The application of a virtual impactor to modify the overall sensitivity function of an aerosol photometer has been studied. The measurement of particles in the minor airflow of a virtual impactor results in a significant increase in the photometer's sensitivity to large particles. The increased response to large particles is considered as a change in the sensitivity function. The location of the overall sensitivity maximum can be shifted from the submicrometer-size range to the 2–3 µm region (the region where the particle deposition in human lungs is high).
Lehtimäki, M., & Keskinen, J. (1988). A method of modifying the sensitivity function of an aerosol photometer. American Industrial Hygiene Association Journal, 49(8), 396-400. https://doi.org/10.1080/15298668891379963