:: Section 9 of 10
II. SAMPLING METHODS: IMPACTOR
Common methods of viable bioaerosol sampling include impactors, impingers, and filtration.
Impactors utilize the bioaerosol inertia to collect the bioaerosol onto a solid or semi-solid collection medium. The impactor forces the air stream to turn a tight corner. If the inertia of the bioaerosol is too great, the bioaerosol will not be able to follow the air flow lines and will instead impact onto the collection medium.
Figure 12: The principle of impaction.
Please visit the Aerosol Transport - Inertia online module to learn more about the principle of impaction. Once the bioaerosols are collected onto the collection medium, they can be cultivated to determine the viable count. Multi-stage impactors can be used to collect a wide range of bioaerosol sizes. Because the impactor utilizes inertia to physically collect particles, its physical collection efficiency is highly dependent on particle size.
Figure 13: A demonstration of the use of multi-stage impactors.