Abstract: Employees #1, #2, #3 and #4 were in an area where Hydrofluoric acid was being released to the flare line. Two control valves connected to a string of hoses being used to drain off the G-Fin to the flare were left open. When the drain line became charged, it disconnected at one of the hose connections, releasing a vapor cloud of hydrofluoric acid to the atmosphere. Three Employees working in the area of the alki unit were overcome by the vapor cloud. Two of the three employees sustained additional injuries as they were trying to get out of the area. Two employees were taken to a local hospital. One was treated and released and one was admitted for observation. Two other employees were flown to another hospital and treated for minor acid burns and other injuries.