The hazard
Confined spaces can look harmless from the outside. The air inside can be short on oxygen or hold toxic or flammable gas you may not see or smell, and loose material like sand or grain can bury a worker. When someone goes down, the natural reaction is to rush in and help, and that can turn one victim into two.
The action
Permit spaces have serious hazards, and exposed workers must be told where they are and what the danger is, by danger signs or another equally effective way. If you are not authorized to enter, you stay out, even to grab a tool or take a quick look. Keep covers and barriers in place so nobody walks in by mistake. (29 CFR 1926.1203(b)(1))
ASK THE CREW
Who on this crew is trained as an entrant, an attendant or an entry supervisor?
From the talk: Confined spaces. Read it in full, free, with the questions and the sign-in sheet.