Comparison of sampling collection strategies for assessing airborne trichloramine levels in indoor swimming pools

Abstract

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 hours through a Teflon prefilter and two quartz fibre filters. Modified Hery methods have been reported using different sampling pump flow rates and types of prefilters. This study aims 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 set-up designed for this study. Workplace measurements were carried out in 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. In this new assembly method, the prefilter is placed in a cassette alone and connected with a Tygon tube to the main cassette that has two impregnated fibre filters. Laboratory tests indicated that in the situation of trichloramine concentrations higher than 1 mg/m³, the trichloramine percentage captured on the first filter could pass the value of 75%, which demonstrates the possible loss of material during the sampling. The investigation of the prefilter effect on sampling strategy using different cassette assemblies revealed that using a separable cassette assembly could prevent overestimating the trichloramine levels. Furthermore, there were no significant differences between measured TCA concentrations at different flow rates (from 0.5 L/min to 2 L/min) in swimming pools.