breathing aparatus

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breathing aparatus

Postby crit11393 » Wed Nov 26, 2014 10:13 pm

So, I need my character to make a rather longish trip (let's say, 8 – 10 hours) in some sort of environmental suit with contained oxygen. Just how heavy are the air tanks going to be for something like that? I have other options including plugging the suit into the reserves of the vehicle – but at some point she will need to leave the vehicle.

Suggestions? Hard information (possibly with links to information on the Internet)?
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Re: breathing aparatus

Postby crit30275 » Sun Nov 30, 2014 4:03 am

Current suit scuba tech removes the exhaled C02 and reuses exhaled O2, in that mode looking on line I think a 20 kg tank contains about two hours of air with a re-breather. Its not stated clearly that I can find. So that may be off.

But if the suit is capable of converting the exhaled CO2 in to C and O2 then the limit should be the power supply for the converter, battery life. Suit weight would be whatever you want it to be for that.
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Re: breathing aparatus

Postby crit19292 » Sun Nov 30, 2014 12:07 pm

Depth is also a major consideration for air time.

Let me however say that if you really want to know (and you should if you really want to do the story) then you will put in the time doing the research. It is better if you do, as you would be surprised at all the other trivial details you will also pick up in the process. Learning is more than gaining facts, it is also gaining an interest in something new. Do all you can to find out about scuba, as it will make you, and not just your story, better.
I will not deny myself having my opinions.
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Re: breathing aparatus

Postby crit11393 » Sun Nov 30, 2014 10:12 pm

Thanks for the input.
Depth isn't an issue. The issue is an atmosphere that is getting so cold dry ice is forming and the air exchange apparatus is shutting down so the character shifts to tanks. And yes I'm a big believer in research but I like pointers in what direction to go. My googling wasn't working probably as I don't know enough to know what I'm looking for.
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Re: breathing aparatus

Postby crit32029 » Tue Jan 26, 2016 6:04 pm

crit11393 wrote:Thanks for the input.
Depth isn't an issue. The issue is an atmosphere that is getting so cold dry ice is forming and the air exchange apparatus is shutting down so the character shifts to tanks. And yes I'm a big believer in research but I like pointers in what direction to go. My googling wasn't working probably as I don't know enough to know what I'm looking for.


Saying depth is not a major consideration isn't exactly accurate. It's the atmospheric pressure that affects the volume of the gases contained inside scuba tanks. If you fill a tank with 1 liter of air at the surface (where the atmospheric pressure is by definition 1bar), that volume will decrease as you go deeper due to increasing pressure. Less volume equals less breathing time available.

So, the real question is, what's your environment's atmospheric pressure like?
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Re: breathing aparatus

Postby crit32856 » Fri Oct 28, 2016 1:34 pm

Things to consider:

How big is your character and what are? Oxygen consumption per hour varies incredibly depending on activity level. "the oxygen cost of sitting quietly, equivalent to 3.5 ml/kg/min." -- Wikipedia, "Metabolic Equivalent", found using Bing and the search term "oxygen consumption per hour resting"

So let's say your character weighs 70Kg (154 pounds). Sitting, they consume 70*60*3.5ml = 14.7 liters of oxygen (at standard temperature and pressure (STO), 1 atmosphere, 70F) per hour. Oxygen's density is 1.429 g/L (Wikipedia, "Oxygen") at STP, so that's 21 grams of oxygen an hour, or 200 grams (about half a pound) in ten hours. It turns out, you can almost buy the product you need today - http://www.medicaldepartmentstore.com/H ... p/h850.htm - a 5.6 pound unit that holds 2 pounds of liquid oxygen in a dewar bottle. All you need, then, is a CO2 scubber and you're good to go - if the character is just sitting and you don't waste oxygen.

Bing or google, either way, you can find what you need to know with creative searching.
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