I often hear stories of folks who are told they need to get their mounted tanks re-certified.
There are 3 things you need to know.
Portable tanks such as those on a trailer or used for a grill, NEED to be re-certified (DOT rules) every so often, the time between re-certs is dependent on the age of the tank so I do not worry about it and trust the pump jockey on those.
MOUNTED ASME tanks, such as those used on motor homes... Do not need to be recertified.. UNLESS....
If the tank, or valve or inlet or outlet is in such bad condition that the pump jockey is concerned.. He may to refuse to refill it till the tank is inspected by a certified inspector... Example, if the valve leaks. If there are cracks or discoloration of the brass (One of the chemicals used in Meth production (illegal) reacts with brass and discolors (And weakens) it) or other conditions or damage to the tank are bad enough to cause concern.
But if they say "It needs to be re-certified due to age".. that only applies to removable tanks you can take to the re-fill without an RV attached.
Pump jockeys are supposed to be certified.. At least in two states (SC and MI) I once listened to a test correction and review session for said jockies in mi.
This info comes from that session.
One of the questions ask was "What happens if you get the proper mix of Propane and air and there is a spark".. I chimed in (Since it was a review session) "You land two counties over".. After the laughter died, the instructor gave me some pleasure by saying "Exactly" then giving the proper answer "An explosion".