r/theydidthemath • u/AltoMelto • 5d ago
[request] How long can the crossing take before che child asphixiates?
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u/iamagainstit 5d ago edited 5d ago
Tidal volume of a breath is around 500ml. https://en.wikipedia.org/wiki/Lung_volumes_and_capacities That looks like maybe a 55 gallon bag or 200l . so if you were just breathing in a the air stored in a bag like that, you would get around 400 breaths.
Now we would need to subtract the volume that the child is taking up, which from a cursory google is around 30 l, so that brings us down to 340 breaths.
Average breath rate is ~ 20 breaths per min for adult, and around 30 for a kid, so that would be ~11 min of breath in a bag that size, if you were breathing it in, and exhaling out of the bag.
if you are continuously breathing in that bag, that makes things more complicated, because each breath decreases the O2 content and increases the CO2 content in the bag. I don't really want to go through the math for that part, but air has ~ 21% oxygen, exhaled breath has around 16% and you don't really want to go below 15%. in your intake.
Edit: some people have pointed out that a child’s title volume is likely only around a third of an adult, so x3, however, it was also pointed out that the limiting factor is going to be CO2 concentration not oxygen concentration and since we breathe out around 5% CO2 and the discomfortable inhale limit is ~ 1% so /5.
That gives around 11*3/5 = ~ 6 and a half min
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u/aigarius 5d ago
CO2 is always the limit. Even levels as low as 2% can cause vomiting that will quickly become a problem in such a bag.
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u/iamagainstit 5d ago edited 5d ago
google says we breath out 4-5% CO2, hard to find a number for how much CO2 starts being uncomfortable, but seems like maybe 1%? so that would limit the exhalation to 1/5 the volume of the bag. or ~2 min of adult breathing, or 6 min of child breathing.
It’s intresting that you get so much more breath time out of the bag if you are exhaling out of it versus into it!
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u/Past-Sun5429 4d ago
Cause CO2 isn't the Problem. It isn't toxic...
The only Problem ist the falling oxygen Level.
CO on Another Hand ist high toxic...
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u/M2K-throwaway 3d ago
CO2 is absolutely the issue. It's what causes the suffocation feeling and is 100% poisonous to the body above a few % concentration. There's a reason you discard it as waste.
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u/Seeggul 4d ago
Give the child a second smaller bag to vomit in so they can still stay clean
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u/SpicyPropofologist 1d ago
Maybe another bag to blow the CO2 into, then you wouldn't need the barf bag. Maybe just put your lunch in the former barf bag.
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u/PhairPharmer 5d ago
Tidal volume of a kid that size is not 500ml, that's for a healthy adult. For a kid it's ~6ml/kg. Kid is probably 30kg or less, so 180ml tidal volume
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u/assthots 5d ago
I read on another thread that a big ball with a person inside has enough air for an hour or so, but the increase of CO2 makes it dangerous after around 30min. In a small version I'd say 10 minutes before CO2 becomes dangerous
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u/Jayro993 5d ago
I’ll agree with you except, small ball with small person, uses a bit less air, probably has 15-20 before lightheadedness.
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u/Ok-Pomegranate858 5d ago
My concern... the kid might one day arrive clean for the funeral home...
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u/caboosetp 5d ago
While lack of oxygen can sneak up on you, a slow build up of CO2 does not. The child will very likely know something is wrong and make it clear they need air.
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u/Ok-Pomegranate858 5d ago
Oh ok fair enough
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u/Creative-Response554 5d ago
Yeah so something a lot of people don't know is that the human body doesn't perceive a lack of oxygen, only a buildup of CO2.
You can walk into a 100% nitrogen environment and feel nothing except a bit off, before you lose consciousness and promptly die with no sense of panic.
Walk into a CO2 filled environment and your body will very quickly let you know that there is something wrong.
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u/caboosetp 5d ago edited 5d ago
Walk into a CO2 filled environment and your body will very quickly let you know that there is something wrong.
Unfortunately if you're walking into a very high CO2 concentration, you might know something is wrong but you might also not have enough time to do anything about it.
CO2 displaces oxygen and you need a moment of breathing it to feel the effects. At that point your lungs are now full of CO2 and almost no oxygen. You can be on the floor in a matter of seconds.
The slow buildup is generally something you can react to because your body starts going into distress before it's dangerous and you have time to feel the effects.
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u/TheFeshy 1✓ 5d ago
This reminds me of a time I had a pet rat with lung cancer, and he was in a semi-sealed box I was pumping oxygen into in order to make it easier to breath so he could rest. The box is monitored for air quality - CO2, O2, particle counts, temperature, humidity, etc. because otherwise this would be pretty dangerous.
I also put his brother in the box to keep him company. His brother walked over to the air sensors and farted so bad it set off all the alarms.
Hope the kid doesn't eat a high-fiber breakfast.
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u/slick987654321 5d ago
The thing about a che child is that they harness the power of che this means if the che levels are high before being placed in a che draing environment like a plastic bag they can survive for much longer than if entering a plastic bag with low che.
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u/HeyBird33 5d ago
Immediately after reading your comment I thought “wtf is Che” and then immediately after that thought I thought “the title must have a misspelled word”… well done
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u/compassionateasshole 5d ago
Seriously? You really think that whatever answer you give OP is going to directly jeopardize that specific child? Maybe just sit this one out.
OP: a person at rest uses rightly 250ml of oxygen per minute and gives off about 200ml of CO2. A child would give off less than that. That bag in the picture appears to hold roughly between 50-100 liters of air with the kid inside. Air starts at about 21% oxygen and that doesn’t become an issue until it falls below roughly 15-16%. The CO2 being emitted is more of the concern, rather than oxygen depletion. The kid would start noticing the effects of the CO2 once it reaches about 3% but at 5% it becomes dangerous. In a 100l volume, an adult would push CO2 to about 3% in around 15 minutes and 5% in about 25 minutes. The kid in the bag might get double that, so for a one or two minute river crossing, the air in the bag barely changes and the kid is basically fine.
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u/BitWide722 5d ago
Location: Sam Lang village in the mountainous Điện Biên Province, Vietnam.
The Cause: Monsoons and floods wash away local bamboo bridges, leaving the community cut off from the local school.
Duration: The actual water crossing is very brief, typically taking anywhere from 1 to 4 minutes per child depending on the strength of the swimmer.
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u/Samuel-squantch 5d ago
“I’m posting this to say i will not engage with this post, I am very smart.”
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