bootstrap compressor ??? what is it ???

[radrush]

Ingersoll Rand bootstrap compressor with tank. What is this used for?

http://charlotte.craigslist.org/tls/5142141206.html

 

[logical]

I think it takes commonly available compressed air at lets say 120 psi and uses it as power to run a pump that creates higher air pressure in the tank.

It doesn't run by itself. Sort of a supercharger. Not real efficient unless the high pressure is only needed for short periods.