Idle Hands.(The Talk of the Town)(monitoring air quality; idling drivers)

If you go to school in Bushwick, Brooklyn, you may have noticed, alongside the cotton-candy sellers and the babysitters who gather on the curb around 3 P.M., several academic-looking women making notes on clipboards. The clipboards are covered with voter-registration stickers, though if you ask the women about voting, or anything else--where the lunchroom is, when the third graders get out--you'll be met with blank stares and a vague answer: "We're not with the school" or "We're studying the air."

The women belong to a nonprofit group called the Asthma Free School Zone, which, for the past year, has been holding covert stakeouts of schools around the city to aid a campaign against vehicle idling. New York City prohibits idling for spurts of longer than three minutes (the fine is from three hundred and fifty to two thousand dollars), though the law is rarely enforced. In 2004, after receiving a tip from the A.F.S.Z., Eliot Spitzer, who was the attorney general at the time, sued several school-bus companies for breaking the rule, and last month, as governor, Spitzer signed a ban on all bus idling in school zones. "In Switzerland you have to turn your engine off if you're more than four cars behind the stoplight," Rebecca Kalin, the group's founder, said the other day. "Idling is rude there. It's like burping--you just don't do it."

Kalin had arrived at P.S. 274 a little before two o'clock, with three colleagues: Lori Bukiewicz, a public-health worker; Jen Richmond-Bryant, an assistant professor at Hunter College (courses: Ventilation, Indoor and Outdoor Air Quality); and Bin-Yun Zheng, the group's assistant. When no one was looking, they wheeled out a small gray cabinet with a plastic tube sticking out of the top. The cabinet emitted a low buzzing noise, and it contained a car battery, two Sidepaks--used to gauge air quality by counting small particles called PM2.5--and an instrument called an Aethelometer, which measures black carbon. They attached an additional Sidepak to the belt of Desiree Maldonado, a crossing guard and an accomplice. "My role is wearing this gadget for as long as I'm out here," Maldonado said, pointing to the device on ...