Confined space entry is one of the most hazardous tasks a worker can encounter. What makes it so difficult is that workers often fail to recognize potential hazards.
Fatalities associated with confined space entry are most commonly the result of atmospheric circumstances, which are often difficult to immediately detect. Hydrogen sulfide and carbon monoxide are two of the most common poisonous gases found in such instances. In a NIOSH study of confined space entry fatalities from 1983-1993, 45 percent of deaths were caused by asphyxiation, or suffocation, due to an oxygen-deficient environment.