When added to a swimming pool, bromine kills bacteria or harmful contaminants that reside in the water. Unlike chlorine, another popular disinfectant for pools, bromine stays active in the water after additional chemicals have been introduced to purge the disinfectant. This allows the chemical to work over multiple cleaning cycles.
Like chlorine, bromine is highly reactive in water. After the chemical initially sanitizes the pool, the molecules produced in the cleaning process, called bromamines, continue to attack and oxidize any bacteria left or reintroduced in the water. By comparison, leftover chlorine molecules are largely ineffective in this secondary process.
Bromine is susceptible to ultraviolet degradation and, thus, is often used in smaller pools or indoor facilities to ensure the chemical's effectiveness. Bromine also tolerates warm temperatures, which is why it is most often used in spas or hot tubs.
Bromine is less likely than chlorine to become airborne once introduced to water. The chemical also dissolves slower than chlorine.
There are negative health effects associated with bromine, particularly when the undiluted chemical is exposed to skin. The results can range from skin irritation to significant chemical burns. Depending on the level of bromine in the water and an individual's sensitivity to it, bromine can cause minor skin and eye irritations and rashes.