Re-certification is required on portable propane cylinders (DOT requirement) 12 yrs. after mfg. date (Stamped on safety collar)
Visual Inspection......good for 5 yrs. ANY bulk propane dealer can do inspection and issue new certification decal. (Can be redone ever 5 yrs.) Cost can be $5 to $35 depending on who/where done. No standard fee.
2 other methods used re-certs good for 7 or 12 yrs. Both require actual testing of cylinders
5 yr Visual is most common method
LINKAlternative.... (IF cylinder is standard 20# Vertical Style ----not horizontal ones)
Propane exchange (Blue Rhino etc.)
They re-cert cylinders that are swapped (part of business expenses)