Abstract
Short-term sampling of cotton dust has been carried out on instruments which utilize either a quartz microbalance (2 minute sampling time) or the attenuation of beta radiation (12 minute sampling time) to determine the mass of dust sampled. These measurements were compared with gravimetric measurements made with Vertical Elutriator Cotton Dust Samplers (ELU) and cyclone samplers designed to collect dust of <15 µm and <10 µm diameter respectively. Although correlations of most groups of data with ELU measurements for concentrations up to 1 mg/m3 have been excellent (correlation coefficients of from 0.92 to 0.94), the measurements of concentrations are not equal and must be related by a calibration curve. The mass measured by the ELU samplers is approximately 65% greater than that detected by the two instruments when they are fitted with preseparators having size cutoffs of >15 µm diameter. The mass detected by the two short-term samplers is about equal to that measured on the cyclone samplers (which collect particles of <10 µm diameter). Particle size distribution of airborne cotton dust has been measured directly by a light scattering instrument fitted with a 15 µm diameter cutoff preseparator. Calculation of the mass concentration from one of the measured distributions, assuming an average particle density of 1.5 g/cm3, corresponds quite closely to that measured simultaneously with the instrumental mass monitors (0.36 mg/m3 by light scattering vs. 0.40 and 0.43 mg/m3 measured with the short-term samplers).