Particle Size Distribution of Submicron Cotton Dust Using Transmission Electron Microscopy

Abstract

The particle size distribution (PSD) of dust generated while processing cotton on a card and collected on grid substrates by free settling was examined by transmission electron microscopy (TEM). The dust was collected in a model card room imme diately after stopping the card, as well as when the card was in operation. The air circulation conditions in the room were varied by shutting off, either together or individually, the lint capture system, the air conditioner, and the electrostatic pre cipitator along with the card. Grids were also charged to a potential of 5000 volts, both positively and negatively, to discern the effects of charging on PSD and col lection efficiency. The average particle size of cotton dust collected by this technique was much smaller than that previously measured on dust collected on filters and observed with light or scanning electron microscopy (SEM). The higher resolution of TEM revealed a new lower diameter distribution of cotton dust with a mean diameter of approximately 0.09 μm. Previous SEM studies suggested, but could not verify, the existence of this additional distribution of lower mean diameter.