Gas chlorination typically uses gaseous chlorine that is dosed into potable, process, reclaim, and waste waters prior to distribution.  Often, these systems use vacuum operated feeders offering maximum safety, and allowing flexible designs for different control strategies.  It is typically one of the least expensive methods of chlorination for disinfection or biocide control, but comes with inherent risks that must be mitigated through management, training, and proper application to avoid harmful byproducts.