Trichloramine (NCl3) is a disinfection by-product commonly found in the water and air in indoor swimming pools. The gas is associated with chronic diseases such as asthma and often causes eye and skin irritation. Due to its higher density than air, NCl3 tends to accumulate close to the water surface and above the deck. Mixing ventilation is the main ventilation strategy used in aquatic centers to maintain the NCl3 concentrations at an acceptable level. However, swimming pool halls are known to be significantly energy-intensive, mostly because of water evaporation from the basin. Consequently, building codes recommend maintaining a low airspeed above the pool and deck to minimize evaporation and to ensure swimmers’ thermal comfort. If trichloramine levels are suspected to be too high, pool managers will favor increasing the number of air changes per hour (ACH) while limiting the outdoor air (OA) intake. However, mechanical filtration systems are not designed to remove NCl3 from the airflow. Since its concentration cannot be measured directly, ventilation system parameters are often based on minimum recommendations set out in building codes and may vary in operation according to the CO2 levels in the extracted air, irrespective of the NCl3 level and its accumulation behavior. It remains unknown how the OA intake ratio affects NCl3 levels in breathing zones. This study carries out a numerical investigation of the impacts of the OA and the ACH on NCl3 concentrations in a swimming pool hall in Montreal (Canada). Results show that the minimum recommendations (OA intake and ACH) by ASHRAE are not sufficient to eliminate NCl3 accumulation and stratification in the lower breathing zones. Moreover, air recirculation mostly affects the breathing zones of standing occupants on decks and of lifeguards but has a smaller impact on the breathing zones of swimmers or people sitting on the deck. Eliminating air recirculation does not guarantee better air quality in terms of NCl3 in these breathing zones. The findings for the complex under study may be used to guide similar research in other aquatic centers and for the continuous development of building codes and air quality standards.
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 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. Might the prefilter type or sample collection pump flow rate have influenced these studies' results. 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 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.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.