Initial Free Available Chlorine (FAC) concentration required?

• A. 100 ppm
• B. 200 ppm
• C. 300 ppm
• D. 400 ppm

Answer: (B)

Free available chlorine strength in a sanitizer must be high enough at the start to stay effective after it’s diluted by soil and organic matter and during the required contact time. When using chlorine for sanitizing equipment or surfaces, an initial FAC around 200 ppm is commonly used so that, even after some chlorine is consumed by organic load, the solution still provides an adequate sanitizing residual (typically in the range needed for disinfection).

Starting with too low a concentration (like 100 ppm) may not maintain the necessary residual once soil and use reduce it, while starting at levels as high as 300–400 ppm is often unnecessary and can risk corrosion or safety concerns. Thus, 200 ppm is the best balance to ensure effective sanitation under typical conditions.