Abstract: A CONSULTANT FOR A GEOTHERMAL ELECTRIC UTILITY WAS STANDING AT A WELLHEAD NEAR A 2-INCH BYPASS. THE GAS CAP CAME TO THE SURFACE AND FLOODED THE AREA WITH A SUBSTANTIAL AMOUNT OF HYDROGEN SULFIDE. THE CONSULTANT RAN AND COLLAPSED ABOUT 150 FEET NORTHWEST OF THE WELLHEAD. HE DID NOT LOSE CONSCIOUSNESS, HOWEVER, AND QUICKLY REGAINED HIS BALANCE. A CHEMICAL TECHNICIAN, WHO WAS PERFORMING DAILY AIR MONITORING, WAS ALSO OVERCOME BY THE HYDROGEN SULFIDE RELEASE. HE DONNED A SELF-CONTAINED BREATHING APPARATUS NEAR THE GROUND, BUT COLLAPSED BEFORE HE COULD TURN THE AIR ON. HE WAS REVIVED WITH OXYGEN. BOTH EMPLOYEES RECOVERED FROM THEIR INJURIES.