Robert Boynton, air quality instrument specialist at the Bay Area Air Quality District monitoring station, uses computers to record data on particulate
Robert Boynton, air quality instrument specialist at the Bay Area Air Quality District monitoring station, uses computers to record data on particulate matter from the air collected on the roof of this building in San Pablo, Calif., on Monday, March 25, 2013. Real time samples are taken and also samples every six days over a 24-hour period are recorded on a special paper filter and analyzed. (Susan Tripp Pollard/Staff)