How To Spot Bad Scuba Journalism
Oxygen.
Divers running out of oxygen.
If you read a news article about a scuba accident, and the cause of the accident is stated as “a diver ran out of oxygen” then you know that the journalist who wrote the article has absolutely no clue about scuba diving and the rest of the article might be just as non-factual as this statement. With a few rare exceptions, scuba divers don’t breathe oxygen. But this claim is surprisingly common, almost the majority of non-specialized news sources talk about “running out of oxygen” when discussing scuba accidents.
Here is an example from a randomly chosen local news outlet in Kansas, US:
And of course CNN, one the world’s biggest peddlers of weak and biased journalism, can’t be left out when it comes to bad scuba accident reporting: “Then my tank ran out of oxygen.”
And here is another one with no oxygen in a cave.
These are just three of many examples. Pay attention the next time a diving accident is reported: The chances are very good that an empty oxygen tank was supposedly the reason.
Just to be sure: My condolences to the friends & families of everyone who died. I am of course NOT making fun of them, but of the hapless journalists reporting on the accidents.
What Scuba Divers Really Breathe
Scuba divers almost always breathe compressed air. A compressor packs the air into an aluminum or steel scuba tank, and a regulator reduces the pressure of the air to the ambient water pressure. In this way, the breathing gas going into a diver’s lungs is at the same pressure as the outside pressure. This keeps the diver’s lungs from overinflating or compressing. A scuba diver can breathe comfortably under water: breathing regular, normal, conventional, atmospheric air. Not oxygen. Oxygen makes up only ~21% of atmospheric air, with nitrogen ~79% and trace gases less than one percent.
Rare Exceptions
There are some exceptions: the slightly specialized scuba breathing gas nitrox is a air enriched with additional oxygen. Typically, nitrox contains 32% oxygen (versus 21% in air). This allows divers to stay at moderate depth longer. Still, divers are then breathing enriched air, not oxygen.
Below: Almost a scuba accident, but no one ran out of oxygen:
Also, technical divers sometimes actually breathe pure (1–&) oxygen, at the end of deep dives, and only once they are at a depth of 6 meters or shallower. This allows them to quickly complete their decompression stops which they need to ascend without getting the bends. This is a really specialized kind of diving, with much less than a percent of scuba dives being such technical dives. A technical diver who breathes oxygen at 6 meters and runs out can easily surface (it’s only 6 meters to get there); hence, “running out of oxygen” is barely ever a cause of death in such rarely done technical dives, either.
So, why do divers generally not breathe pure oxygen (as alleged by CNN and others)? Oxygen becomes toxic when breathed at higher pressures. It causes a loss of consciousness and convulsions. That’s the case above about 1.6 bar of oxygen partial pressure. The partial pressure simply is the fraction of oxygen in a breathing gas (1.0, or 100% in the case of pure oxygen) multiplied by the ambient pressure under water. The ambient pressure increases from 1 bar at sea level, above the water, with a rate of 1 extra bar every 10 meters below the surface. This means that at 10 meters the ambient pressure is 2 bar, at 20 meters 3 bar, and so on. At 6 meters, the limit for breathing oxygen safely, the ambient pressure is 1.6.
Hence, diving deeper than 6 meters and breathing oxygen – with partial pressure of above 1.6 (1.0 fraction of oxygen X 1.6 bar ambient pressure – 1.6) – will generally kill ya. Hence, regular scuba divers breathe air, not oxygen.
Why Is this Reporting A Problem?
Number one, it’s just wrong.
It’s also a warning sign. I know a lot about scuba diving, and reading all these reports about “running out of oxygen” I immediately realize that the journalist who wrote the article had no clue about the topic he or she wrote about.
Now, I don’t know much about aviation, steel manufacturing, skydiving or kidney diseases. But, given my experience with a complete lack of even very basic knowledge about scuba, I have to assume that the reporting about these other topics isn’t much better. It’s good to have people write about topics – especially for a general audience – who in fact are trained and knowledgeable about a topic. Can’t CNN and friends afford to pay such people, or don’t they care?
