All passengers went through a ‘puffer/sniffer’ the last time I flew out of Denver 2 yrs. ago.
No more, they were removed, IIRC because they were as effective as hope for, and required lots of maintenance.
We first saw the "puffers" in Tampa about 2 years ago. They were there for maybe three months, then they were gone. I have always wondered what happened to them, why, and how much we paid for each of those now-unused machines. We have flown out of Denver several times in the last three years and I don't remember ever seeing them.
What I want to know is "WHAT'S WRONG WITH USING DOGS?" Good Grief! That should be a no brainer!