Silent But Deadly! unfortunately an all too familiar odor eminating mysteriously around groups of people, survivable outdoors, but toxic in an enclosed space, in which everyone looks around trying to figure out who let rip (even the smirking perpetrator).
sitting in the back of a pick-up truck with a group of friends on our way to lollapalozza, when suddenly the driver's side window rolls quickly down and the driver sticks his head out the window screaming "S.B.D.!S.B.D.!" dousing the front cab with ozone, while the guy riding shotgun is laughing his guilty arse off. if especially deadly, DO NOT be stuck downwind, i.e. in this case, riding in the back of an open truck slowly, or worse, trapped in the car itself.