When lying in bed with your spouse, you grab her/him tightly, wrap yourselves completely in the blanket, and rip ass. It causes the fart in the air to become highly
concentrated and, since you and your spouse are so close to each other, the
temperature rises, further strengthening the fart. Meanwhile, your spouse is unable to move, which forces her/him to smell it. You
of course are immune to your own farts.