Which statement best describes the device known for viable air sampling?

• A. Multiple hole impactionor
• B. Impactor with a single hole
• C. Liquid impinger
• D. Gelatin filter

Answer: (A)

The key idea is capturing living microorganisms for counting, so the device used is an impactor that deposits viable organisms onto a growth medium. A multiple-hole impactionor, like the classic Andersen-type sampler, uses several small holes through which air is drawn. As particles are accelerated and strike the agar surface in each stage, viable microorganisms are kept alive long enough to grow into colonies. The stage-by-stage arrangement also helps separate particles by size, giving information about which particle ranges carry viable microbes.

This is why the multiple-hole impactionor is the best description. A single-hole impactionor wouldn’t provide the same size-segregated collection, a liquid impinger collects into liquid rather than onto a solid plate for CFU counting, and a gelatin filter is a filter-based method rather than an impactor designed for staged, viable collection on agar.