ANALYTICAL & LAB EQUIPMENT Small-scalesampling
A paper written by Mark Hallworth from PMS explores sampling techniques in cleanrooms and associated controlled environments
Graph of particle losses in tubing
A venn diagram showing the ISO 14644-21 contamination control strategy T
he following article is an excerpt from the paper: ISO/TR 14644-21:2023 Cleanrooms and Associated
Controlled Environments: Airborne Particle Sampling Techniques, written by industry expert and ISO 14644 Technical Committee member Mark Hallworth of Particle Measuring Systems. It is an essential guide designed to help cleanroom operators and technicians refi ne their airborne particle sampling methods. The full paper is complete with specifi c requirements, explanatory diagrams and a decision tree. This technical report (TR21) was
developed in response to updates in the EU GMP Annex 1 regulation regarding sterile medicinal product manufacturing. It provides a comprehensive discussion on classifi cation and monitoring strategies for maintaining cleanroom
air quality and minimising particle contamination.
IMPORTANCE OF PARTICLE COUNTING Cleanrooms are controlled environments where airborne particle concentration must be continuously monitored to meet standards, such as ISO 14644, required by regulatory bodies. Importantly, ISO/TR 14644- 21 discusses the importance of accurately detecting and measuring smaller particles, which also pose signifi cant contamination risks.
CHALLENGES IN PARTICLE SAMPLING ISO/TR 14644-21 identifi es three primary areas of concern when sampling airborne particles: 1. Sampling errors: These errors
ISP isokinetic sampling diagram 18
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occur when the sample taken does not accurately represent the total air volume in the cleanroom. ISO/TR 14644- 21 stresses the importance of isokinetic sampling, where the air velocity at the sample inlet matches the room’s airfl ow. If this balance is not achieved, particles might be under or over-sampled, leading to inaccurate results. 2. Sample measurement errors: These errors stem
from the equipment used in particle counting. Light Scattering Aerosol Particle Counters (LSAPCs) are the most commonly used instruments. Particle coincidence, impact of optical contamination and accurate calibration of LSAPCs, based on ISO 21501-4, are crucial for reliable results. 3. Sample transportation errors:
When using tubing to transport air samples to a particle counter, particle losses can occur due to tubing bend sedimentation, electrostatic attraction, and Brownian motion. ISO/TR 14644- 21 gives specifi c advice for keeping tubing lengths short and using smooth-bore materials to minimize these losses.
CONCLUSION ISO/TR 14644-21:2023 off ers valuable guidance for both cleanroom classifi cation and monitoring, with a focus on minimising errors in airborne particle sampling. By understanding and addressing the potential sources of error in particle sampling and transportation, cleanroom operators can better maintain control over their environments, ensuring compliance with regulatory standards and minimising contamination risk.
For more information visit:
www.pmeasuring.com
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