and Health 2002–2005.