Compressed air Vs. Compressed CO2

[Jerrymac]

Does anyone know what the difference is? Some family members got Paint ball guns for Christmas. They came with CO2 tanks. We were wondering why everything we have looked up and everything some people have said is we can not place compressed air into a CO2 tank. AND..... we would need an air compressor used for Scuba Diving tanks. Not this little air compressor I have. But no one gives the reasons. I figured it must be something about how the different gases compress. I just figures a 100 pounds pressure of compressed air was the same as 100 pounds pressure CO2.

Any thoughts?

[Brian D. Bray]

psi is psi the difference is in the properties the gasses exhibit when under pressure.

[Jerrymac]

OK Can you explain that to me?

[Mici]

first of all, compressed air goes bad. i think that after 3 months it can not be used for breathing purposes of course.
about the compression difference, hmmm air is what 74% nitrogen, some 20 % oxy around 1%CO2 and other gases. i'd say that CO2 is much easyly compressed so you get (this is a blind shot) 10 pounds of CO2 into a gallon tank whereas you would only get 5 pound of gas mixture (air) into the gallon vessel. also, probably much less energy needed to compress the CO2.

ummm, practicly everything i wrote is from my head, figuring out why it is so, so it's probably very false, hehe.


hmm hm hm, just thought of something else, if you have 74% nitrogen, it's basicly the majority, right? so different gas has different freezeing point. blah blah, i can't explain i mean, it would take too long, but to achieve the same capacity, the nitrogen would probably only freeze your gun.
again...not sure, basicly what i want to say is, you could never achieve the same capacity.

my advice? buy airsoft guns.

[Understudy]

You exact question is on Paint Ball Nation.

It would appear the answer is compressed air.

Sincerely,
Brendhan

[Jerrymac]

That still didn't really explain why I can not/should not use my own compressor. Nor why I can not/should not put compressed air into a CO2 tank.

The only thing I saw was someone mentioning that the CO2 would be liquid in your tank after they were filled. I thought it took massive amounts of pressure to liquefy CO2. 

[Hayesbo]

alrighty, let's see if I can word this. Compressed air is just air that is compressed (squished into a smaller space) Your normal air compressor can only compress air up to about 250-300PSI. A scuba tank compressor runs at 3000PSI.

CO2 has a very beneficial property in this case. When compressed to about 800 PSI (not exact, I know, but the theory stays valid) the gas goes into liquid state. The reason that CO2 tanks are filled by weight is to measure the amount of liquid.  In a closed pressurized container, The CO2 will "evaporate" until the CO2 air pressure reaches the "800 or whatever"PSI, then the liquid will stop evaporating. The Gas will always stay at "800 or whatever"PSI no matter how much or little liquid is in the tank. Every time you pull the trigger on the paint ball gun the air/gas pressure drops a little and the CO2 liquid evaporates to compensate and bring the pressure back to "800 or whatever". This constant pressure allows for the discharge to be regulated. If you filled the tank with compressed air, once you went past the pressure that the gun was regulated to, the paintballs would drop in velocity until the speed of drool and then nothing. The same thing eventually happens with CO2 but not until all the liquid is evaporated and the remaining gas is exhausted. Since the liquid gas keeps the tank pressure constant, the liquid gas is like continuously refilling your tank. (until the liquid is gone of course)

I used to play a little paint ball, but mostly we used CO2 in laparoscopic surgery. Any trace gas that was left behind after the surgery was absorbed by the body and expelled through breathing just like the normal byproduct of breathing.

By the way, Some paintball guns are set up to use nitrogen, but they use it under the Scuba tank type pressure, not liquid. I can't explain the properties with nitrogen as my experience in that area was limited to cooling lasers. The people who used nitrogen paintball guns claimed they would shoot straighter and longer at the same velocity. In my experience, they fell to the storm of my paintball fury like everyone else!!!!   MUHAHAHAHA

Hope this wasn't too boring,  Steve

[Jerrymac]

Thanks Hayesbo. That makes everything so clear now.