Quantification of Bypass Leakage in Two Different Filter Cassettes During Welding Fume Sampling

Abstract

In South Africa, filter cassettes are used in personal samplers designed for occupational hygiene measurements. One problem envisaged during the sampling of welding fumes was a possible dust loss due to bypass leakage. This could lead to an underestimation of a worker's total aerosol exposure and therefore constitutes a health risk. Bypass leakage was quantified by using two different dust collecting cassettes in laboratory environments. Additionally, a field study for the quantification of bypass leakage in terms of dust loss was carried out in a welding shop. A significant difference existed (P<0.05) between the two filter cassettes at the 95% confidence level. The results showed that representative dust sampling cannot be done without measuring the pressure drop across filters assembled in filter cassettes. It also showed that certain cassettes are more effective in reducing bypass leakage during sampling. Appropriate procedures for testing internal leakage were established to minimize the risk of unde...