Re:British divers make contact with missing Thai football team
by chiasmic on Tuesday July 03, 2018 @08:27AM
(#17449562)
Even if the cave was closed from a gaseous perspective, there is flowing water. Gases dissolve in water, although not necessarily very quickly. Would the flow of water allow for CO2 to be removed from the space given a sufficiently large surface area?
Re:British divers make contact with missing Thai football team
by azernik on Tuesday July 03, 2018 @10:05AM
(#17450245)
Generally caves have elevated CO2 levels not because of human respiration, but because of outgassing - they're generally eroded out of carbonate minerals, and so the water flowing in carries CO2 inside at higher concentrations than the outside world. The smaller the subsystem the human is isolated in, the faster they perturb that equilibrium toward an even higher CO2 level.
The ESA, of all groups, has a pretty good write-up on this: http://blogs.esa.int/caves/2014/11/19/the-science-of-caves-e... They use cave exploration for astronaut team-building, process/workflow training, and acculturation.
Re:British divers make contact with missing Thai football team
by gehwartzen on Tuesday July 03, 2018 @11:22PM
(#17455088)
The article's reference to the boys faces being lit by torchlight had me pretty startled (considering the implications of fire in an at least partially sealed cave) until I realized the story was in The Guardian!
Most cave systems are relatively permeable. Even if you can't see a route out, there are likely to be paths for air movement.
The immediate threat is the accumulation of carbon dioxide rather than a deficit of oxygen. Fresh air is about 0.04% CO2, but most caves have ambient CO2 levels of over 1% and some as high as 6%. You'll start feeling quite unwell above 4%, violently ill above 7% and there's a risk of seizures, unconsciousness and death above 10%. Normal air is about 21% oxygen, you can cope perfectly well on about 16% oxygen and survive on as little as 10% oxygen.
The boys seem alert and in reasonably good spirits, so I'd say that the air in their section of the cave is fairly good.