<blockquote><font size=1>In reply to:</font><hr>
I don't know about the laws in Mass., but I do know you'll need to check the stamped dates on the bottles. If the bottles are past the dates the bottles will need to be hydro tested. Your welding supply will be able to get this done.
<hr></blockquote>
In WA state, when you get your bottles 'filled', you actually turn in your used/empty bottles and they give you a different pair of bottles that you keep indefinitely. Chances of seeing your original bottles again are really really low! There is a large rotating stock of gas bottles in the state. You don't actually own your specific gas bottles, you merely own the rights to two of the rotating stock. As such, the tank testing is done by your gas supplier and they determine if the bottles are suitable for continued use.
I thought it worked like this all over the country, but perhaps someone can enlighten me?
Kevin