Re: How does helium get into the tank used to fill balloons?

One part of the answer is that a compressor is used to pump up the 
pressure on the gas and shove it into the tank.

But the more interesting aspect is where the purified helium gas comes 
from in the first place.

Helium is produced by extracting it from natural gas, in which it is a 
small impurity (typically less than 1%).  This is usually done 
cryogenically (in other words, you get the gas very cold so that the other 
components liquefy, leaving the helium gas behind [sometimes the helium 
itself is then liquefied]), but other separation methods are occasionally 
used.  Most of this is done in the Texas panhandle, because the gas there 
is richer in helium than it is most other places.  There is even a helium 
monument in Amarillo:
http://www.amarillo-cvb.org/helium.html

Helium is actually a precious natural resource.  Once it is used, it 
typically escapes into the atmosphere (and eventually into space), and 
there is no easy way to "make" more.  So the U.S. government has a program 
to manage helium production and make sure there is enough for defense, 
space, and research needs.  More information can be found at:
http://www.nm.blm.gov/www/amfo/amfo_home.html

Allan H. Harvey, aharvey@boulder.nist.gov
"Don't blame the government for what I say, or vice-versa."