By Harry Keller
Former ETCJ Science Editor
& President of SmartScience
Spending two weeks in a cave that has been sealed off by water is no one’s idea of fun. There’s no food but plenty of water. This cave portion appears to be fairly large, large enough to have plenty of air for a long stay, but that air is running out.
Thirteen people, twelve of them children, are stuck and isolated under very dangerous circumstances. They face several perils: oxygen, carbon dioxide, food, and even waste treatment.
Detailed map of the Tham Luang cave system provided by BBC News.
What happens when someone seals you into a box? You use up the oxygen there, turning it one-to-one into carbon dioxide. That’s what all animals do. Even plants do it when there’s no sunlight. It’s called respiration. In that box, you will rapidly drop the oxygen level to below the 16% that we must have to function normally, and that’s 5% below the usual 21% we are used to.
Long before you reach 16% oxygen, you will raise the level of carbon dioxide (CO2) from 0.04% up to 1%. At that level, you will feel the effects of hypercapnia as your blood pH drops into an area that prevents many of your cellular processes from functioning properly. First, you may feel a bit woozy, but soon you will lose consciousness and then die.
The same thing might happen in a cave, but that Thai cave has a silver lining. The same thing that trapped them there has saved them from hypercapnia — the water. It’s flowing water, and CO2 dissolves fairly readily in water and is carried off away from the trapped children and coach. Unfortunately, the incoming water does not bring enough oxygen to replace what they are losing by breathing.
An average person uses up about 550 liters of oxygen daily. According to reports, the 13 trapped people are now down to 15% oxygen in their chamber. If we assume that each small child is equal to about one-half of an adult, then the oxygen consumption should be about seven times 500 (they aren’t very active) or about 3,500 liters daily. After two weeks, a drop of 6% suggests that the total volume of the cave is very roughly 60,000 liters. It also suggests that one-half of one percent of oxygen is being consumed each day.
If they do not get oxygen soon, they will lose consciousness and be unable to help their rescuers get them out of the cave through the gauntlet of a lightless and treacherous, many-hours-long passage to safety. Because they are, in effect, adapting to lower oxygen concentrations slowly over time, they may last longer, but you shouldn’t expect them to survive oxygen levels below 8%. That’s what you would experience above the summit of Mount Everest.
You cannot get rid of 6% of the air in the cave chamber without consequences. The air pressure must be declining. At the same time, the water level, pushed by outside air pressure, must be rising. Fortunately, neither of these effects should impact the survival of those in that cave.
An optimistic estimate of how long the children will survive without more oxygen comes out to maybe two more weeks. By then, they would be unconscious and severely affected by a lack of calories to maintain their body functions. As numerous news articles have explained, more rains such as the one that trapped them could come and raise the water above their small island in the cave before those two weeks elapse.
We are witnessing a true cliff-hanger in real life as the efforts of a great many people are pitted against the realities of the situation and the scientific and engineering problems that must be overcome to rescue those children. As John Adsit has so eloquently written, even with food and air, we may not successfully remove all of those children to safety because of the extreme hazards of the hours-long trip to the outside world.
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Related article by Keller: Three Most Important Takeaways from the Thai Cave Rescue
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Educational Technology and Change Journal 
Things are looking up in that Thai cave. Reports tell us that those boys have oxygen and that the O2 levels are up. They must also have some food now as the authorities are considering keeping them in the cave for months until the waters subside but are still trying to get them out sooner.
Attempts to drill down to the cave have failed so far. Drilling some 800 meters or so to hit a target just a few meters wide is hard, and they haven’t yet drilled more than half of that depth.
Elon Musk has the wildest idea yet. Push long, flexible tubes through the flooded parts and inflate them so that the soccer team can walk through. Of course, the members would have to pass through an airlock to enter and leave. The tubes would have to be made of a material that would not be punctured by sharp rocks and would be very flexible to bend around the twists and turns of the cave passages. Now that time is less of a problem than before, this solution may be used on just one or two difficult parts of the passage with the others being traversed with SCUBA gear.
Science takes a back seat now to engineering, and Musk certainly is a highly creative engineer. He has the advantage of being able to think of solutions without monetary constraints.
The Thai cave escapade continues to lurch from one challenge to another. The upcoming rain may flood the cave so much as to drown its occupants according to one report.
If the chamber in question is sealed, how can that happen? There must be cracks small enough to let the air out but not large enough for any rescue purpose. This changes my earlier ideas about the water level moving up as the air is removed by CO2 dissolving in the water. It does suggest that spraying the ceiling of the cave with a sealant could prevent the drowning, but the sealant vapors would probably be harmful, and they certainly do not have the means to ventilate that cave chamber.
The world is watching as this drama continues to unfold. It’s almost guaranteed that some more life will be lost and a miracle if not.
Amateurs should not go exploring caves. The dangers are too many and the benefit too small.
Now that 2/3 of the trapped soccer team has been rescued, the full extent of the difficulties is beginning to sink in. Each rescued boy was accompanied by two divers. That’s how treacherous and challenging this rescue effort has been.
In the end, it has been around-the-clock pumping out of water and old-fashioned diving skills rather than clever technology that has done the trick. A bit of a break with the weather didn’t hurt much either.
There are few details about much of the operation, but it appears that a mile-long air hose was the most crucial feature for keeping the trapped team alive. The water pump lowered the water level, making the rescue somewhat less arduous. Beyond that, it has been the skill and courage of the divers that has brought success thus far. We can only hope that the remaining four trapped people will come out unharmed too.
Wow! They’re out! Nineteen divers worked for hours to bring the last five team members to safety in the most daunting conditions imaginable.
I find it quite wonderful that this rescue effort was accomplished with existing and somewhat old technology. It was mostly grit on the part of the rescue team that made this possible. People can do what they really desire to do. They can overcome, especially if they work together.
Congratulations to all of those involved.