, so that your clothes soak up these poisons while you walk along.Two pairs of jeans could apparently clean up the nitrogen oxides from one car. And you wouldn't be able to see or feel anything different.Now for the words. Simon Armitage, who's professor of poetry at the university, has written a poem to go on the poster. It's called "In Praise of Air" (see box).The poster will be on display in Sheffield for the next year.