What safety precautions are taken for working aloft on a ship?

Working aloft is controlled with a level of procedure that can seem heavy for what looks like a simple job, but a fall from height at sea, onto a steel deck, into machinery, or over the side, is unforgiving, and the risk does not shrink just because the task looks minor.

Before anyone goes up, the job is assessed for what has to be done, how high, what equipment is needed, and the weather and sea state, and a permit to work is raised confirming the precautions are in place, with the officer of the watch informed so the ship's operations account for someone working at height. The person going aloft wears a full-body safety harness clipped to a proper strong point or rigged lifeline, never to convenient but unchecked rigging, so a slip becomes a controlled arrest rather than a fall. A second person stands by at the base in constant contact, watching for trouble and ready to raise the alarm, and is not diverted onto other tasks while attending.

The means of access, a bosun's chair, staging, cradle or ladder, is inspected before use: ropes and slings checked for wear, shackles moused or pinned, blocks free-running, and the rig tested before anyone commits their weight to it. Tools and materials are secured with lanyards or carried in a closed bag, since a dropped item from height is a serious hazard to anyone below, and the deck area underneath is roped off for the duration.

Certain shipboard hazards get specific controls. Radar scanners and radio transmitters near the work are switched off, isolated and tagged so nobody energises them while a person is near the antenna or in the beam, since radar radiation and RF burns are real risks. The ship's whistle is isolated so it cannot sound near someone working on or near the funnel or mast, and funnel work accounts for hot surfaces and exhaust gas. Work over the side adds drowning risk, so a lifebuoy is kept at hand and, depending on the job, a rescue boat may stand by. Wherever possible the job waits for calm weather and a steady ship, because working aloft with the mast describing a wide arc in a seaway is a different and much harder problem than the same job alongside.