Abstract: On June 29, 1989, a mechanical failure in a processor at Dow Corning caused the compressor to divert to a scrubber. Due to insufficient water pressure in the scrubber, approximately 70 lb of hydrogen chloride was released over a 5 minute period. The chemical formed a cloud which was carried by the wind (which was blowing 10 mph from the east) to the Namex construction site approximately 800 yards away. (Namex is a part of Dow Corning). No alarm was sounded. The only warning sign was the cloud. Employees who saw the cloud alerted others and headed for the gates. Employees working on the structures or with their backs to the cloud had no warning until the odor from the cloud reached them. One employee was trapped on the cable tray throughout the entire 2 to 4 minutes of exposure. He was taken by ambulance to the hospital; 47 other exposed employees followed in cars shortly thereafter. Employees #1 through #48 were treated and released. Very few experienced any adverse health effects. With the exception of one employee, all were fully recovered by the next shift. That employee recovered in 2 days.