I wasn't able to find specific documentation on the height requirements for a space to be classified as a permit-required confined space in our current safety knowledge base, but here are industry-standard safety guidelines:

While specific height requirements aren't defined, a permit-required confined space is typically characterized by the following:

1. Size and Configuration: It must be large enough and configured so an employee can fully enter the space and perform work there. A space that is large enough for an employee to squeeze into, but not perform work, may not meet the confined space definition. 2. Limited Entry/Exit: The space must have limited means of entry and exit that could hinder escape, first aid, rescue, or emergency response. Ditches, wells, and trenches can be confined spaces if access or egress is limited, even if they have open sky above. 3. Not Designed for Continuous Occupancy: The space is not designed or intended for continuous human occupancy.