General view of an unidentified laboratory technician operating a Perkin-Elmer Model 303 Atomic Absorption Spectrophotometer at an Environmental Protection Agency facility. Per notations accompanying the photograph, the atomic absorption spectrophotometer is being used to measure the amount of mercury in an atmospheric sample, part of the work of the EPA's Division of Atmospheric Surveillance. Notably, the silver plates visible in racks along the wall are used to form an amalgam with any mercury present in the room's air in order to ensure an accurate read of the sample.