Denver Post: In a forest just off the Continental Divide, Duane Kitzis runs a federal government air-collecting operation — trapping the relatively fresh air here at 10,000 feet and storing it in hundreds of aluminum cans. The 4-foot-tall cans, called “standards,” are used to calibrate machines that measure the pollution people put into the atmosphere. The lab has been designated by the United Nations World Meteorological Organization as the Central Calibration Laboratory for …