Im not positive how to answer because everyones sensitivity to smells is different, but from what I hear, when they have parasites its REALLY bad! Like, it makes you gag, that bad. My Norbert has been tested and came back negative for parasites and his stool still smells disgusting.
My boy has watery soft stool that can clear a room. I can tell when he poops even from the other side of the living room, just by smell alone. I'm pretty certain my boy has parasites. He see's a vet friday. I read if the smell can "clear a room" then you should have a stool sample tested.