ISO/TR 27628:2007 contains guidelines on characterizing occupational nanoaerosol exposures and represents the current state-of-the-art, with an emphasis on nanometre-diameter particles. Background information is provided on the mechanisms of nanoaerosol formation and transportation within an occupational setting and on industrial processes associated with nanoaerosol exposure. Exposure metrics appropriate to nanoaerosols are discussed, and specific methods of characterizing exposures with reference to these metrics are covered. Specific information is provided on methods for bulk aerosol characterization and single particle analysis.