Pipeline work has an unpleasant property: gas conditions change as the crew advances. The pre-entry test passes; twenty metres in, sludge disturbed at the pipe bottom releases hydrogen sulfide. A single pre-entry reading is a starting point, not a clearance.
Why continuous monitoring is the baseline
The gas detection deployment ball advances with the work face and readings refresh continuously — oxygen, H2S, CO and combustible gas. GB 46768-2025, the safety technical code for confined space operations effective 1 May 2026, requires recording intervals of no more than 15 minutes during work. A pace that manual log-keeping cannot hold is exactly why continuous monitoring with automatic records has become the practical baseline on municipal pipeline projects.
Three retreat rules for pipeline geometry
- Retreat along the entry direction to the nearest opening. The far end of a long pipeline may not be open at all — do not look for an exit deeper in.
- Do not cross low-lying or waterlogged sections. H2S is heavier than air and concentrates near the pipe bottom; the low section is where the gas is.
- Tools stay inside; people come out first. Once outside, count heads and report to the attendant. Re-entering after an interruption requires re-testing — stated in the storage tank cleaning and confined space codes, and pipelines are no exception.
Hand the judgment to the person at the opening
Retreat should not be decided by the workers inside the pipe. Shouting cannot be heard and the attendant cannot see them — so alarms must reach his eyes. The Yunku LSM3000 series confined space monitoring box separates indoor and outdoor units: the indoor unit follows the work face, the outdoor unit stands at the entrance, and gas curves, headcount and site video concentrate on its screen, with alarms pushed to phones simultaneously.
Offline, the device's local sounder and beacon still work — the evacuation call does not depend on the platform being online.
The check worth doing on any pipeline project. Take the farthest work position and trace the alarm path: who receives the exceedance first, how many seconds until the crew inside hears it, and what stands in between. If the answer is "the attendant sees the screen, then shouts", the last metre of the safety chain is the weakest one.