Development and Application of a Low-Flow Thermodenuder

This compilation describes the development and application of a thermodenuder (TD). Such an instrument enables near real-time measurements of total volatile and non-volatile particle concentrations of combustion aerosols by conditioning exhaust emissions in the ultrafine (nanometer) particle regimes. The TD is designed to strip-off the volatile and semi-volatile fraction (short-chained hydrocarbons) attached to the surface of particles by thermal desorption. Innovative aspects of this instrument include the direct heating system (based on a galvanically separated power unit) and the registration of the internal gas temperature. Both features keep the temperature gradient stable and, at the same time, prevent unexpected sample transformations due to uncontrolled condensation and re-nucleation under supersaturated conditions. The TD is suitable for use with instruments like Scanning Mobility Particle Sizers (SMPS) or Electrical Low Pressure Impactors (ELPI), has the potential to monitor combustion devices with respect to future environmental directives, and aids in the maintenance and proper functioning of existing fossil fuel powered devices.