Abstract: On January 22, 1993, Employee #1 and several coworkers were pulling a geothermal drill pipe from its hole when they noticed that the pipe was plugged. Normally, mud is circulated through this system, but in this case, the one-way valves were later discovered to have failed. While the last few sections of the pipe were being removed, the surrounding air was checked for hydrogen sulfide using detector tubes. At this time, according to Employee #1, the hole started spitting out black sulfur water and hydrogen sulfide. When Employee #1 bent over to set the slips, he got a whiff of the hydrogen sulfide, felt light-headed, and was overcome. He was given oxygen and felt better. He was not hospitalized.