Which pairing of device and flow rate is correct?

• A. Air-O-Cell Cassette — 15 lpm
• B. Andersen N6 — 15 lpm
• C. Air-O-Cell Cassette — 28.3 lpm
• D. Andersen N6 — 28.3 lpm

Answer: (A)

Understanding device-specific flow rates is essential in bioaerosol sampling: each sampler is calibrated to collect particles optimally at a particular velocity, which in turn affects how many organisms deposit on the collection medium and how they are distributed for counting. The Air-O-Cell Cassette is designed to operate at a relatively gentle, standard flow of 15 liters per minute. This rate provides a stable deposition of bioaerosols onto the culture slide inside the cassette, producing reliable colony counts without overloading or under-sampling the slide.

In contrast, the Andersen six-stage sampler is calibrated for a higher flow, typically 28.3 liters per minute, to achieve its stage-by-stage size separation. Using a flow rate of 15 L/min with the Andersen would shift the aerodynamic cutoffs and disrupt the intended size-resolved collection, leading to inaccurate results.

Therefore, the pairing of Air-O-Cell Cassette with 15 L/min is the correct match: it aligns with the device’s validated operating conditions, ensuring accurate collection and meaningful CFU counts. The other pairings involve flow rates that are not appropriate for the respective devices, which is why they’re not correct.