Oxygen Systems and Oxygen Administration
Different O2 Systems
There are different oxygen systems, and they deliver very different amounts of oxygen. For us, only one goal matters: the highest possible concentration. Here are the systems you’ll find most often at dive centers and in emergency kits.
1. Constant Flow with Simple Mask
Oxygen flows continuously, and ambient air mixes in with every breath. That’s great for someone who just needs a bit more oxygen—but not enough for us: often only around 35% oxygen actually reaches the person. Not the mask of first choice.
2. Constant Flow with Reservoir Bag
A small bag fills with oxygen; you breathe in from the bag and exhale through a valve. This achieves concentrations of around 90%. Many dive centers carry these masks in their kits.
- Setting: 15 liters per minute. At rest, we breathe about 6–9 liters per minute, and significantly more when agitated—and that full amount needs to be available.
- Don’t let the flow be turned down to 2–3 liters just because that’s standard for other emergencies.
- This system is also well suited for people who are breathing only weakly.
3. Demand Valve
A demand valve works like a dive regulator: oxygen only flows when you inhale, and exhaled air escapes outward. This means the person breathes almost pure oxygen, and only as much is used as they actually breathe.
- The most efficient option—the highest concentration, with economical consumption.
- Only for patients breathing normally. Anyone breathing only weakly is better off with the reservoir mask.
- A regular regulator on an oxygen cylinder serves the same purpose. But then you need to block the nose—otherwise you unknowingly breathe in air too: pinch the nose (the gentlest method), use a freediving nose clip, or in a pinch, a not-too-tight clothespin.
- A mask that also covers the nose and seals well solves the problem on its own.
4. Wenoll System
A kind of rebreather for oxygen: you exhale into a breathing bag, soda lime filters out the CO₂, and only as much oxygen is added as the body consumes.
- At rest, the body consumes significantly less than one liter of oxygen per minute—compared to a 15-liter flow rate. Small amounts last a very long time, even for several people.
- A bit more complicated to use: you need practice and need to know what connects where.
- Expensive to purchase—but very valuable in remote areas without resupply.
5. Closed-Circuit Rebreather (CCR)
Every rebreather works on the same basic principle as a Wenoll system: CO₂ is filtered out, oxygen is added. If you feed in only oxygen, it delivers practically unlimited, nearly pure oxygen (you never quite reach 100%). The requirement: you need to know how to operate the device. That’s not a reason to buy a rebreather for first aid—but it’s a nice bonus argument.
From kit to oxygen administration
An oxygen kit only helps if its contents match up and are ready to use. So take a calm look through your kit: What connections are there? Which mask goes where? Is the regulator already fitted? Do you need a key to open it—and is it in the kit?
The exact setup depends on your equipment. The basic process is similar for many systems.
1. Create a safe setup
Secure the cylinder so it can’t tip over or roll away. Keep cigarettes, open flames, oil, and grease away. Oxygen doesn’t burn itself, but it can greatly intensify a fire.
Work with clean hands and clean connections. Don’t use lubricants or improvised adapters.
2. Connect the cylinder and regulator
The regulator reduces the high cylinder pressure to the system’s working pressure. If it isn’t fitted yet, first check that the connection and the required seal match and are undamaged.
Fit it according to the manufacturer’s instructions. Some connections are tightened by hand; others require a specific tool. You can’t force a wrong connection to fit.
If the regulator is already fitted, you don’t need to remove it again for every use.
3. Use the correct outlet
On a multifunction regulator, different outlets may be available:
Constant Flow: This is where the thin oxygen hose for a reservoir-bag mask is connected. You set the amount on the flow regulator.
Demand: The demand valve is supplied via the designated pressure hose and connection. It delivers oxygen when you inhale. The liters-per-minute setting on the Constant Flow outlet does not control this connection.
This is a good moment to look into your kit: Can you reliably tell the two connections apart?
4. Open slowly and check
Open the cylinder valve slowly according to the equipment instructions. Check the cylinder pressure and listen for unusual hissing or other signs of leaks.
A pressurized connection is not loosened. If something isn’t sealed, close the cylinder and depressurize the system as instructed before checking the connection.
5. Prepare the reservoir mask
Connect the hose to the Constant Flow outlet and to the mask. For the non-rebreather mask described here, we start at 15 liters per minute; also follow the specifications for your model.
Let the reservoir bag fill before putting the mask on. Briefly explain to the person what you’re doing and ask for their consent. Fit the mask so it seals well around the mouth and nose.
Watch the bag while they breathe: it must not collapse completely on inhalation. If it does, check flow, cylinder pressure, and the hose for faults or kinks. Depending on breathing demand and equipment, the flow may need to be increased.
A mask on the face is not proof that enough oxygen is actually getting through.
6. Prepare the demand valve
Connect the demand valve, pressure hose, and the appropriate mask according to the equipment instructions. Check function in the way specified for your model.
The person must be able to trigger the valve with their own inhalation. Make sure the mask fits well and that they can breathe through it comfortably.
If triggering it is too strenuous, the reservoir mask may be more suitable. If breathing becomes inadequate overall, switching oxygen masks is not enough.
7. Stay with the person
Monitor breathing, responsiveness, and how well they tolerate the mask. Keep checking the oxygen supply as well.
If there is nausea or vomiting, the mask must be removable quickly. That’s exactly why medical masks are transparent: you can see what’s changing underneath.
If the person becomes unconscious or is no longer breathing normally, the relevant first-aid and resuscitation measures take priority. A reservoir mask and a pure demand valve do not provide ventilation.
Now it’s your turn
In the game, you bring the oxygen from the kit to the person. After that, it’s worth doing the same process with your real system: find the connections, assemble it, check function, and make it ready for use again.
The game helps you understand the sequence. You learn and practice the hands-on steps on the actual equipment.
How Do I Get the O2 Ready for Use?
Try out in a small exercise how to get oxygen from the kit to the patient.
How long will the cylinder last?
A full cylinder can be empty faster than you think. For Constant Flow, you can easily estimate the approximate duration:
Cylinder volume in liters × pressure in bar ÷ flow in liters per minute
A 2-liter cylinder at 200 bar contains approximately 400 liters of oxygen. At 15 liters per minute, that’s theoretically just under 27 minutes. In practice, plan for less: not all contents are usable, and you need a reserve.
With a demand valve, consumption depends on the person’s breathing and any leaks. That’s why the duration isn’t a fixed number.
For your planning, what matters is the time until a reliable continued oxygen supply is secured. How far away is the dive site? How long is the drive back? What happens if two people need oxygen?
Clarify in advance where additional oxygen is available. If the supply is running low during use, arrange a refill early and coordinate the next steps with EMS or the diving medicine hotline.
Ready for the next call-out
After handover, the kit is not ready for use again yet.
Close the cylinder and depressurize the system according to the equipment instructions. Replace used single-use items and reprocess reusable parts according to the manufacturer’s specifications. Have the cylinder refilled, check function, and restock missing items.
As a team, decide who is responsible for this. A short entry with date and name prevents everyone from assuming someone else has already taken care of it.
Before the next trip, check supply, completeness, and function again.
Better a Few Times Too Early Than Once Too Late
The earlier someone receives oxygen after a diving accident, the more likely the outcome will be mild. Right at the start, shortly after surfacing, the bubbles are only just forming. If we intervene then, we can interrupt the whole cascade. The longer you wait, the less effective the oxygen can be.
Still, oxygen administration is often delayed. The reasons:
- Stigma: Someone who has a problem after diving is often asked first what they did wrong—drank too little? Went too deep? Yet the person has often done nothing wrong at all. But because people are always looking for mistakes, many don’t dare say that something is wrong.
- Denial: Nobody likes to admit that something isn’t right right now—especially not after a great dive.
- The dive center’s or instructor’s reputation: “That can’t be right, we had two completely normal dives with clean profiles.” That’s simply wrong. Even if everything was done correctly, something can still happen—that’s exactly why we carry oxygen.
If you’re asking yourself whether now is the moment to get the oxygen: get it.
- You can’t cause any harm with it.
- If it turns out not to have been DCS after all, that’s fine too.
- Observing what happens while breathing oxygen can help clear up doubts—for example, if skin blotches visibly recede. But “can help” doesn’t mean “proves”: in half an hour of oxygen, half an hour also passes during which symptoms can ease on their own. Discuss the next steps with the hotline—even if the symptoms have disappeared.
Case Study: Giving Oxygen
You know the systems and how to prepare them. The case trainer is about applying that knowledge in different situations: give oxygen or gather more information first? Which mask fits? And what changes your decision?
You’ll get an explanation for each decision. Make sure to also work through the cases where you’re initially unsure—that’s exactly what they’re there for.
Your Punkfish O2 Provider Update
Are you already practically trained in oxygen administration, have access to an O2 system, and practice its use regularly? Then you can refresh your knowledge with our online course.
For the Punkfish O2 Provider Update, you confirm your previous practical experience and regular practice. Upon completion of the course requirements, you will receive your Punkfish Update Diploma.
If you lack practical experience, you start with the theory. You then practice using the O2 system with us or with a suitable local provider. If you don’t have a contact person for this yet, we will look for an option together.
If you have already booked the course, you can find the overview of your course progress and the final exam here:
