A confined space is any space that is large enough for an employee to enter, that has a restricted means of entry or exit, and that is not designed for continuous employee occupancy.

All of these criteria must be met for a space to be classified as confined. Examples of confined spaces include tanks, pits, certain tunnels, utility vaults, and boilers. The physical and atmospheric hazards often associated with confined spaces can cause serious injury or death to workers. The major factors that lead to injuries in confined spaces include failure to recognize and control these hazards, and inadequate or incorrect emergency response.

The Occupational Safety and Health Administration (OSHA) requirements apply to most activities that require entry into a confined space. Examples of specific activities include, but are not limited to, the following.

• Maintenance and cleaning of boilers
• Cutting or welding in confined spaces
• Telecommunications and electrical utility work performed in manholes and unvented vaults
• Work in excavations or trenches that could develop hazardous atmospheres
• Work in sewers, manholes, pits, traps and the like