"Many workplaces contain spaces that are considered to be 'confined' because their configurations hinder the activities of employees who must enter into, work in or exit from them. In many instances, employees who work in confined spaces also face increased risk of exposure to serious physical injury from hazards such as entrapment, engulfment and hazardous atmospheric conditions. Confinement itself may pose entrapment hazards and work in confined spaces may keep employees closer to hazards such as machinery components than they would be otherwise. For example, confinement, limited access and restricted airflow can result in hazardous conditions that would not normally arise in an open workplace. The terms 'permit-required confined space' and 'permit space' refer to spaces that meet OSHA's [Occupational Safety and Health Administration] definition of a 'confined space' and contain health or safety hazards."
OSHA 3138-01R 2004
Lessons Learned Information Sharing (LLIS)