Do dogs constantly sniff?

Hi all, my dog was just laying on me and I had my ear to his throat and i couldn’t hear his breathing. It was never a long in hale but multiple in-one inhale and a solid exhale. Surely now that he’s off and resting it looks like regular inhales. I’m not worried about this and this isn’t a medical question but just got me thing. Are they constantly sniffing when awake? He seemed pretty calm when he was laying on me so not excited cuz then he’ll probably smell more often.