Abstract: At 10 p.m. on 3/19/18, an employee and coworker were performing preventative maintenance on a chlorine gas system used in a water filtration process. The employee and coworker were removing, and reinstalling, a flange with a black Teflon rubber gasket. They were working in a 48-foot long, 24-foot wide, and 6-foot tall crawl space under a chlorine cylinder storage building. The schedule 80 polyvinyl chloride (PVC) chlorine pipes that were connected to the flange were under vacuum and purged before the work began in an attempt to remove residual chlorine gas. The employees were required to wear a Scott Industrial Self-Contained Breathing Apparatus (SCBA), 4,500 PSI, with a Scott Full Face piece as protection against any residual chlorine gas. Near the end of the work, the employee adjusted their tight-fitting, elastomeric facepiece and inhaled residual chlorine gas. The employee became agitated and while attempting to exit the crawl space further dislodged the tight-fitting elastomeric facepiece. The employee was hospitalized. The employee was reported to have a beard.