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Compressed Air Can

  1. Aug 16, 2012 #1
    For starters, I have no idea where to post this question but I think this is a good place.

    Earlier today I bought a compressed can of moisture-less duster to clean my computer fans with. That is all good, but when I was done I wasn't sure where to dispose of the can.

    Normally it would be safe to throw in the garbage (its non-toxic in gaseous form) but it's a very hot day (like 90ish) and even though the can says it's safe to temperatures up to 120 I am uneasy about just leaving it in the garbage.

    Can anyone advise me here?
    Thanks
     
  2. jcsd
  3. Aug 16, 2012 #2

    Drakkith

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    It should be fine. Once empty the pressure inside is far less than it was when full.
     
  4. Aug 16, 2012 #3
    That's what I was hoping, thank you.
     
  5. Aug 16, 2012 #4

    sophiecentaur

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    Once you get no more puff out of the can then you can safely use a can opener or chisel to make a hole in the can. It is then harmless at any temperature.
     
  6. Aug 17, 2012 #5
    Speaking of compressed air cans, if you use them for a few seconds they get very cold, and thus lose their effectiveness.

    So once I got the bright idea of putting the can in boiling-hot water to heat it back up. After a few seconds though I got a bit uneasy about the whole deal, for the same reason as OP was about leaving it out on a hot day. Does anybody have any idea how hot these things could really get before catastrophically failing?
     
  7. Aug 17, 2012 #6

    sophiecentaur

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    The vapour pressure of butane is about 2Bar at room temperature (i.e. 1Bar excess) and it's a bit over 15Bar at 100C. That would be significant, I think, if there was still much propellant in the can.

    The gas in the can, once the propellant has gone, will only be following the gas laws. The pressure will only increase by around 1/300 for every degree C rise in temperature at room temperature.
     
  8. Aug 17, 2012 #7
    I think we could assume the safety factor will be around 3. If there is no liquid phase in the container, then from the ideal gas law we get it should fail at 3x300 K = 900 K. Which is meaningless, because the material of the can will lose its strength much earlier than that. Aluminium alloys, the usual material here, lose 2/3 of their room temperature yield strength at about 600 K.
     
  9. Aug 17, 2012 #8

    sophiecentaur

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    The plastic bits will go long before that temperature.
     
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