Do dogs have to actively sniff to smell?

No more than you do. Their nose being wet has nothing to do with their sense of smell.

No, they smell pretty bad when they’re wet or get sprayed by a skunk. <sorry, it’s late, I’m tired, and I just couldn’t resist> ;)

I’m no professional but dogs seem to actively smell. Let me send this to another jelly.

Actively sniffing magnifies the already passively detected scent. The wet nose just captures more of the esters floating about in the air.

@canidmajor Someday it would be fun for you to do a Q about dogs (like the doc does with Covid), I’m sure many of us would like to pick your brain. :)

Aw, thanks, maybe someday!

The dog we had during my childhood on the farm loved a chase, more than a kill. He was constantly going after something. Like us, a scent can suddenly catch our attention, but then we put some concerted effort into finding a source.
I have memories of seeing him with his nose to the ground every day jig jagging along in search of a chase. It was funny when a fresh scent would come in on a breeze. His nose would point in the air, and he would look like Fred Astaire dancing around for a sense of which direction and what distance. Finally he would check the ground, then back to smelling the breeze. When finally air matched ground, zoom! Off he’d go. He would disappear for a while. When he came back prancy and spirited you could be sure he found some critter he chased as far as he could, until they found some safe spot.
He was a border collie, so his instinct was to chase, but not to kill. He would chase anything he could startle into rapid retreat. I was his cheering section.

Very cute!