Cotton dust sampling, III-estimation of statistical errors with vertical elutriators

Cotton dust levels measured by vertical elutriators have been studied in terms of the variance components associated with statistical errors due to sampling equipment, location, time and repeated sampling. A thumb-rule is proposed for estimating sampling errors of three-hour vertical elutriator samples as a function of average dust level. Relative efficiency of three-hour samples is shown to be superior to that of six-hour samples at moderate dust levels (0.4-0.6 mg/m3) but inferior at low dust levels (0.1-0.2 mg/m3. Errors due to location and equipment are found insignificant from this particular study.