why do compressed air cans have this in them

[ShawnD1]

if you look at your can of compressed air which i'm assuming at least one of you has, you'll see it says "1,1,1,2 tetrafluoroethane" is what's in them. um correct me if i'm wrong but isn't tetrafluoroethane flamible and poisonous? almost all halocarbons are poisonous and many halocarbons are flamible.

why don't they just have compressed normal air?

[mireland]

to keep the air fresh??? LOL. Seriously I have never noticed that before and I don't know why.

[jmichna]

1,1,1,2-tetrafluoroethane and difluoroethane are two common "compressed air" products. Neither is flammable nor toxic. They are simple asphyxiants (since they displace the oxygen you should be breathing, in a closed space you could become oxygen-deprived). Both solvents are considered "ozone-friendly," that is they do not deplete ozone like the older chlorofluorocarbons.

I'm pretty sure there are probably true, straight compressed air products, but these would have their own set of problems. An aerosol dispenser of compressed air would probably be at a much higher internal pressure in order to contain a reasonable amount of "product." The two fluoroethanes mentioned above are liquid under relatively modest pressure, and only become gaseous as you depress the spray tip and allow product to escape. You can even get some of the liquid solvent to spray out if you invert the can and press the spray tip.

Another issue with straight compressed air is it would tend to be a bit corrosive unless all the moisture were removed when the aerosol can got filled. Compressed air usually gets a bit of oil contamination (picked up from compressor components) and would need to be carefully filtered, or it would just grease up whatever you tried to dust off.

This is probably WAYYY more than you cared to know about "air dusters" but I went on a roll....


PS: re "...halocarbons are flamible...." actually halogenated hydrocarbons are used in many fire suppression systems ("Halon" is one brand name).

[Billforce]

Liquified gases (inert) typically volitalize at about 370 to1 in volume, i.e. one cu.in. of liquid becomes 370 cu.in. of gas. The reason for their utilization as a gas is their density of the product. If you merely compressed air in the same cylinder it would contain only a few cu. ft. of air, like a few puffs then nada. A large oxygen cylinder containing compressed air at even 3,000 psi would have less gas than a small canister of liquid....I don't think you would like to lug an oxygen bottle around to blow the dust out of your PC!

[ShawnD1]

actually i would... the more stuff there is, the more cold i can make things. i really like having the power to freeze things instantly.

what i really wanna see is shooting an air can with a .22 to see it freeze the surroundings and take off like a rocket

[Billforce]

Originally posted by ShawnD1
actually i would... the more stuff there is, the more cold i can make things. i really like having the power to freeze things instantly.

what i really wanna see is shooting an air can with a .22 to see it freeze the surroundings and take off like a rocket

Then get a container of liquid nitrogen like dermatologists use, it releases at -270 deg F.

[fishybawb]

-321

[ShawnD1]

what's that in SI units?

[fishybawb]

77 Kelvin