The image below is just one I found on the internet, but it is a good representation of the ones I have seen and worked with.
Today, during an audit, I was asked by the EHS pro, if I thought there large CNC machines were Confined Spaces/Permit-Required Confined Spaces. At first, I said I did not think so, but was we stood there and began assessing the space, we came to the conclusion that it meets all three (3) of the characteristics of a CS:
