This depends upon your local health code. In many areas, the level is 50-100ppm available chlorine. It is best to check with your local health inspector for the level required in your area. Federal regulations (21 CFR Part 178) permit the use of hypochlorite solutions on food processing equipment and contact areas (tables) but state that solutions used for sanitizing equipment not exceed 200ppm available chlorine. If higher concentrations are used, a final rinse in potable water is required.