Mustmaker wrote:
... propane tank ...
Even after multiple flushings with air, there is still a smell of the odorant.

To get rid of the smell (reprint of earlier post):
I have tried various things to get rid of the odor from propane tanks
that I've reused. I have just tried the only one that really worked:
chlorine bleach (e.g., Clorox).

I have a 10 gal tank that I wanted to use as a portable air supply. I
poured in about a cup of bleach, sloshed it around, let it sit, sloshed
a few more times. After about 24 hr., I drained the bleach, rinsed with
a little water and filled with air. The air was totally odor free.
Well, it smelled a little, more like paint thinner than anything.

Note - I did this with the valve on, it would be easier with it off, but
probably not worth the effort.

Bob