Confined spaces are high risk workplaces that can easily result in multiple deaths. The challenge in managing confined space is the fact that the space might become high risk only when activities are conducted within the space. Without the activities contaminants or oxygen levels might not be at dangerous levels. For example see this case, which describes how a well becomes high risk because the workers placed a pump into the well. This resulted in accumulation of carbon monoxide and the death of two workers.
Training of all confined space workers are especially important, because the workplace can become dangerous simply because of mistakes made by the workers. These front-line workers must be able to identify how their activities create hazards.