CO2 safety

  1. I was at work today, and this guy named harold who is pretty smart was discussing the safety of CO2 with his coworker. We fill CO2 tanks like those used for grilling (I think)..anyway, he said that unlike compressed air, you cannot get hurt by CO2 rushing out of a broken valve. He said that while air, if compressed enough, can lacerate/cut off a finger.

    However, he said that CO2 will not do that, no matter how compressed. One key word I heard was vapor pressure. Can someone explain this a little further?
     
  2. jcsd
  3. mathman

    mathman 6,621
    Science Advisor
    Gold Member

    It depends simply under how much pressure the gas is under while in the tank. It does not depend on the chemical composition. I presume then that the CO2 tank is under lower pressure than compressed air.
     
  4. Danger

    Danger 9,878
    Gold Member

    Are you fairly sure of that? Most barbecues are designed to run on something a little more flammable, like propane. :confused:

    Seriously, though. CO2 can give you a very nasty burn (actually frost-bite) when it leaks. It tends to form dry ice at the exit point.
     
  5. Well, I don't know what it's for actually, I was guessing at that. I suspected precisely what mathman said.

    However, can someone else give me more information on why CO2 can hurt you, or cannot hurt you?
     
    Last edited: May 29, 2005
  6. pervect

    pervect 8,041
    Staff Emeritus
    Science Advisor

    You might find the phase diagram of CO2 at

    http://www.acpco2.com/index.php?lg=en&pg=2121

    helpful. You can see that CO2 will liquefy at under 100 atm. This doesn't necessarily make it perfectly safe, but the specific concern you raised (pressure) will be limited to a fairly low value as your friend said. This safety isn't absolute either - after you raise the CO2 above 40C, you can see from the phase diagram that you are above the "critical point". Thus if you heated up a CO2 canister with a propane torch, you could probably eventually make it burst and injure yourself.

    Also note that breathing CO2 in too large a concentration is not healthy - it upsets the acid-base balance in your body. People in an enclosed area will suffocate because of CO2 poisoning before they die of lack of oxygen, for instance. It takes fairly large quantities of CO2 to be toxic in this manner, but it can be done.

    Try the MSDS for CO2, such as that at

    http://www.chem.tamu.edu/class/majors/msdsfiles/msdsco2.htm

    for more info.

    CO2 in the concentration it is found in the atmosphere isn't a problem - your body is adapted to it. Part of the purpose of anaerobic conditioning (aka wind sprints) is to increase your bodies tolerance to CO2, which is generated by normal metabolic processes, by improving the capacity of your bodie's
    acid/base buffering system.
     
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