In pharmaceutical, biotech and microelectronics industries, airborne particle monitoring is a cornerstone of contamination control.
Selecting the right particle counter for your cleanroom means ensuring regulatory compliance, product quality and process safety.
In this article, we will explore:
- the different technologies (optical, condensation, diffraction)
- how to choose the right system for your ISO/GMP classification
- common mistakes to avoid during design and validation
What Is a Cleanroom Particle Counter?
A particle counter is a device used to measure the concentration and size of non-viable particles in the air of a controlled environment, such as:
- ISO 14644 cleanrooms (Class 1 to 9)
- GMP Grade A/B/C/D environments (EU Annex 1)
- Isolators and RABS
- Microbiology, semiconductor and aerospace labs
The instrument samples air and detects solid particles, often ≥0.3 µm, reporting their count per cubic meter or per liter.
Types of Particle Counters: Optical, Condensation, Diffraction
1. Optical Particle Counter (OPC)
The most widely used. A laser beam hits the particles, and a photodetector measures the scattered light.
Best for:
- Real-time measurement
- Range: >0.3 µm
- ISO 14644 and GMP-compliant monitoring
Limitation: not ideal for ultrafine particles (<0.1 µm)
2. Condensation Particle Counter (CPC)
Particles are enlarged by condensation to enable detection.
Best for:
- Detecting ultrafine particles (>0.01 µm)
- ISO Class 1–2 environments
Limitation: more complex, maintenance-intensive, rarely used in pharma GMP
3. Diffraction-based Counters
Measure particles by analysing angular light scattering.
Niche use:
- Scientific research, specific industrial applications
Not commonly used for GMP compliance
The Importance of Sampling Flow Rate
Flow rate is a critical parameter in particle counting, as it directly impacts the time needed to collect the required volume (e.g. 1 m³) and the suitability of the measurement for regulatory purposes.
-
1 CFM = 2.83 LPM
Typical of handheld or compact portable units. Useful for troubleshooting, spot checks and quick investigations. Not suitable for GMP qualification: collecting 1 m³ would take more than 6 hours. -
1 CFM = 28.3 LPM
The international standard, derived from FED-STD-209 and maintained in ISO 14644 and EU GMP Annex 1. It is the minimum acceptable flow rate for cleanroom qualification and the most common for both portable units and fixed remote sensors in continuous monitoring. -
50 LPM = 1.77 CFM
Introduced to shorten the sampling of 1 m³ from about 36 minutes to 20 minutes. Widely used in pharma, especially for critical point qualification as required by Annex 1. -
100 LPM = 3.53 CFM
Further reduces sampling time to about 10 minutes for 1 m³. Favored in semiconductor manufacturing (many points to monitor) and in high-throughput pharma, where downtime reduction is essential. These systems are more expensive and require robust optical designs.
Application guidelines:
- Pharma GMP / Annex 1 → minimum 1 CFM (28.3 LPM). Higher flow rates (50 or 100 LPM) are often used to reduce downtime, but the total volume must always be ≥1 m³.
- Semiconductors / microelectronics → stricter requirements in terms of sensitivity and time. 50–100 LPM instruments are preferred, while fixed systems often rely on 1 CFM for consistency.
- Handheld devices → limited to 0.1 CFM, useful for quick checks but not valid for formal qualification.
5 Key Criteria to Select the Right Sensor
1. Cleanroom Classification (ISO or GMP)
- ISO 5 / GMP Grade A: high-sensitivity sensor (0.3 µm or less)
- ISO 7 / GMP Grade C–D: standard optical counter is sufficient
2. Monitoring Type: Continuous vs. Spot Checks
- Continuous monitoring (as per Annex 1): fixed sensors with data logging
- Spot checks: portable counters for routine validation or troubleshooting
3. Regulatory Requirements
- ISO 14644-1:2015
- EU GMP Annex 1 (2022 revision)
- FDA CFR 21 Part 11 (for electronic records)
4. Installation Environment
- Temperature, humidity, chemical compatibility
- Integration with BMS/EMS or SCADA systems
5. Validation & Maintenance
- Calibration traceability (ISO 21501-4)
- Easy-to-validate data
- Local technical support
Common Mistakes to Avoid
- Using the wrong detection range for your cleanroom class
- Employing handheld sensors in environments requiring continuous monitoring
- Skipping ISO 21501-4 compliance, which is critical for GMP validation
- Failing to integrate data into centralized systems
QSGroup Solutions
QSGroup offers:
- Expert support in choosing GMP-compliant particle counters
- Design, installation and qualification (DQ/IQ/OQ) of fixed or portable units
- Setup of validated environmental monitoring systems (EMS)
- ISO 21501-4–certified calibration and service plans
Our cleanroom monitoring systems are tailored to your ISO/GMP classification, with full documentation for audits.
Final Thoughts
Choosing the right particle counter for your cleanroom is more than a technical choice—it’s a strategic decision. It affects regulatory compliance, process control and overall product safety.
With QSGroup as your partner, you’ll benefit from validated instrumentation, technical expertise and end-to-end GMP support.
