An advanced analytical chemistry laboratory experiment is described that involves environmental analysis and gas chromatography-mass spectrometry. Students analyze lint from clothes dryers for traces of flame retardant chemicals, polybrominated diphenylethers (PBDEs), compounds receiving much attention recently. In a typical experiment, ng/g levels of three PBDE congeners (#47, #99, and #100) were found in the dryer lint through use of several mass spectral modes: negative chemical ionization-selected ion monitoring (MS-NCI-SIM) and tandem mass spectrometry with electron ionization and selected reaction monitoring (MS-EI-SRM). Students gain experience in Soxhlet extraction, mass spectrometry, and isotope dilution analysis as they explore their own local environments. (Contains 2 tables.)