light stink
natural gas is colorless, odorless, and tasteless. the stuff that leaks out of your gas line sure isn't. they add a stinky smell to it. specifically so people can tell when there's a gas leak. it's a pretty good idea. if it stinks that bad, it must be dangerous enough to kill you. whereas if it's just a little stinky or just a little unsightly, like pollution from a coal burning power plant, it must be perfectly safe. however, if it's a completely invisible poison it must be incredibly deadly. like radiation. it's kinda too bad we can't make radiation stinky. or visible. or stinky and visible. but just a little. then folks wouldn't be afraid of it. heh. i'd be so rich. ah well.