If there is no train air (e.g. from a parked locomotive or the yard air line) you can still perform a Single Car Test on a car using air from your shop compressor. This adapter is fabricated by welding a 3/4" steel nipple into a scrapped air line knuckle and then using a couple of pipe reducers to get down to a 1/4" FNPT thread, whereupon a shop air hose quick connector can be threaded into it.
Your shop's compressor will take a long time to pump up the two 100
gallon reservoirs that are typically found on a passenger car but,
after that, you should be good to go. For freight single car tests,
set the air at 90 p.s.i. and for passenger car tests, set it at 110.
Photo by E. Wilde,