Recreational facilities’ indoor swimming pools provide a venue for exercise, competition and fun for all ages as patrons splash, swim, dive and float around in the crystal clear water. To keep the water fit to swim in requires a disinfectant maintenance program commonly using Chlorine, or Chlorine and Ozone. Chlorine is a powerful, corrosive disinfectant and in both gas and liquid forms it is toxic and hazardous to living beings at concentrations as low as 1 ppm. Ozone is created by exposing oxygen to a high voltage or ultraviolet radiation. It is more powerful than Chlorine and when used in conjunction with Chlorine it helps provide an odourless, clear water environment. The potential for gas leaks from the equipment used to produce the Chlorine and Ozone are found in the Chlorine feed room and the Ozone generator room. This article describes the considerations for an appropriate gas detection system to continuously monitor and alarm if the gas levels reach concentrations that risk human health and safety.