Decompression Obligations on Commercial Jobs
By Dutch Hollander, Offshore diving superintendent. Reviewed by Dana Whitcombe, technical reviewer.
Commercial Diving Contractors Alabama | Commercial Diving Contractors Alaska Off Grand Isle, 2014. We had a diver on a 165-foot air dive, working a spool piece in a crosscurrent. He cleared the bottom, and the current pinned him on the downline. I still see him kicking at 30 feet, trying to make his stop. We got him up with a scratched arm and no decompression symptoms, but I sweated that ride for the rest of the shift. That's when it hit me again: decompression obligations don't start at the table. They start with the job plan. For a commercial diving superintendent, decompression obligations are a moving target. They're the legal and contractual duties to run every dive so that the pressure changes don't cripple or kill the guy in the water. That means using the right tables, the right gas, the right chamber availability, and the right records. It also means standing up to the client when they want you to push a bounce dive past the no-decompression limit because they're behind on a pipeline inspection. I've walked away from one of those in my career. No regrets.
Know Your Standard of Care
Your first obligation sits in the contract and the regulator. On commercial jobs in the Gulf, that's OSHA 29 CFR 1910 Subpart T, the ADCI consensus standards, and any client-specific addenda. These documents overlap, but they don't always match. Your job is to work under the most conservative applicable standard, call it the strictest rule that keeps everyone alive. That might mean following a client's custom table if it's equal to or better than the USN table, or it might mean telling the client their table is not going to fly. I've had clients argue for a modified decompression schedule because they wanted to save an hour of chamber time. I've said no. You need to know what your license and your employer's insurance require before you take a single diver in the water. The second part of that standard is your own competency. You can't satisfy an obligation you don't understand. That means sitting down with the tables or the software every time, not just eyeballing a dive plan from a previous job. The old US Navy Air Decompression Table is the workhorse for bounce air diving. For mixed gas and saturation, you're looking at Bühlmann ZHL-16 with gradient factors. Use ProPlanner or Abyss to check your work, but don't let the computer be the only brain in the chain. This is the core of commercial diving decompression: the obligation doesn't end when the diver leaves the water.
Plan the Gas and the Stop Schedule
Once you've set the standard, you plan the dive. For offshore IRM in the Gulf, most air dives stay inside the no-decompression limits, give or take a few jobs where you're in and out quickly. But your obligation is to treat every dive as if it could cross that line. That means planning the gas for a worst-case ascent: enough bottom gas to get you to the first stop, enough travel gas to move you up, and enough 100% oxygen on the helmet or at the line for the stops. On a 165-foot dive, I always have a spare bailout bottle with a higher oxygen percentage in the basket, even if I don't plan to use it. It's cheap insurance. The stop schedule itself is not a suggestion. You write it on a waterproof sheet, you post it in the control box, and you initial it before the diver hits the water. You also write a contingency schedule for one stop deeper and one stop longer. If the diver has a slow thumb or a stuck tool, you extend the schedule, not ignore it. And if you do modify it, you record that decision and tell the client in the end-of-day report. That's your obligation.
Run the Dive, Not the Schedule
The decompression obligation is not fulfilled by pinning a table to the wall. It's fulfilled by watching a depth gauge and a stopwatch in real time. Too many supervisors treat the table like a restaurant menu: they order what they want and then argue with the bill. On my watch, the table is the law. If a diver has to stay at 70 feet for ten extra minutes to fix a flange, then his bottom time is ten minutes more, and his decompression obligation grows accordingly. I've seen guys try to ignore that extra time because, 'It was only ten minutes.' That's how you end up with a hit. I tell my divers: if you see the supervisor pulling time off your stops, you call it out. That's not insubordination; that's a safety obligation. We also use a magnetic whiteboard that shows every dive's planned and actual stops. It's a plain piece of equipment, but it keeps us honest. It's also a damn sight better than the chalkboard we had on a North Sea job in the late '90s; the spray would wash the times off halfway through a dive, and we'd be arguing about numbers while the diver was hanging there. Good times. There are newer electronic systems that track this automatically, but they're only as good as the data you feed them. The supervisor has to be the one who says, 'The computer says we're fine, but the diver is cold and breathing hard, so we're going to add a two-minute stop at 30 feet.' That call is part of the obligation.
When It Goes Wrong, You Own It
Decompression sickness can happen on a perfect dive. Your obligation in that moment is to recognize it, treat it with 100% oxygen, and get the diver to a chamber. You should have the chamber phone number on a card in the control box, and you should know if the nearest chamber is on the rig, a vessel, or at the Port of Fourchon. Depends on the plant. In the Gulf, we often call DAN's emergency hotline, and they coordinate the medevac. That call happens on your watch. The paperwork is just as important. Every logbook entry, every stop time, every complaint from a diver about a twinge or a rash is evidence. I've been in a deposition where an attorney asked about a dive from six years earlier, and we had the records. We won. The obligation to document is the obligation to protect the diver and yourself. One more thing: don't let a client fill your head with talk about 'commercial flexibility.' There are ways to modify decompression for good reason, but 'the barge is on schedule' is not one of them. I've told more than one client that the only person who can authorize a skip-stop is the diver's own body, and that doesn't consult with the project manager. If you feel pressure, the answer is the same every time: no.
Frequently Asked Questions
What are my minimum decompression obligations under OSHA for commercial diving? OSHA 29 CFR 1910 Subpart T doesn't mandate a specific table, but you have to follow a decompression procedure consistent with recognized standards like ADCI or the USN table. For dives deeper than 100 feet, a decompression chamber is required at the dive location. For shallower dives, you still need a workable plan for chamber access if symptoms appear. The obligation is to plan, follow, and document. Can I skip decompression stops if the diver feels fine? No. Skipping stops because the diver feels fine is the fastest route to a hit. The schedule is based on tissue loading, and symptoms can show up hours later. Your obligation is to follow the approved schedule exactly. The diver's state of mind is not a substitute for the table. What if a client pressures me to shorten decompression time? You say no, and you write that refusal in the dive log. No contract incentive is worth a DCS hit or worse. ADCI and IMCA standards place responsibility on the supervisor and the company. If the client wants a shorter stop, you can propose a gas switch planned before the dive, but you never cut stops on a whim. Repeat pressure means the dive stops. Do I need a decompression chamber on site for every commercial air dive? Not every dive. Under OSHA, a chamber is required when you dive deeper than 100 feet or go beyond no-decompression limits. For shallower decompression dives, a chamber must be available within a reasonable travel time. In practice, my crews treat a chamber as mandatory for any dive with planned stops. You don't want to be explaining an unplanned ascent.