Direct comparison
Viable Air Sampler: Active vs Passive Guide
Compare viable air sampler types (impaction, centrifugal, filtration, settle plates) for GMP/USP environmental monitoring procurement decisions.
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Side-by-side comparison
| Dimension | Active: Impaction (Agar Plate) | Active: Centrifugal | Active: Membrane Filtration | Passive: Settle Plate |
|---|---|---|---|---|
| Sampling principle | Air drawn through a slit or perforated head, impacts directly onto agar | Rotating impeller flings air onto an agar strip | Air drawn through a sterile membrane filter, then plated | Passive gravitational deposition onto an open plate |
| Result type | Quantitative CFU/m³ from a known air volume | Quantitative CFU/m³ from a known air volume | Quantitative CFU/m³, tolerates larger volumes | CFU per plate per exposure time (not a volumetric result) |
| Typical plate/media | Standard 90mm contact/settle plates, flexible sourcing | Manufacturer-proprietary agar strips | Sterile membrane + separate growth medium | Standard open settle plates |
| Best-fit zone | General GMP EM program workhorse, all grades | Fast handheld rounds, space-constrained areas | Lower-classification or longer sampling runs | Continuous coverage during active operations, all grades |
| Disruption risk in Grade A/B | Low if fixed/remote-triggered; moderate if handheld | Moderate — handheld operation typical | Moderate — handheld operation typical | Minimal — no active operator intervention needed |
| Consumable cost/lock-in | Low — open plate market | Higher — proprietary strips | Moderate — filter plus media | Low — open plate market |
Common questions
FAQ
Is a settle plate technically an air sampler?+
Not in the volumetric sense — it has no pump and produces no CFU/m³ result. It is nonetheless the passive half of most viable environmental monitoring programs and is typically procured and qualified alongside active samplers.
Which method recovers stressed or fragile microorganisms best?+
This varies by product and is governed by the impaction velocity and particle-size cut-off (d50) of the specific unit. Ask manufacturers for published recovery-efficiency data and validate against your own reference organisms during qualification rather than assuming one principle is universally gentler.
Going deeper
