RESUMO
Since 1995, Hery's trichloramine sampling procedure has been widely used to determine trichloramine exposure in indoor swimming pools. This method consists of pumping air at a 1 L/min flow rate for 2 h through a Teflon prefilter and two quartz fiber filters. Modified Hery methods have been reported using different sampling pump flow rates and types of prefilters. It is possible that the prefilter type or sample collection pump flow rate influenced the results of these studies. This study is designed to evaluate the effects of different cassette assemblies and sampling flow rates on the levels of measured trichloramine. Laboratory tests were performed using a trichloramine production setup designed for this study. Workplace measurements were carried out at four indoor swimming pools. Different prefiltering strategies were used: no prefilter, glass prefilter or Teflon prefilter in the sampling cassette, and an original separable prefilter cassette is presented in this study. Laboratory tests indicated that at trichloramine concentrations higher than 1 mg/m3, the percentage of trichloramine captured on the first filter could be less than 75%, which demonstrated possible loss of the material during sampling. An investigation of the prefilter effect on the sampling strategy using different cassette assemblies revealed that using a separable cassette assembly prevented overestimations of trichloramine levels. Furthermore, there were no significant differences between trichloramine concentrations measured at flow rates (from 0.5 to 2 L/min) in swimming pools.