Ron,
What pressure to use depends on the material and size you have. Whatever the value, it is far safer to test hoses using fluid pressure
rather than compressed gases.  If something lets go or fails, it takes
very little fluid expansion to relieve all the pressure in the system. A gas on the other hand will have a lot more energy to release.  Several
year ago there was an article in the LNN that described a great homemade
hose tester made from plumbing supply parts.  At the center is a cross. One leg attaches to the hose being tested, one leg to a pressure gauge,
one leg to a zerk fitting, and the leg opposite the hose is attached to
a shut off valve and a garden hose fitting.  The pressure test is
conducted by filling the subject hose with water and capping off the
open end, shutting off the water supply and then pressurizing the system
with a grease gun.  -works very well.  I used it on all fuel and oil
lines.
Chris Zavatson
N91CZ
360std