I have 4 cats and two dogs. Of these, 2 cats and one dog have potty training issues on occasion. One cat likes to pee under my computer desk. I think I've managed to train this out of him, though. One cat likes to pee on my clothes. One dog occasionally can't hold it if she's locked inside for more than 5 hours. She always has a clean puppy pad to use - well away from her "burrow" (She was rescued from a high kill shelter. For whatever reason, kennels have a bad association for her, but she made her own little burrow out of a space under a coffee table.) Once in a while though, a little spray goes off the pad.
So anyway, I smell pet urine on a pretty frequent basis. I'm obsessive about cleaning it off everything. Baking soda, vinegar, peroxide, and pet enzyme live in big bottles in my house!
If I smell something early on the day, the smell just STAYS in my nose the rest of the day. I just can't keep from smelling it!
It's totally psychosomatic, and I KNOW it's in my head, but I'm obsessively sniffing all day long!
On a "sinus" related front though, right before I'm about to get a cold, I occasionally smell really STRONG laundry detergent perfume, in my nose.