Difference Between Viable and Non-Viable Particles: Definition, Examples, Detection Methods, and Cleanroom Importance

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In pharmaceutical cleanrooms and controlled environments, particle monitoring plays a crucial role in ensuring product sterility and environmental control. Every cleanroom contains two types of particles — viable and non-viable. Understanding their differences, measurement methods, and significance is essential for maintaining compliance with GMP (Good Manufacturing Practices) and ISO cleanroom standards.

What are Viable and Non-Viable Particles?

Viable Particles

Viable particles are living microorganisms that have the potential to grow and reproduce under suitable conditions. These include bacteria, fungi, yeast, and spores. They can contaminate sterile products, media, and critical areas during pharmaceutical manufacturing or microbiological testing.

In cleanrooms, viable particles are mainly generated from human operators, unfiltered air, equipment surfaces, and raw materials. Since viable particles can multiply, their control is essential for preventing microbial contamination.

Non-Viable Particles

Non-viable particles are non-living particulate matter such as dust, fibers, or aerosols that do not contain any viable microorganisms. However, these particles can act as carriers or substrates for viable microorganisms. Therefore, monitoring non-viable particles is equally important to maintain a clean environment.

Common sources include equipment movement, personnel clothing, material transfer, and HVAC system leaks.

Key Differences Between Viable and Non-Viable Particles

Parameter Viable Particles Non-Viable Particles
Nature Living microorganisms (bacteria, fungi, spores) Non-living particles (dust, fibers, aerosols)
Reproduction Can multiply and grow under suitable conditions Cannot reproduce or grow
Detection Method Microbial air sampler, settle plates, contact plates Particle counter or electronic particle analyzer
Measurement Unit CFU (Colony Forming Units) Particles per cubic meter (≥0.5 µm, ≥5.0 µm)
Source Humans, raw materials, HVAC air, equipment Dust, fibers, mechanical wear, air turbulence
Effect on Product Can cause microbial contamination May act as carrier of viable particles
Control Method Disinfection, sterilization, gowning, HEPA filtration Air filtration, housekeeping, laminar airflow control

Detection and Measurement Methods

1. Viable Particle Monitoring

Active Air Sampling: Uses microbial air samplers such as sieve impaction or slit-to-agar samplers that impact a known volume of air onto nutrient agar. After incubation, microbial colonies are counted as CFU/m³.

Passive Air Sampling: Employs settle plates exposed to the environment for a fixed time to collect airborne microorganisms by gravity.

Surface Sampling: Performed using contact plates or swabs to detect viable organisms on surfaces, walls, or equipment.

2. Non-Viable Particle Monitoring

Electronic Particle Counters: Instruments that measure airborne particles based on light scattering or light obstruction principles. The most common device is a Laser Particle Counter, which counts particles ≥0.5 µm and ≥5.0 µm sizes per cubic meter of air.

Non-viable particle monitoring is performed continuously or periodically in cleanrooms, particularly during cleanroom qualification and routine operation.

Importance of Monitoring Viable and Non-Viable Particles

Monitoring both particle types helps to ensure that cleanroom environments remain within the acceptable contamination limits specified in ISO 14644-1 and EU GMP Annex 1.

  • Ensures compliance with regulatory cleanroom standards
  • Prevents microbial contamination of sterile products
  • Validates HVAC and HEPA filtration performance
  • Provides environmental trend data for risk assessment
  • Helps identify contamination sources and corrective actions

Acceptance Criteria for Cleanroom Monitoring

The cleanroom classification for both viable and non-viable particles is defined by ISO 14644-1 and EU GMP Annex 1 as follows:

Non-Viable Particles (Airborne Particulate Classification)

Grade ≥0.5 µm (Particles/m³) ≥5.0 µm (Particles/m³)
Grade A 3,520 20
Grade B 35,200 290
Grade C 352,000 2,900
Grade D 3,520,000 29,000

Viable Particles (Microbial Contamination Limits)

Grade Air Sample (CFU/m³) Settle Plate (CFU/4hr) Contact Plate (CFU/plate) Glove Print (CFU/glove)
Grade A <1 <1 <1 <1
Grade B 10 5 5 5
Grade C 100 50 25 Not Defined
Grade D 200 100 50 Not Defined

Conclusion

Both viable and non-viable particles are critical indicators of cleanroom environmental control. Viable particles represent biological contamination risks, while non-viable particles act as carriers that may compromise product sterility. Continuous monitoring, proper HVAC design, and strict adherence to cleanroom gowning and cleaning protocols ensure a contamination-free environment compliant with GMP and ISO standards.

In summary: Understanding and differentiating between viable and non-viable particles is the foundation of an effective cleanroom contamination control strategy.

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