Suppose we have a sealed room, the room is a cube, half the room is filled with dry ice. What will happen when the dry ice sublimates to CO2, will the pressure of the room increase dangerously as the temperature increases to room temperature?

PS: Don't worry about me, I have an oxygen tank and am protected from the cold.

Will I die from the pressure increase?


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  • 3
    $\begingroup$ You'll need some kind of sealed suit to avoid carbon dioxide poisoning. BTW, the $\mathrm{CO_2}$ will melt to a liquid, once the pressure gets high enough. $\endgroup$ – PM 2Ring May 13 at 14:02
  • $\begingroup$ @PM2Ring I have an oxygen tank and what is "$\mathrm{CO_2}$", I am new to this. And are you saying that the dry ice will sublimate and as the pressure and temperature increases it will become liquid CO2? $\endgroup$ – Sykhow May 13 at 14:09
  • $\begingroup$ CO2 is carbon dioxide. Dry ice sublimates at normal air pressure, but above 5.1 atmospheres of pressure it can melt into a liquid. Just having an oxygen tank isn't enough. You need a mask or suit that will stop the CO2 from getting into you. When the pressure is high enough, without a suit, the CO2 may kill you just by passing through your skin. $\endgroup$ – PM 2Ring May 13 at 14:18
  • $\begingroup$ Do gases pass through skin at high pressures? $\endgroup$ – Sykhow May 13 at 14:30
  • 2
    $\begingroup$ Yes, but it's usually not a fast process. But CO2 is very water-soluble, so that will make it easier for the CO2 to get in. I have no idea of the relevant numbers for that, but the pressure in your scenario could get quite high. $\endgroup$ – PM 2Ring May 13 at 14:33

Depends mostly on temperature. For simplicty let's assume the room has a volume of $20m^3$ so we have $10m^3$ of dry ice at, say -80°C, and $10m^3$ of air at 25°C. That's about 16000 kg of dry ice and 12kg of air. Once you connect the two, the air will simply cool down rapidly to -80°C. Given the massive difference in mass the final temperature will be very close to -80°C and there will only be a very slight rise in pressure. If you are temperature protected you will be fine.

Now if you apply external heat (or have poorly insulated walls), the temperature will start to rise. As the ice goes above -78°C the dry ices will start to sublimate and the pressure will rise. That also increases the sublimation point. When you hit about -56°C ther pressure will be 500kPa pressure. At this point liquid $CO_2$ becomes possible and the ice will start to melt. 500 kPa is the same pressure you would experience at a water depth of 40m, so with proper gear and training this is entirely survivable.

If you finally reach room temperature, the liquid $CO_2$ will boil and you'll end up just shy of the region where $CO_2$ becomes Supercritical carbon dioxide. Final pressure will around 7MPa and you'll have a mixture of liquid and gaseous $CO_2$, with the majority still being liquid. That pressure correponds to a water depth 700m which is just about at the hairy edge of what humans can do provided enough training, gear and process and only for very short time periods.


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