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Chapter 74 : Sampling for Airborne Microorganisms
This chapter presents various bioaerosol sampling and analysis methods to facilitate the selection of instrumentation and techniques. The principles of bioaerosol sampling are presented, followed by a review of sampling methods and techniques currently available, including the results of performance evaluations of the various sampler types. Equipment calibration and air sampling considerations such as collection times and the number of samples are discussed. Measurement of airborne microorganisms with a bioaerosol sampler often aims at documenting the presence of specific sources. The impaction method separates particles from the air stream by utilizing the inertia of the particles to force their deposition onto a solid or semisolid collection surface. Liquid impingement is similar to impaction in that the inertial force of the particle is the principal force removing it from the air. Filtration achieves the separation of particles from the air stream by passage of the air through a porous medium, usually a membrane filter. The collection of airborne microorganisms onto a filter material is used in bioaerosol monitoring due to its simplicity, low cost, and versatility. Validation of surface sampling methods and the development of standardized sampling and analysis protocols are vital for the detection of biothreat agents, the determination of their concentration and distribution, and the evaluation of the effectiveness of remediation procedures.
Mechanisms of collection utilized in bioaerosol sampling. (A) Solid plate impaction; (B) centrifugal impaction; (C) liquid impingement; (D) filtration. Fin or Finertial, inertial force. (Adapted from reference 111 with kind permission from Elsevier Science Ltd., Kidlington, United Kingdom.)
Collection times for selected bioaerosol samplers. BURK, Burkard spore trap (personal sampler); AND, Andersen six–stage viable impactor sampler; AND-VI, sixth stage of the Andersen six-stage impactor used as a separate sampler; MK-II, Casella MK-II sampler; SAS, surface air system high-flow sampler. (Adapted from reference 111 with kind permission from Elsevier Science Ltd., Kidlington, United Kingdom.)
General characteristics of several commercially available bioaerosol samplers
Calculated and reported cutoff diameters (d50s) for several commercially available bioaerosol samplers