Exhaust fumes, like the atmosphere they flow into, are mostly invisible and easy to keep out of mind, but if that Silverado’s tail pipe were directed back into the vehicle, the driver and all her passengers would be dead in minutes. If the Silverado’s exhaust were piped into the driver’s living room, she and her family would be dead in an hour. But somehow, when we run our cars “outside,” in our shared atmosphere, all the soot and toxic gases magically disappear.
