I'm afraid Rio doesn't follow that rule! She's a girl and she lets out the silent but deadly ones all the time - especially if I happen to be cuddling with her and her little butt is near my face!
I can't believe such a foul smell can come from that sweet little furball! She doesn't toot a lot, but when she does - Man, watch out! We're getting a baby brother for her in a couple of months - wonder if he'll be just as "aromatic!"