Originally Posted by Pick
You should have told the U-Haul attendent that it was a new tank, and they would have purged it, for a small fee. Purging takes about 1 to 2 hours, to do it right. It involves filling the tank with a small amount of propane then bleeding it out and refilling about five times. Some tanks come purged with nitrogen from the factory, so they do not need propane purging.
I don't believe this is accurate, at least not in California, and laws pertaining to propane tanks may
well be Federal in nature (I would suspect so (DOT)).
It is my understanding that prior to about 10 years ago, propane tanks were factory-filled with an inert gas for pressure testing and transportation, such as nitrogen, and that had to be purged prior to filling, otherwise a portion of the "filled" tank would be compressed nitrogen (not flammable). While normal atmospshere is nearly 80% nitrogen already, the pure nitrogen-fill would eliminate the other 20% (actually 22%), including oxygen. In other words, a 100% nitrogen-filled tank would have to be purged in order to a full tank of propane.
Today, and for the past several years, propane tanks are factory-tested under vacuum, i.e., they have negative atmospheres at the factory for testing purposes, and are transported that way. These tanks do NOT need to be purged, unless the tank valve has been opened and the tank has been allowed to fill with atmosphere.