Pool safety is not something to be taken lightly. Water recreation provides a lot of fun, exercise, and social interaction, but it also holds hazards. Pool chemicals, including chlorine and acid, are unstable substances that can be lethal when not handled properly. Chlorine is necessary to keep water clean and sanitary. There needs to be at least 1 part per million (ppm) of chlorine in pools and 3 ppm in hot tubs to maintain a safe environment. Acid serves to balance pH levels.