Design your scrubbing systems properly

Scrubbing systems are your last line of defence. Ensure that adequate redundancy is provided to ensure that the system will work properly when needed. In an incident the CSB investigated, excess chlorine vented to a scrubber where it completely depleted the active scrubbing material (caustic soda), over-chlorinating the scrubber. The resulting decomposition reaction vented chlorine vapors to the atmosphere. Hazardous emissions continued for about six hours and led to the medical evaluation of five residents and 11 police officers, and the evacuation of 1.5 square miles. Read the CSB recommendations in this link.