One of their reference links (https://www.dhs.gov/news/2017/05/25/written-testimony-cbp-se...) does mention that they are piloting a study to see if dogs can detect fetanyl, but I'm guessing it's either not going great, or they just want to explore some other options.

Hopefully this doesn't mean they just killed a lot of dogs from inhaled Fentanyl.

Thanks for the link - I greatly appreciate the help!

Aside from signal om demand training issues airtight sealing defeats them - let alone ones which don't have a discernible scent.

This is a crucial point. Vendors these days (at least the good ones) properly package their goods with vapor barrier vacuum-sealed bags. Even better, some use Mylar bags which provide a nice metallic aluminum barrier.

You could hold a Mylar bag of weed up to a well-trained drug dog, and it would not trigger. (Unless commanded to falsely by the officer, of course :)