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I'm working on a short sci-fi game and I'm curious about how the effects of a hull breach in a confined area play out. For perspective, let's say a very confined space of 100 cubic feet of normal, livable atmosphere, with one person inside wearing regular clothes. If it takes 30 minutes for the atmosphere to fully escape, what would happen over that time span?

I've read quite a bit about the effects of vacuum on people and water, etc., but it's always described as if there is immediately no pressure. One second you're fine and the next, you're in space. How things play out as a vacuum builds over a period of time, I have not found anything of substance.

Here are some of my basic questions, and it doesn't need to be an exact time stamps, just an approximation [30:00, 27:00, 24:00, 21:00...]

1.) When would someone become confused? When would they have laboured breath? When would they pass out?

2.) Would it get cold? Would condensation ever form/freeze on surfaces during this time? Would a person get hypothermia?

3.) Would they feel their tongue boil before they pass out? Would vision be affected?

4.) Would they experience swelling of hands and face? Would it be hard to bend their joints and grasp things?

5.) What size of hole would deplete the atmosphere in 30 minutes? Would you hear a whistling?

6.) If noise was occurring from any source, would it become more silent as time goes on... or just stop all together at some point?

7.) Bonus question: If the person had a regular oxygen mask (like a fighter pilot), how would it change the way this plays out? Can they even use the mask effectively after a certain period of time?

Just looking for perspective mostly (there are so many factors at play) and feel free to bring attention to things that I might not have thought of. I figured this was probably the best place to ask a question like this. The alternative is that I use "movie logic" to write this scenario and I'd rather not go there. ;-) Thank you.

Update (4/27/2023):

Wow! Thank you all so much for your input thus far. I'll be going through the suggestions and piecing together a proposed time line of medical and environmental variables soon and update this question with that for your opinion and critique.

Note: I refrained from delving into the specifics of the scenario for fear that it might be moved to one of the writing exchange sections. However, some here have questioned about sensor alarms and such so I'll provide a little more context for the curious, but let's keep the feedback centered on the medical and science side as much as possible.

Basically, it's a puzzle/escape room scenario. You're a pilot in a small, short-range, single cockpit star-fighter. You open your eyes to an alarm describing that you have X minutes until life support fails. Your ship is badly damaged and spinning uncomfortably though debris and wreckage. Not all thrusters or systems work. Evidence of a massive battle is all around. So yes, the alarm is happening and you've just come to from what can only be a massive impact in the time leading up to now. I envisioned a hull breach to be the catalyst for the timer.

I'd like an engaged, panicked pilot who succumbs after 20 minutes, if they can't reach safety in time. Being a pilot, in a rudimentary ship (the sudden war forced massive manufacturing efforts to get war ships in space ASAP), I figured he would have an oxygen mask and a regular jumpsuit. Because it's a game of choice, you can choose not to put the mask on and deal with the consequences (why I needed that information). However, the oxygen mask does seem integral in prolonging the available time.

I would like it to somehow get cold temperatures and ice to build up in the cockpit, but it's not critical to the story. My goal is for realism, first and foremost. From what I can gather, one of the last remaining things is, what would the temperature be over the course of the atmosphere escaping in a non-linear way. It starts at approximately 22 celcius. Though I imagine the cockpit is well insulated and your character is wearing a jumpsuit so unless it's a chore to keep the ISS heated, this might be an element of story telling to abandon.

I'll update this again as soon as I can.

HAL 9000
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    There is some procedural information here that you might find useful. https://space.stackexchange.com/q/40626/6944 – Organic Marble Apr 27 '23 at 04:06
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    There are a number of useful questions about hypoxia on aviation.SE, like this one and this one that explain what happens during a gradual loss of pressure. Aside from the last few minutes when the final bit of air escapes, your scenario will play out similarly. – Cadence Apr 27 '23 at 05:32
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    you may as well watch the most horrifying case of mild hypoxia that still haunts me to this day. Spoilers: everything turns out fine, it's just a demonstration. – Erin Anne Apr 27 '23 at 06:30
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    The first medical thing to happen quite immediately is a sharp rise in their adrenaline levels if they are woken by a loud alarm sound in the middle of the night. – asdfex Apr 27 '23 at 08:11
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    Aviation.SE is full of related Q&A. Cabin pressurization is essential for a lot of airplanes. – fraxinus Apr 27 '23 at 13:56
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    https://en.wikipedia.org/wiki/Soyuz_11 The command capsule separated from the larger "work compartment" in preparation for reentry, but unknown to the crew, a small pressure-equalization valve in the hatch between the two compartments had stuck open. The valve was behind where the cosmonauts were strapped in to their seats, and by the time they realized what happened, it was too late for them to reach it. The pressure in the command module reached zero in less than three minutes after separation, and it's estimated that the last crew member lost consciousness in half that time. – Solomon Slow Apr 27 '23 at 16:07
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    Reminder: you'll need to somehow excuse how come there's no alarm or the alarm fails. Any such environments would always come with a pressure drop alarm. – Emilio M Bumachar Apr 27 '23 at 17:08
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    [From a game-dev perspective]: Maybe make the oxygen mask available as some sort of "milestone" or after a short introduction/tutorial puzzle – Hobbamok Apr 28 '23 at 07:43
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    denial, anger, bargaining, depression, and acceptance – uhoh Apr 28 '23 at 14:13
  • As Organic Marble's answer shows, the atmosphere "never" "fully escapes" because the pressure loss is inverse exponential: Because the curve flattens, a little air will remain for a long time, although increasingly little, of course. What you need to be more specific about, therefore, is how much pressure you want to have left after 30 minutes (it will never be 0). Is it 1% of the original pressure? 0.1%? This will determine the point in time when the oxygen partial pressure drops below the point where the pilot stays conscious. (Plus: What gas mix and hence pressure do you start with?) – Peter - Reinstate Monica Apr 30 '23 at 10:21

4 Answers4

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To understand subjective symptoms of a hull breach, it is important to remember that respiratory drive (the sensation of shortness of breath) is driven by blood CO2 level, not blood O2 level. As long as CO2 is being eliminated, there is very little sensation of shortness of breath.

This is why people in low O2 environments generally pass out and die without much of a fuss.

Low O2 is a real risk in “confined spaces” such as empty steel tanks. Steel oxidizes and absorbs oxygen, leaving the confined space full of nitrogen. A person entering the space continues to breath, eliminating CO2 and feeling quite OK. Their blood O2 slowly decreases. They feel the need to yawn. Then they lie down and die.

Same with carbon monoxide poisoning. The person continues to ventilate and blow off CO2, so they do not feel short of breath as their tissue O2 partial pressure falls.

Hypoxemia (low O2 in blood) can also produce anxiety and agitation. Agitation is not good in combination with loss of judgement. The effect is like a cocktail mixed with an "energy drink".

In your game scenario, characters will lose judgment, get agitated, be vaguely aware something is not right, then die.

Hopefully, there will be alarms ringing long before your characters pass out. If pressure gets low enough to muffle alarms, everyone would already be unconscious.

One of the earliest "alarms" will be pressure sensation and popping in the ears. This occurs with a pressure drop of about 15mmHg (0.02 atm)

A hole can make a very good whistle. The whistle noise is produced downstream (outside the hull). There would not be a significant audible whistle inside the spacecraft since the wavelength of the sound is generally longer than the diameter of the hole. Leak detectors used on ISS detect short wavelength ultrasound.

Dramatic physical changes such as swelling of hands and face, as well as "tongue boiling", would not occur before the onset of unconsciousness.

Woody
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    That was a question in my mind, of whether the depletion of oxygen would affect the person first and foremost. My seventh (bonus question) about having access to oxygen might make for a more dramatic scenario and give the character more time. How do you think the events might change with plentiful oxygen from a mask? I'm thinking cold temperature might play a part in the time-line, along with swelling and such, but I'm still unsure. A tank that gives you an hour of oxygen might replenish the atmosphere and just prolong the same events of gently passing out, but maybe not? – HAL 9000 Apr 27 '23 at 13:23
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    I do not have a link handy, but there are videos on youtube of pilots undergoing hypoxia tests. Basically they are put into an environment with no oxygen, and are asked to do simple tasks. The idea being that everyone feels and reacts differently under these conditions, and pilots need to learn how their own bodies will react so they can hopefully catch the symptoms while they can still do something about it. The rate of mental desegregation is very rapid, and these videos can be unsettling to watch. These might be a useful reference. – Chuu Apr 27 '23 at 15:01
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    @HAL9000 ... With regards to supplemental O2, the important quantity is the partial pressure of O2 in the inspired air. This obviously cannot be greater than the ambient pressure. Once ambient pressure drops below about 21% of atmospheric pressure, even 100% O2 will have a lower partial pressure than air at 1 atm. – Woody Apr 27 '23 at 16:17
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    @Chuu I realized I had sleep apnea, because I would wake up in the middle of the night confused. It would occur to me, eventually, that I was barely breathing, and I'd take a deep breath. Almost instantly my faculties would return to me. I guess I kinda accidentally high-altitude trained myself :) – Ryan_L Apr 27 '23 at 23:34
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    @Ryan_L good for you for figuring that out! (and for looking on the bright side) I hope you've followed up with a doctor/specialist, there's all kinds of long term deleterious permanent effects on various systems that result from regular repeated events like this. – uhoh Apr 27 '23 at 23:46
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    @Woody can you elaborate why the pressure from a respiration mask can not be greater than ambient pressure? It doesn't seem obvious to me. – Kritzefitz Apr 28 '23 at 12:04
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    @Kritzefitz ... for air to be expired, pressure in the lungs must be higher than in the upper airway. So mask pressure higher than ambient hinders expiration. Only a small pressure, such as the 0.014 atm used for treating sleep apnea, can be tolerated. Also, pressurizing the mask (and therefor the chest) would decrease venous return to the heart. Normal venous return pressure is .008atm so it takes very little increase in intrathoracic pressure to reduce venous return. This is why space suits are pressurized, not just the helmet. – Woody Apr 28 '23 at 14:03
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Supplementary answer

For your timeline, it's important to note that the pressure drop is not even remotely linear. The flow through the leak is large at first because the differential pressure is highest, then it drops off in an almost exponential curve.

Here is some real data from depressurizing a shuttle airlock from 10.2 psi to vacuum. There were 2 hole size settings on the depress valve, but this plot shows a depress using only the largest size. The "plateau" is where the crew closed the depress valve for a time per procedure.

enter image description here

I cut-n-pasted the two parts of the curve together so you could see the pressure profile of an uninterrupted leak (just the shape - ignore the x axis values that I messed up):

enter image description here

Notice how rapidly the pressure drops at first and then the curve shallows out.

Organic Marble
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6.) If noise was occurring from any source, would it become more silent as time goes on... or just stop all together at some point?

Yes it would become quieter for two reasons;

Please note that the "best" sound at least small leaks make is often slightly above our hearing in the near ultrasonic. Ultrasonic detectors are used as leak detectors on the ISS!

That means that the astronaut with the most acute high frequency hearing may hear the leak sooner or at a further distance than others.

1this speculation is an instance of uhohumor™

uhoh
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    If you had a slowly depressurizing chamber, I would think any change to the nature of sound would happen long after the pressure had dropped below the threshold for consciousness. The top of Mt Everest is right on the edge of how high as a human can survive without supplemental oxygen, and sound works just fine up there. – Darth Pseudonym Apr 27 '23 at 12:30
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    Pretty sure bell jars are named because they are bell shaped. – Martin Bonner supports Monica Apr 27 '23 at 13:35
  • @DarthPseudonym sure; I don't know what twists and turns the plot will take; maybe there's an experiment running involving the effect of sound on flames or suspension of particles in microgravity and somebody noticed they needed to increase the sound level by 1% to achieve the same results as yesterday. I'm of the school of thought that if a tree falls in a forest and there's no humans to hear it, it does indeed still make a sound, (and that the sound of one hand clapping is a very faint "swoosh" inaudible to humans). – uhoh Apr 27 '23 at 23:29
  • @MartinBonnersupportsMonica ya that speculation is uhohumor™ I've added a footnote to that effect. – uhoh Apr 27 '23 at 23:33
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There was a famous incident in 1966 when an engineer named Jim LeBlanc was testing a space suit in a vacuum chamber and it lost pressure. The pressure loss was fairly rapid but not abrupt. His experience seems to match what other answers indicate, but he did report feeling the saliva on his tongue starting to bubble just before he passed out. (I imagine this was because the pressure loss was fairly rapid so he had enough oxygen in his blood to remain conscious until the point where saliva would boil.) Here is a documentary clip on YouTube.

Mark Foskey
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