Exactly what it says on the tin. Kleeber the warrior is wearing a gambeson and carrying the standard adventurer's gear (leather backpack, 100ft of hemp rope, bedroll, spare clothes, waterskin, dry rations, and the 10 foot pole, some metal knicknacks like a spork, a knife, etc) and some weapons (longsword, dagger, shortbow, arrows).

Kleeber triggers a trapdoor in the Dungeon and falls into a 20 foot cube room that seals itself. The atmosphere in the room is pure oxygen and there's no light coming in. He uses a magical torch that doesn't need ignition, just a command word. That was a single-use enchantment and nothing else on him is magical. There is a pump sending more and more pure oxygen into the room. The walls and the pump are indestructible. The pump can't cause too much of a pressure shift in five minutes.

Physics and chemistry are the same as Earth. The torch is just a oil-soaked rag around a stick. Please note that the adventurer setup is just for ambiance. You could just as well put a redshirt cadet in a forcefield chamber with the same objects and the question remains the same so long the atmosphere remains pure O2.

Assuming that nothing else caused sparks before the torch is lit up, what happens in the first five minutes?

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Commented Sep 12, 2019 at 12:05
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    $\begingroup$ Sidequestion: How does he carry all that stuff?! $\endgroup$
    – Erik
    Commented Sep 12, 2019 at 13:45

7 Answers 7


Apollo Fire and Wick Effect

I generally agree with Halfthawed, but I had some additional thoughts on the matter. There is one well known and documented incident with fire and people in a pure oxygen atmosphere: the 1968 Apollo 1 accident.

The fanatic overexaggerated fear of a pure oxygen atmosphere is rooted in the horrible 1968 Apollo 1 accident where while ground testing a fire broke in the pure Oxygen environment of the capsule burning the three astronauts alive. It is a common misconception that NASA switch to Nitrogen-Oxygen mix as a result of the accident, in fact, the Apollo Program continued to use pure Oxygen air till the last mission, Apollo 17 and use the mix on the ground, switching to pure oxygen on the rocket ascend to orbit. Another misconception is that the Apollo 1 inferno is solely the fault of the pure oxygen atmosphere, the reason the fire break out and burned the astronauts alive is caused by the ground testing conditions. The lunar command module was over-pressurized to 1.2Atm in order to check the module tolerance to 0.2Atm pressure gauge it will endure in space. The combination of 1.2Atm of pure oxygen and the full gravity of Earth that induce convection currents feed the flames with oxygen and remove the carbon dioxide created the perfect storm that consumes the module and the astronauts. A low-pressure pure Oxygen is still dangerously flammable though, the air contains as much Oxygen molecules as Earth atmosphere but without the damping effect of the inert Nitrogen, any flame ignited have the potential to evolve to a major fire. - Atomic Rockets Sidearms

Another thing that made the Apollo Fire so bad was that the astronauts and the equipment were "soaked" in oxygen. The higher than normal ambient partial pressure of the oxygen (1 atm compared to 0.21 atm) makes the oxygen diffuse into the human body and your adventurer's equipment. This creates a very bad fuel + oxygen mixture.

Now let us consider the odd cases of spontaneous human combustion and the related wick effect. Normally this wouldn´t be an issue for a living human as the fire starts really slow and incinerates the body over hours (see video, warning pig carcass), but since your adventurer is soaked in oxygen and might be clumsy/unlucky with the brightly burning torch, the fire might overwhelm him and will continue to burn him until only ashes remain. The fact that more oxygen is pumped into the room makes the fire event more likely. He might die a horrible death.

However, I think it is more likely that oxygen-poisoning will get him as the partial pressure of O2 in the room increases. He'll most likely throw away the torch in shock as it gets hotter and brighter. Again, if he isn't careful a spark might hit him and he'll have to fight his burning equipment as he gets soaked in more and more oxygen. This path too will lead to a corpse looking like that of a spontaneous human combustion victim. I'd include a picture, but these are somewhat gruesome so just google them yourself.

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    $\begingroup$ Thank you for not including the photo $\endgroup$ Commented Sep 10, 2019 at 2:39
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    $\begingroup$ @LorenPechtel However, fire requires fuel. If the adventurer has thrown the torch away in shock, and the floor (being indestructible) cannot burn, then the fire has nothing to spread along $\endgroup$ Commented Sep 10, 2019 at 8:16
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    $\begingroup$ @OrangeDog Yes, the adventurer is initially in a 1 atm O2 atmosphere. However the I assumed that the pressure would increase and 1.2 atm isn't so far of 1 atm. I would have preferred data for 1 atm, however noone I know of ran experiments on how well living humans incenerate in a pure oxygen atmosphere at incremental pressure rises of 0.2 atm. ;) $\endgroup$ Commented Sep 10, 2019 at 11:52
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    $\begingroup$ "... but since your adventurer is soaked in oxygen ..." - Are you sure? From the question, I assume the adventurer lights the torch shortly after arriving in the room, and I imagine it takes significant time for oxygen to diffuse into his body. (If that even really happens, none of your sources confirm this) $\endgroup$
    – marcelm
    Commented Sep 10, 2019 at 15:40
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    $\begingroup$ "he'll have to fight his burning equipment" -- that could be a losing battle. $\endgroup$
    – Yakk
    Commented Sep 10, 2019 at 15:55

The torch burns quicker. A lot quicker, but you won't get a violent explosion. Fire requires three things - heat, fuel, and oxygen. You've increased the oxygen, but you haven't increase the fuel, so all will happen is that the torch will burn out far faster - if it lasts for 10 minutes, it might not even last for one. The oxygen won't ignite itself. Something like 2:1 hydrogen gas to oxygen, on the other side, would be far deadlier, but that's not what's in the room.

That's what happens to the torch. The adventurer gets oxygen poisoning because the 100% oxygen gas is not at low pressure and will probably die from a seizure if he stays in the room. EDIT: To clarify, the oxygen poisoning will occur within five minutes of breathing 100% oxygen at 1.0 amu for five minutes, death will only occur if you stay in the room for longer. The oxygen poisoning will wear off by breathing normal air.

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    $\begingroup$ +10 for the part about oxygen poisoning $\endgroup$ Commented Sep 9, 2019 at 17:46
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    $\begingroup$ He probably won't die. Seizures are listed for 4 times atmospheric pressure, it's unlikely to be that high in the chamber. $\endgroup$ Commented Sep 9, 2019 at 17:47
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    $\begingroup$ He won't suffer from O2 poisoning in five minutes. science.howstuffworks.com/question4931.htm $\endgroup$ Commented Sep 9, 2019 at 17:50
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    $\begingroup$ L. Dutch read carefully: "In contrast, when 100 percent oxygen is breathed under high pressure (more than four times that of atmospheric pressure) [...] seizures" So you need to pump a lot of extra oxygen in there $\endgroup$ Commented Sep 9, 2019 at 18:12
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    $\begingroup$ You need about 1.6 bar pp02 (eg. regular air at 8 bar) to get CNS effects from oxygen toxicity in a reasonable timeframe. At 1 bar ppo2 or below (eg. this situation) you'll get few interesting physiological effects for a few hours, and Keebler will probably be dead from chronic pulmonary O2 toxicity (in about 48 hours) before any CNS effects occur. I'm not seeing any references to O2-induced seizures at normal atmospheric pressure, but if anyone else has some I'd be interested. $\endgroup$ Commented Sep 9, 2019 at 18:54

Regarding Oxygen toxicity

This is rather an extended comment with some calculations than an actual answer.

I'd like to back up the matter with some actual calculations. I presume you mean a $20ft \times 20ft \times 20ft$ room when you say "20ft cube room".

That means we have a volume of $V=226.5m^3$. Let our initial pressure be at $p=p_0\approx 100kPa$. Let $j$ be the volume flow per second of oxygen entering the chamber. From the ideal gas law we can then estimate how fast we will reach a critical level of oxygen pressure, as was linked in other answers and is more than 4 times atmospheric pressure.


where $n(t)=\frac{j\cdot\rho}{M}\cdot t$

with $\rho=1.429 kg/m^3$, $M=0.032kg/mol$ and of course $t=5min=300s$ and $p(300s)=4p_0$. We can now plug everything in.

We can calculate $n_0=\frac{p_0V}{RT}=\frac{100kPa226.5m^3}{8.314J/(K mol)293K}=9298mol$

$j=\frac{4Mn_0}{\rho t}=\frac{4\cdot 0.032kg/mol \cdot 9298mol}{1.429kg/m^3\cdot 300s} = 2.78m^3/s$

So our pump will need to put at least 2780 litres of oxygen per second in the room at a constant rate in order to reach a potentially deadly level of oxygen just by the end of the 5 minutes.

  • $\begingroup$ Uh... something seems wrong about the conclusion of this. Pumping in "litres" of a gas is not descriptive. Litre is a volume, not mass - a "litre of gas" could differ wildly depending on the pressure the gas in that litre is under. $\endgroup$
    – Kevin
    Commented Sep 10, 2019 at 17:57
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    $\begingroup$ @Kevin Pumps usually have almost constant output volume per second for such low pressures 0.1-0.4 MPa. Think piston action - piston doesn't care much about the mass of gas. $\endgroup$
    – kubanczyk
    Commented Sep 10, 2019 at 18:50
  • $\begingroup$ @kubanczyk Yeah, but the question is how much oxygen would have to be pumped into the room to get O2 toxicity in 5 minutes. Aka, where the oxygen pressure gets to a certain point - which is just mass/volume. Volume is static, so the measurement should be the amount of mass needed to get to toxicity. So I'm not understanding how an answer would be expressed as a volume, since the amount of oxygen entering the room in that volume isn't defined. (Aka, imagine pumping in 2.8 kiloliters/sec of extremely low pressure oxygen.) $\endgroup$
    – Kevin
    Commented Sep 10, 2019 at 19:27
  • $\begingroup$ Within this answer, it's the pressure function over time p(t) that determines the volume-per-second output. Since that pressure function is linearly increasing until it reaches 4p, the author assumed implicitly that the pump is always exactly matching the room's pressure as it increases. I get your point - it's too implicit. $\endgroup$
    – kubanczyk
    Commented Sep 10, 2019 at 21:26
  • $\begingroup$ Oh yeah, that was implied in the constant rate $\endgroup$ Commented Sep 10, 2019 at 21:52

The torch will burn much faster & hotter. There's a fairly common real-world example of this: the oxyactylene torch used for welding and cutting ferrous metals. Light it with just the actylene turned on, and you get a rather cool yellow flame that smokes a lot (rather like your adventurer's torch). Increase the flow of oxygen, and it burns with a hot, blue-white flame. https://en.wikipedia.org/wiki/Oxy-fuel_welding_and_cutting


Nothing of Note, Sorry.

Thus far almost everyone has been mesmerised by the Red Herring of oxygen toxicity. Given the time constraint of the query and given the chemistry of the experiment, I'm sorry to say that every answer, including the accepted, that involves toxicity is going to fail a reality check.


  1. Let us not forget that Kleeber the Klobberer is bringing in a N2 soaked micro environment of his own. His own clothing, his hair, his bed roll, his barbarian hat, his spare clothing, the rope --- none of that is going to be instantly saturated with pure O2 inside of the time frame of the query.
  2. Once he tumbles into the chamber, the N2 micro environment that surrounds him will create a kind of (temporary) shield. Once he realises it's dark and lights his torch, that N2 will serve as a buffer between the Rumelian candle of his torch and his own combustible gear. Surprise at the bright light and flame will most likely cause Kleeber to throw the torch across the room, thus giving him distance from the fire source as well as gaseous armour.
  3. No one has yet taken into account the products of combustion. Once Kleeber enters the chamber, thus setting off the five minute timer, the (metabolic) combustion happening within his own body is going to pump CO2 into the atmosphere. Being an uncouth warrior hero, if he lets off a couple decent farts, he's going to pump quite a bit more CO2 and N2 into the atmosphere. Once he ignites the torch, the combustion of the oil, cloth and wood is going to rapidly emit a considerable amount of CO2 and H2O into the air. Wood emits the most CO2 of any common fuel, I've read 1900g of CO2 per 1000g of wood. A standard adventurer's torch weighs in at about 3 kg or so, which will make for a rapid infusion of nearly 6 kg of CO2.
  4. Oxygen toxicity, as I've stated in other answers, is a thing. However, given the time frame of the query, it's just not of concern. It takes a while --- more than the five minutes allotted by the experiment --- to obtain relatively mild symptoms. Much more severe symptoms of course will occur as the time exposure is increased. Kleeber isn't going to be in this environment for a long enough time to suffer any serious reaction to the O2.


  • The initial conditions of the experiment, a pure O2 atmosphere, will be altered once the subject enters the chamber, bringing in outside & inert gasses such as CO2, N2 and even H2O plus traces of other atmospheric gasses.

  • Fire in an O2 rich environment will release CO2 very rapidly, changing the chemistry of the atmosphere. Perhaps not enough to prevent oxygen toxicity over a long period of exposure, but sufficiently, perhaps, to keep our hero safe for the short duration of his exposure.

  • As the wood of the torch is consumed and converted to CO2 & H2O, the subject will no longer be in a pure O2 environment. The wood will be consumed and the fire will self-extinguish. There will be little risk of clinically adverse oxygen poisoning within the given time frame.

A final consideration:

  • Depending on the flow rate of the O2 pumps, Zappo's Thaumic Adignificator, might just get blown away on that 2780 l.p.s. gas flow without ever even lighting the torch! In that case, Kleeber won't risk possible combustion at all, and while the O2 levels will generally be higher for the duration of the experiment, his imported micro environment and the five minute limit will still keep him safe from oxygen poisoning.
  • $\begingroup$ I have to agree that 02 poisoning won't happen in 5 minutes. $\endgroup$ Commented Sep 11, 2019 at 16:30
  • $\begingroup$ I'm not convinced N2 saturation will be significant. even localized oxygen saturation in a standard atmosphere will overwhelm whatever N2 saturation is present in an object, and cause it to burn much more violently. $\endgroup$ Commented Sep 12, 2019 at 17:15
  • $\begingroup$ Note that CO2 toxicity occurs at a much, much lower level than O2 toxicity. So while releasing a large amount of CO2 in a confined space might technically prevent O2 poisoning, it's not going to save the life of the hapless adventurer. If anything it'll kill him faster. $\endgroup$
    – Perkins
    Commented Sep 13, 2019 at 18:05

A violent, rather sudden death.

When you are unsuspecting, you usually do not hold a torch with the burning end as far away as possible. You hold it in a comfortable position, so it will be maybe half a meter away from your head.
It's dark and unsuspecting Kleeber wants to see, so he summons that torch, in a normal, comfortable position.

The room was filled with 100% oxygen, and a pump keeps pumping extra oxygen into the room. That was happening during the, say, 5-10 seconds (probably more like 20-30 seconds!) while Kleeber was recovering from the fall, and getting up on his knees, too. So the room is not just filled with oxygen, it is filled with pressurized oxygen (... of unknown pressure). I'm neglecting the volume that Kleeber's body displaces, we can assume some oxygen went "out" when he came "in".

The torch, which is not very far away, will thus flash very brightly. How brigthly depends on the actual pressure and is pretty tough to tell, but let's just say it's worth a torch 5 times as big. That's probably not an awful exaggeration. No, it will not explode. But it will give off a considerable amount of very, very uncomfortable heat. Note that normally there's smoke and such (and flue gas is in principle burnable, only just there's normally not enough oxygen, except... think of the famous "Backdraft" movie). We don't have that here, it all burns up, there's plenty of oxygen.
So that will mean that not only Kleeber's sleeves (the leather parts will be only superficially oxygenized, but the cloth parts will be soaked) will catch fire, but also Kleeber's hair, which is a desaster. Not only because violently burning hair which wraps your head (possibly including respiratory paths) in a fireball is a definitely no-fun condition, but also because the sparks of burning hair will set everything else on fire, too.
There are documented cases of smokers who had such a funny surprise when lighting a cigarette while wearing an oxygenator. Now, that's a joke compared to what your poor Kleeber is experiencing.

High levels of oxygen, especially under pressure, can do miraculous things. Things that will not burn at all normally all of a sudden are not as reluctant to catching fire as you're used to.

There's documented cases where firefighters took an hour or two to take out a "petty fire" which they'd normally kill in seconds, solely because there was an open oxygen tube involved.


Reframing - the problem is not the torch, the problem is the oxygen.

Oxygen Toxicity

You've got an 100% oxygen environment, into which you're introducing "more and more" oxygen.

Kleeber's main problem is going to be oxygen toxicity. Lung damage, CNS damage, retinal damage.

You will also get some fairly spectacular fire, but that shouldn't be Kleeber's main concern, even if it's the most obvious.

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    $\begingroup$ @Mindwin Note the "reduced pressure". What matters is the partial pressure of oxygen, which you can think of as the amount of oxygen in the room whether or not anything else is there. 0.2 atm of oxygen and 0.8 of nitrogen is fine; 0.2 atm of oxygen and no nitrogen is fine; 1.0 atm of oxygen is not fine. $\endgroup$
    – Cadence
    Commented Sep 9, 2019 at 17:54
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    $\begingroup$ @jdunlop not within the 5 minute frame. $\endgroup$ Commented Sep 9, 2019 at 18:06
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    $\begingroup$ it's very common in medical care to receive pure oxygen at 1 atm for prolonged periods. Decades ago, there were "oxygen tents" that allowed a patient to breathe pure O2 without having to wear a mask, and a few of them were involved in horrific fire accidents -- but oxygen toxicity in them was very rare, if not unheard of, because they never got above 1 atm. The worst thing about breathing pure O2 is that if your exhalations aren't allowed to accumulate, you may suffocate because there's no CO2 to trigger your breathing reflex. $\endgroup$
    – Zeiss Ikon
    Commented Sep 9, 2019 at 18:41
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    $\begingroup$ @ZeissIkon Pure oxygen will cause lung damage after a long enough exposure. Memory says 16 hours but I won't swear to that. The thing is, doctors use it when the body's ability to absorb the oxygen is compromised, you aren't actually getting the full amount. $\endgroup$ Commented Sep 10, 2019 at 3:05
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    $\begingroup$ @Zeiss Ikon: Akso, the oxygen tents & masks for long-term use, and the nasal cannula used in portable oxygen systems, generally don't deliver pure oxygen to the lungs. Instead, they enrich the ambient air. $\endgroup$
    – jamesqf
    Commented Sep 10, 2019 at 3:23

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