Not all propane tanks are safe to refill and need to be disposed of properly.
https://www.cnet.com/news/how-to-properly-dispose-of-propane-tanks/?utm_source=dlvr.it&utm_medium=blogger#ftag=CAD590a51e
https://www.cnet.com/news/how-to-properly-dispose-of-propane-tanks/?utm_source=dlvr.it&utm_medium=blogger#ftag=CAD590a51e