A confined space accident or fatality often results from a complex set of circumstances, which commonly include either oxygen deficiency, a hazardous atmosphere involving an airborne chemical contaminant, or both. In addition, mechanical, electrical, pneumatic or other hazards may have contributed to the accident. Often a number of failures have occurred, which may or may not be causally related to the incident and must be sorted through. These may include failure to identify or properly classify the space as a permit-required confined space, an improperly designed entry protocol, failures in implementing designated entry procedures, failure to properly respond to changing conditions, lack of adequate training for members of the entry team, or an inadequately considered emergency response plan.