Understanding Decompression Protocols for North Sea Saturation Diving
The Byford Dolphin was a North Sea oil platform that operated from 1980 until it was decommissioned in 2015. The name "Byford Dolphin Map" most commonly refers to the decompression chamber protocols and saturation diving tables associated with the platform's diving operations, or more broadly, to charts used by saturation dive teams operating in the North Sea region where that platform was based. If you're looking for actual decompression schedules, you won't find a single "Byford Dolphin Map" floating around as a downloadable file. These tables are proprietary and regulated. But I can walk you through how they work, where to get legitimate versions, and what actually matters when you're working with them. Decompression tables for North Sea saturation operations are maintained by certified dive contractors and published through organizations like the British Sub-Aqua Club (BSAC), the International Marine Contractors Association (IMCA), and commercial diving safety bodies. The IMCA documents are the closest thing to a standard reference. IMCA D 022 and IMCA D 014 cover saturation decompression procedures and compression systems respectively. You can access these through the IMCA website if you're a member or affiliated company. Some dive shop suppliers like Dräger and Seatech also publish operational summaries that include decompression planning references. For the actual decompression schedules, you need either your company's approved dive plan or a licensed hyperbaric physician. These aren't documents you casually download and use. Using someone else's decompression table without proper approval is a liability issue and, more importantly, a safety issue. I've seen divers try to reuse older tables from decommissioned platforms. It doesn't work the way you'd hope. Environmental conditions, saturation gas mixes, and chamber hardware all affect the actual schedule.
How saturation decompression tables actually work
Saturation diving means the diver lives at pressure for days or weeks. Their tissues saturate with inert gas — usually helium mixed with hydrogen or neon depending on depth. When it's time to come back up, the decompression isn't a simple ascent. It's a multi-day process in a hyperbaric chamber. The "map" or table shows gas percentages, pressure stages, rest periods, and breathing gas switches across the decompression timeline. The key insight most beginners miss is that saturation decompression tables are depth-specific and gas-mix-specific. A table built for 200 meters on heliox won't apply at 150 meters, and switching from helium-hydrogen to helium-neon changes the off-gassing curve significantly. I worked a job where the dive superintendent tried to apply a standard North Sea table to a deeper wellhead operation. The decompression time estimate was roughly half of what it actually needed to be. We caught it before committing the team to the chamber, but it would have been a serious incident. Always verify your depth and gas mix against the table's parameters before starting. Another thing that isn't obvious: these tables assume your saturation dive platform is functioning correctly. Chamber temperature, scrubber efficiency, and gas blending accuracy all feed into whether the schedule holds. I once spent an extra six hours in decompression because the platform's temperature control was drifting during the final stage. The table didn't account for that variance, and the diving supervisor had to make a call. That's when having a hyperbaric physician on standby — or at least on call — matters. The schedule is a guideline, not a guarantee.
Common pitfalls when using decompression schedules
The biggest mistake I see is treating the table as a rigid script. It's a starting point, not a law. Divers who deviate from the schedule due to health issues, equipment problems, or unexpected depth changes need real-time adjustment, not blind adherence. The second mistake is ignoring the rest periods. The tables build in deliberate rest stages where inert gas off-gassing slows naturally. Skipping or compressing those stages to save time is how decompression illness happens. I've never seen a shortened decompression schedule result in a better outcome, only in more medical consultations afterward. A third issue is gas mixing accuracy. If your helium concentration drifts even a couple of percent during a switch, the tissue loading model shifts. The table becomes wrong. Check your gas analyzers before every stage transition. I do this religiously now. Early in my career, I skipped the check on a routine switch and didn't notice for two hours. The decompression was technically still within the approved envelope, but barely. We ran a conservative extension anyway. It added eight hours to the shift but it was the right call.
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Limitations and when tables fail
Decompression tables are models, not reality. They're based on bubble dynamics and tissue compartment theory — mostly the Haldane model refined over decades. No table accounts for individual physiology well. Two divers at the same depth, on the same gas, following the same schedule, can have different outcomes. Age, fitness, hydration, and prior dive history all matter. The tables also don't handle emergency decompressions well. If you need to surface fast due to an incident, the schedule goes out the window and you rely on emergency protocols, not the standard table. For very deep operations above 300 meters, standard North Sea tables may not apply at all. You enter what's called the "extreme saturation" zone where different gas mixtures and decompression models are needed. I haven't worked that deep, but the contractors who do report that they use customized tables developed with their medical team rather than any published standard. If your operation goes beyond typical North Sea depths, don't rely on generic references. Get a proper medical dive plan.
Practical takeaways
If you're planning saturation diving work in the North Sea region, start with IMCA guidance and your company's approved dive plan. Don't improvise with outdated tables. Verify depth and gas mix compatibility before committing to any schedule. Build in buffer time for equipment drift and environmental variation. Keep a hyperbaric physician involved throughout the decompression process, not just at the start. And treat the table as a living document that may need adjustment based on what's actually happening in the chamber, not just what's written on paper.
