The question has implicitely a lot of variables attached to it:

  • volume of the room
  • activity
  • how closed the room is
  • size of the person (I'm 168cm long and 64 kg heavy)

That could probably be turned into some formula and I am interested in scientific insights.

But at the end of the day my question is actually of very practical nature. I have a small room - about 1m x 2m x 2.5m = 5m3 - and I would like to use it as super-quiet place for meditation, reading etc. - hence calm activities, no excessive moving around. To improve sound proofness I'll probably also increase the sealing of the door and there is no ventilation - no air exchange.

Now if I close the door - how long can I expect to stay there without the air quality deteriorating to a level where my mental processes start to be impaired by it?


Since you are considering to meditate in the room, without any excess of activity, you can consider the average resting O2 consumption, which is C = 3.5 mL/(min.kg) [1].

If we ignore the volume of your body, initially the room is filled with VO2(t0) = 0.21 * 5 = 1.05 m3 of O2.

With you breathing in the room, you can consider the volume of O2 in the room as a function of the time: VO2(t) = VO2(t0) - C * M * t where M is your weight in kg, and where C is converted to m3/(min.kg).

An oxygen defficient atmosphere is an atmosphere for which oxigen content is below 19.5 % of the volume [2]. An oxygen defficient atmosphere can be dangerous for your health. So in your case you need to find the value of t for which VO2(t) becomes inferior to the threshold Th = 0.195 * 5 = 0.975 m3.

So the maximum time you can spend in your room would be: tmax = (VO2(t0) - Th)/(C * M) = 335 min = 5 h 36 min

Of course, this value is a bit surestimated, and you should leave the room before that time.

[1] M. Kwan, J. Woo & T. Kwok (2004) The standard oxygen consumption value equivalent to one metabolic equivalent (3.5 ml/min/kg) is not appropriate for elderly people, International Journal of Food Sciences and Nutrition, 55:3, 179-182, DOI:10.1080/09637480410001725201

[2] https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=12716

  • 2
    $\begingroup$ There is another problem: The rising concentration of CO2. If the volume of it get over 10 Volume% in the air, this is dangerous. $\endgroup$
    – Chris
    Nov 4 '16 at 13:40
  • $\begingroup$ @Chris During respiration 1 mol of CO2 is produced for 1 mol of O2 consumed. Both gas being at the same pressure, we can consider that C is also the average CO2 production. $\endgroup$
    – Flo
    Nov 4 '16 at 13:53
  • $\begingroup$ Not because the volume is getting bigger - CO2 in large concentrations is a problem for breathing. $\endgroup$
    – Chris
    Nov 4 '16 at 13:57
  • $\begingroup$ @Chris Sorry I involuntarly send the comment above before it was finished. So, CO2 production is also a function of the time: VCO2(t) = C * M * t (initial amount of CO2 can be ignored). So VCO2 gets above 10% of the volume for t'max = Th(CO2)/(C*M) = 37h12min. t'max being superior than tmax, the first limitation is O2 depletion. $\endgroup$
    – Flo
    Nov 4 '16 at 13:57
  • $\begingroup$ @Flo Can you check your citations for dangerous CO2 and O2 concentrations? 19.5% might be OSHA's suggestion for a safe environment, but the more severe effects of O2 require much lower concentrations; CO2 on the other hand can cause mental confusion well before 10%. That said, the estimation in the original answer is still reasonable and should provide a decent safety margin given the assumptions made. $\endgroup$
    – Bryan Krause
    Nov 4 '16 at 16:35

The average untrained healthy male will have a VO2 max of approximately 35–40 mL/(kg·min). [1]

So even if we take minimum value, your consumption in a minute is 35x64 = 2.24Liters. But NOT all O2 is consumed since about 16% is exhaled along with 5% CO2.

So, Oxygen will get 50% by around 4 hours and I highly doubt if even 50% Oxygen is enough to breathe properly, you will feel suffocation much earlier. [2]

[1] Guyton, A.; Hall, J.E. (2011). "Textbook of Medical Physiology, 12th Ed.". pp. 1035–1036. [2] https://www.princeton.edu/%7Eoa/safety/altitude.html


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