Burnout 73 is a super-chlorinator for swimming pools. It has the highest percentage of calcium hypochlorite of all the BioGuard shocks. Product Information: Calcium Hypochlorite 73% Other Ingredients 27% One bag treats 16,500 gallons of swimming pool water One of the strongest shocks on the market Add this product at night or when the pool is not in use Shock at least once a week during periods of heavy use or when water temperature is above 80 degrees fahrenheit Keep your pump and filter running after application Do not enter the swimming pool until chlorine residual is below 4.0 or less as measured by a proper test kit