Liquid Nitrogen is used in creating atmospheric effects as well as other commercial uses--but a lot of
safety considerations have to be thought about before using it as it will remove the oxygen and create an asphyxia situation much faster than a CO2 Fogger or dry ice will. It is NOT for the Novice and should only be used by professionals and experienced handlers.
Where you can buy it is not a problem as most air/gas, welding gas suppliers and some medical gas suppliers carry it, however the AMOUNT you want to buy may be of consideration. It is very expensive first off..not really affordable for most folks for playing around with..and you must usually have your own containment for it--which is a very costly for large quantities. This alone makes LN2 effects out of the price range of most folks except large scale professionals. It is sold in dewars in some places, but not in tiny quantities where you can go pick it up off a shelf or something. Its also not something you can buy and leave sitting around for a week or two unless you have proper storage facilities--and those facilities require special construction and materials. Usually its sold in large quantities only and sold only to professionals who know how to handle it and can provide answers to what they plan on doing with it to the gas suppliers.
LN2 is not for the novice--it is very dangerous in handling even moreso than Dry Ice. It is usually sold in LARGE bulk quantities and you must have proper storage containers and facilties for it. This is not something you can pour into a theromos or a cooler and tote around... LN2 is around -375 degrees F, it will freeze and brittle plastics, foams, rubber and some thin steel and anything else it comes in contact with. It cannot be 'contained'--like capped in a
bottle for transport or in a small test tube in any form--as it will violently explode moreso then dry ice will if contained. It cannot be handled safely without a lot of precautions--it "boils" when exposed to air and can often splash and spray everything around it, and can be very very dangerous. It will freeze and destroy skin on mass contact and can cause severe burns and blindness. So proper
face shields, long sleeves, aprons and gloves are needed when handling it.
No licensing is needed in most places I have been and had it used, but I guess that will vary from state to state--and any laws on obtaining it probably will change when some redneck IDIOT decides they wanna make instant ice cream in their trailer and they accidentally
drop it on their kids.. For the average person--LN2 is not a feasable toy or thing to
play around with that is cost effective. For example, storage tanks in theme parks for LN2 effects can cost in the tens to hundred of thousands of dollars depending on its size, for its specialized design and materials. A lot of precaution, and a lot of special handling, and a lot of basic human
safety considerations IS required for dealing with LN2..
my two cents...
-w