The Indoor Environment During Swimming Competitions and Its Impact on Construction Materials: Airborne Trichloramine as a Degradation Factor

Swimming is one of the most popular forms of recreational sport worldwide, recommended for people of all ages as a healthy activity. While numerous studies have focused on the impact of indoor air quality on the health of pool users, relatively few have addressed how specific airborne parameters in indoor swimming facilities affect the durability of construction materials. This article analyzes the current state of knowledge on the influence of the pool indoor environment on structural reliability, with trichloramine (NCl3) emphasized as a degradation factor. Indoor pool environments are classified as chemically aggressive, due to elevated air temperature (~30 °C), high humidity (often exceeding 60%), and the presence of volatile chlorine compounds released from disinfected water. Our case study demonstrates that during swimming competitions, the average concentration of airborne NCl3 reached a value of 900 µg/m3, with peaks up to 1200 µg/m3, i.e., about ten times higher than on typical usage days. The median trichloramine concertation during the competition was 1071 µg/m3. Such exposure conditions accelerate corrosion processes in stainless steels and other building materials, reducing service life and requiring targeted monitoring and preventive maintenance. Based on the findings, recommendations are provided regarding material selection, highlighting the importance of surface texture, ventilation strategies, and protective measures tailored to periods of intensive facility use.