An aerosol concentrator is a vital component of any front-end sampling module used to introduce aerosol particles to a chemical or biological identification sensor (Hart et al, 2000). Because these sensors need to have a minimum amount of sample to make a positive identification, particle concentration is often necessary, making it critical to know the concentration factor of the aerosol concentrator as a function of particle aerodynamic diameter. Traditional experimental techniques rely on fluorometric analysis of particles collected from the minor and major flows of the virtual impactor as well as particles recovered from the internal walls of the concentrator (Romay et al., 2002). While this technique allows one to obtain a complete mass balance of the particles that enter the concentrator, it is time-consuming and labor intensive.
This paper shows alternative concentration factor measurements using a real-time aerosol spectrometer. While results are obtained quickly with this technique, it is important to recognize several artifacts that are possible when using real-time spectrometers, such as particle coincidence in the spectrometer, particle losses in sampling lines, and getting a representative upstream aerosol sample. Measurements of the aerosol concentration factor as a function of particle diameter have been made with a two-stage 1-um concentrator (Romay et al., 2003) with a total sampling flow rate of 250 L/min and a minor flow rate of 1.0 L/min