In controlled environments such as cleanrooms, laboratories, and GMP pharmaceutical areas, microbiological air sampling plays a critical role in monitoring the microbial quality of the air and ensuring compliance with international standards, like Annex 1, ISO 14698, and USP <1116>.
But not all air samplers are the same — and choosing the right one for your application can directly affect the reliability, sensitivity, and regulatory acceptance of your monitoring strategy.
This guide compares the three main sampling technologies — impaction, filtration, and centrifugation — to help you make the best choice for your cleanroom.
Why airborne microbiological sampling matters
Air can be a major vector of contamination, especially in aseptic processing areas. Microorganisms can be carried by dust particles, droplets, or personnel, and even small deviations from microbial control can lead to batch rejection, regulatory findings, or product recalls.
Standards such as:
- EU GMP Annex 1 (2022)
- ISO 14698-1:2003
- USP <1116>
require proactive and risk-based environmental monitoring programs, where air samplers are essential tools for active microbiological surveillance.
Types of microbiological air samplers: an overview
1. Impaction samplers (1-Stage or 2-Stage)
How it works: Air is drawn through a perforated plate and impacts directly onto a culture medium (e.g., agar). Viable microorganisms are retained and later incubated for colony forming units (CFU) counting.
Advantages:
- High regulatory acceptance (Annex 1 compliant)
- Direct culture of viable organisms
- Immediate correlation between air sample and result
Limitations:
- Limited volume (e.g., 1000 L per sample)
- Can dehydrate agar if sampling time is long
Best for: Grade A/B cleanrooms, critical zones, aseptic filling areas
2. Filtration samplers
How it works: Air is pulled through a membrane filter that retains microorganisms. After sampling, the filter is placed onto culture media for incubation.
Advantages:
- Allows sampling of larger volumes over time
- Suitable for harsh or high-humidity environments
- Useful when agar-based systems are not viable
Limitations:
- More complex handling and transfer
- Longer incubation time
- Risk of desiccation or loss of viability during sampling
Best for: HVAC systems, compressed gases, large-volume sampling
3. Centrifugal samplers (e.g., Slit-to-Agar or Andersen type)
How it works: Air enters a rotating sampler and particles are driven by centrifugal force onto an agar surface.
Advantages:
- Historically well studied
- Simulates real-time air exposure
- Cost-effective options available
Limitations:
- Less precise than impaction
- Harder to standardize sample volume
- Limited documentation in newer GMP guidance
Best for: Non-classified environments, background monitoring, educational or legacy facilities
Key factors to consider when choosing an air sampler
| Factor | Impaction | Filtration | Centrifugation |
| Regulatory compliance | High | Moderate | Low |
| Sample traceability | High | Moderate | Limited |
| Ease of use | Yes | Requires transfer | Simple |
| Sample volume | Limited | High | Variable |
| Suitability for aseptic area | Yes | With precautions | Not recommended |
QSGroup recommendations
For environments subject to Annex 1 and ISO 14698, QSGroup recommends:
- Impaction samplers for Grade A/B environments
- Filtration samplers for HVAC, background areas, and gas systems
- Avoid centrifugal systems in GMP-classified areas unless justified
Each sampling device should be:
- Calibrated and validated
- Integrated into an Environmental Monitoring Plan (EMP)
- Accompanied by proper SOPs and personnel training
Need help choosing the right air sampler?
QSGroup provides consulting, validated air samplers, and EMP planning tailored to pharmaceutical and biotech facilities.
Whether you are upgrading to Annex 1:2022 or designing a new cleanroom monitoring strategy, our specialists can support you.
Contact us to receive a sampler comparison chart or request a technical consultation.
