Confined space entry is sometimes treated as a fall protection problem with a vertical twist. The requirement is different in one important way: the harness may be used to lift or lower a person, either to place them into the space or to recover them from it. That changes what the harness must have.
Retrieval points, not only a fall arrest point
A harness intended for entry and rescue carries attachment points that let the person be raised or lowered in a controlled way. A dorsal (rear) attachment is used for fall arrest and for vertical lifting; shoulder or front points are used where the rescue plan calls for a particular orientation. A harness with a single point, chosen for fall arrest alone, may not support the retrieval the rescue plan describes. The entry point and the rescue method are decided first, then the harness is matched to them.
Compatibility with the entry point arrangement
The harness has to work with the equipment at the opening: a tripod or davit with a winch or a self-retracting lifeline, and a retrieval line. The connector on the harness has to mate with the line, and the harness must not snag on the opening or on the internal fittings of the space. Where the worker also wears breathing apparatus or carries instruments, the harness should not interfere with either.
Fit, because the space is unforgiving
Inside a vessel or a tunnel the worker may be crouched, reaching or turning in a way that a harness on a flat rooftop does not have to accommodate. A harness that rides up, twists or catches on fittings becomes a hazard of its own. Correct size and adjustment, checked before entry, matter more here than in open air, and clothing or PPE worn underneath changes the fit.
What monitoring adds at the opening
Fall detection and wear detection on a harness tell the attendant and the supervisor whether the harness is on and whether it is attached, at the moment it matters. Combined with the entry monitoring station, this links the harness to the people count and the permit, so that a harness removed inside the space is visible as an event rather than discovered afterwards.
The harness is one part of a system. Entry control, atmospheric testing, the attendant, communication and the rescue plan all remain requirements. The harness is chosen to serve the rescue plan those arrangements depend on.