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I'm wondering if it is possible to have portable oxygen tanks with medieval era technology? Could it be applied to a horse? Ideally a rider and their horse could ride, even gallop, through smoke filled land for two hours.

A similar question was answered about oxygen cylinders for going underwater. I like the idea of using leather for an airtight container. However, for the top solution in that thread (assuming a human breathes 440 liters of air per 15 minutes), I would need a balloon 3-4 cubic meters in volume to last a human 2 hours. A horse that is breathing hard would need something even bigger, and a balloon at those sizes would be rather awkward to fit on a horse. Is there some way to use compressed air? Does the math change since we are not underwater?

Another solution might be a gas mask to make it through the smoke. The problem I have with this is I don't buy medieval setting people being able to create activated carbon. An assumption in that thread is that the people have modern day knowledge of gas masks, so they can get away with creating the activated carbon. In my setting this feels too advanced, I'd prefer the oxygen tank if possible.

What do you think?

Edit: Fixed the math for 2 hour balloon.

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    $\begingroup$ Tank - or tank, tap, regulator, pipes and demand valve? I take it the question of a pump to pressurise the thing in the first place is for another question (it could be tricky without precision tooling). $\endgroup$ Commented Mar 19, 2020 at 19:45
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    $\begingroup$ It all depends on the specific technical specifications of your intended "oxygen tank". Filling a suitable recipient with air under resonable pressure, one, two, possibly three atmospheres, is perfectly possible with medieval technology. Delivering that compressed air on demand is something else entirely. Not to mention that usable diving cilinders hold air under high pressure, 100 atm or more. On the other hand, "activated carbon" is just a fancy name for finely crushed charcoal; they could definitely make it in the Middle Ages. $\endgroup$
    – AlexP
    Commented Mar 19, 2020 at 20:44
  • $\begingroup$ P.S. Your numeric values are very strange. First, one cubic meter is one thousand liters. Second, 100 liters/minute is ample even for a male athlete at top effort; for a normal human at rest we are speaking of less than 10 L/min. $\endgroup$
    – AlexP
    Commented Mar 19, 2020 at 20:51
  • $\begingroup$ I'm confused by your maths? A Cubic meter has 1000 Litres in it. And a human breaking 440 Litres per minute can last 2 hours? Or 120 minutes? What? $\endgroup$
    – Shadowzee
    Commented Mar 20, 2020 at 0:00
  • $\begingroup$ @AlexP and Shadowzee, thanks for checking my math! I took the 440 value from the under-water cylinder question but didn't realize that was for 15 minutes rather than 1 minute. As for 440 liters to a cubic meter...I was doing some very forbidden math that I would rather not show and forget about...(to be clear, with my sane mind I agree 1 cubic meter holds 1000 liters). $\endgroup$ Commented Mar 20, 2020 at 23:37

2 Answers 2

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Strictly Speaking...

Yes, a gas tank, much like those we see in rescue and hospital use can be constructed using medieval technology. The body of the tank can be cast from any available metal, much like how a bell or a bombard is cast.

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A dinkum on top, cast separately and screwed down into the body, would house a simple pin-hole valve.

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A couple of leather and glass contraptions could serve as the delivery system for man and horse alike. High top hat optional.

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Deal Breaker...

There is just the matter of the obvious spanner in the works that will frustrate your plans. And that is, no one in that time period knew about oxygen, let alone how to destill it from air. In modern times, of course, we can do this electrically, chemically or through cryogenic destillation. While technically, some chemical reactions they could have done in those days produce oxygen, they wouldn't have known it was even there. And even if they knew it was a "different sort of air", they still wouldn't know what its use was and so wouldn't have any idea to put it in the tank in the first place.

But that's okay!!

Happily, your man and horse don't really need pure oxygen to gallivant through smoky, dragon infested lands. All they need is fresh air! And happily, your non-smoky and non-dragon infested lands have plenty of fresh air to put in the tank.

whew!

But wait! There's more!!

Sadly, just when you thought I was going to give your plan the metaphorical green light, I'm going to dash your plans yet again! The technology for compressing the air to get it into the can in the first place is quite new. Literally, mid-19th century.

Conclusion:

Tank = yes
Oxygen = NO
Compressed Air in the tank = NO

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    $\begingroup$ (1) They had bellows for thousands of years before the Middle Ages. (2) Pipe organs are medieval technology, and they use compressed air. ($\leftarrow$ Yes, that's cheating; the "compressed" air is under a very low pressure, 10 millibars or so.) $\endgroup$
    – AlexP
    Commented Mar 19, 2020 at 20:34
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    $\begingroup$ @AlexP -- Yes, they had bellows! Organs are actually ancient tech (hydraulis), but the Byzantines were apparently adept organ builders, exporting them to the West in the 600s and thereafter. Bellows would certainly help filling a soft bag like a balloon or wind chest, but the OP wanted a tank, so a tank I gave him! :D $\endgroup$
    – elemtilas
    Commented Mar 19, 2020 at 21:37
  • $\begingroup$ @AlexP - of course, some organs do operate on higher pressure, up to 250 millibars. $\endgroup$
    – elemtilas
    Commented Mar 19, 2020 at 21:44
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    $\begingroup$ @DanielHicks If you have magic that creates clean air, you should just use that instead. Give the rider and the horse hoods and have the rider cast continuous low level create air inside them. The overpressure will keep smoke and toxic gasses out. Maybe add something to assist in sustaining the magic similar to the computation orbs in Tanya the Evil. Basically if your world differs in some way (has magic to create clean air) you want to show that in use, not to use it in the background to enable a mundane solution. $\endgroup$ Commented Mar 21, 2020 at 0:28
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    $\begingroup$ @VilleNiemi, thanks for the suggestion. One quirk of the magic system I use is that it takes a good amount of concentration, even when using items that empower the magic. Riding a horse and doing magic at the same time would be extremely difficult, especially since my character is going on scouting trips that take weeks at a time, riding for most of the day. Do you think if I showed her stopping the horse and describe her using magic to fill the tank every few hours it would show the magic enough, or still be too mundane? $\endgroup$ Commented Mar 21, 2020 at 15:08
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Alternatively, why not use a miasma rebreather? said the Alchemist

Heating saltpetre (potassium nitrate) releases oxygen and changes into potassium oxide / hydroxide, which absorbs carbon dioxide from exhaled air. No pumps, high pressure plumbing or compressed gas storage required.

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