Hyperbaric Chambers on Site: When They Are Required

By Dutch Hollander, Offshore diving superintendent. Reviewed by Dana Whitcombe, technical reviewer.

Underwater Inspection | Commercial Diving Contractors Alabama I've had this conversation a hundred times. A client standing on the back deck of a dive boat, pointing at a steel tube that looks like a submarine's escape pod. 'You're telling me we can't do a 110-foot dive without dragging that thing along?' That thing was a hyperbaric chamber, and the question was worth taking seriously. Over nineteen years in the Gulf, I've seen chambers save careers and, in two cases I know of, lives. They're not paperwork. They're the difference between treating a bend on the spot and flying a guy ashore with a ticking clock. So when are they actually required? It's not a matter of opinion. It's written down. Let me walk you through what I've got to plan around.

The regs draw a line at 100 fsw

OSHA 29 CFR 1910.421 is the one that matters for us in the U.S. Gulf. It says a decompression chamber has to be on site for any dive deeper than 100 feet of sea water, or any dive that has a decompression stop. That's not a suggestion. I've had to cancel a job because the client didn't want to pay the freight on a chamber. Cancelled it. The regs don't care about your schedule. But here's the thing—the chamber requirement is just the start. You need a properly trained crew to run it, a medical gas supply, and a tender who knows how to lock through. I've walked off jobs where the chamber was on the deck but the operator couldn't tell me the last time it was hydrostatically tested. That's a red flag. The chamber isn't a decorative ornament.

A decompression chamber isn't the same as a recompression chamber

In the field, people say the words like they're interchangeable. They're not. A decompression chamber is the big pot you use for surface decompression, taking a diver out of the water on a schedule and letting him offgas in comfort. A recompression chamber is the same piece of hardware on a different mission—treating a bend. Most chambers do both. But when we're talking compliance, the regs call it a decompression chamber. The distinction matters because when you're checking your paperwork, you'll see 'decompression chamber' in the reg, not 'recompression chamber.' I learned that the hard way during an audit about five years ago. The chamber was there, the cert was there, but the label on the maintenance log said 'recompression chamber.' The inspector took his time, but the log was fine. The point is, know the vocabulary.

Depth and bottom time are the triggers

It's not just depth. A 90-foot dive with 40 minutes of bottom time can put you into a decompression obligation with the U.S. Navy tables, call it a 10-minute stop. That means a chamber is required, even though you never made it to 100 fsw. The trigger is the decompression stop, not just the depth. So I plan every dive profile against the tables before the first pair of fins goes in. Everyone in the water gets a profile. We use air for bounce diving, and I've got the Navy 33 tables laminated on the wall of my office. For heliox or trimix, it's different, but on typical IRM scopes, air is the mix. I make the dive planner show me the table and the chamber requirement before we leave the dock. If he can't, we're not leaving.

Saturation changes the math

When you're living in saturation, the chamber isn't a requirement, it's the habitat. It's your living room, your mess hall, your bunk. I've run sat jobs where the chamber sits on the back of a vessel for weeks. But that's not what we do on most IRM scopes. Most of us are bounce divers. Still, you'd be surprised how many times I've had to explain to a pipeline foreman that a 120-foot air dive with a table-decompression profile needs a chamber on the deck. He doesn't need to understand the physics. He needs to know I'm not sending my guys into the water until that chamber's on the pin. On the other hand, if you're planning a saturation dive, say 200 fsw for 20 days, you're not just dealing with a chamber. You've got a full deck decompression unit, plus all the life support gear, a bell, and a crew that lives in a decompression schedule. The chamber is the least of it. But for the record, a sat system is just a hyperbaric complex on a bigger scale.

The practical realities of getting a chamber on site

Getting a chamber isn't like ordering a pizza. In the Gulf, you're normally talking about a 4- or 6-man double-lock chamber, like a Perry or a Sechrist. It needs a compressor, a supply of breathing gas, a certified chamber operator, and room on the aft deck. That can eat 20 feet of deck space, give or take, and a few tons of payload. It's a logistical headache, and it's cheaper than the alternative. I had a client try to save money by renting a chamber that was too small for the crew. We were running four divers, and the chamber was rated for three. It passed all the checks, but there was no way to lock out the bent diver and keep the tender in. We swapped it. It cost us two days, but you don't compromise on the box that can save a man's life. The rental quote is usually a daily rate, plus mobilization, and it's not cheap. But it's far cheaper than a life.

Frequently Asked Questions

What depth requires a decompression chamber? Under OSHA 29 CFR 1910.421, any dive deeper than 100 fsw, or any dive with a decompression stop, requires a decompression chamber at the dive site. I treat 100 fsw as the hard line, and I check the tables for anything below that if the profile's aggressive. Is a recompression chamber the same thing as a decompression chamber? In the Gulf, we use the same piece of equipment for both. But the regs call it a decompression chamber. Recompression is the treatment side. For compliance, you need a chamber that can do both. Can I use a chamber on a nearby platform instead of having my own? No. The regs say the chamber has to be at the dive site, ready to go. I've had clients ask if the chamber on a platform half a mile away counts. It doesn't. It has to be on your vessel or rig, or at the location where the dive is taking place. Do saturation dives always require a chamber? Saturation diving by definition involves a pressurized chamber for the divers to live in, so yes. The chamber isn't an extra for sat work; it's the system itself. For bounce diving, the requirement kicks in at 100 fsw or a decompression stop.