Abstract: A contractor was hired to come on site and "acidize" a clogged water disposal well. The well was located in a 7 ft deep concrete vault. To unclog the well, the contractor put a hydrochloric acid mixture in the well's tubing. He warned the company that this process had the potential to form hydrogen sulfide in the well. After the contractor left the site, Employee #1 entered the well to replace a broken valve. When he broke the seal on the valve, hydrogen sulfide was released into the confined space and Employee #1 was asphyxiated. Coworkers found him later slouched over in the well vault. The autopsy concluded that he died of hydrogen sulfide intoxication. The well was not a permit-required confined space.