The Essential Guide to Cleanroom Air Filtration Systems

Cleanrooms are controlled environments with extremely low levels of pollutants and particles. They are used in industries like pharmaceuticals, medical devices, semiconductors, and aerospace where quality and purity are critical. The air filtration system is the heart of any cleanroom. It removes contaminants and provides a constant supply of clean air to maintain cleanroom specifications. This article provides a comprehensive guide to understanding cleanroom air filtration.

What is a Cleanroom?

A cleanroom is a controlled environment designed to minimize contamination from airborne particles, chemical vapors, and microbes. Some key features include:

Cleanroom Standards

Cleanrooms follow stringent standards for particulate counts based on the room class. The ISO 14644-1 standard defines maximum concentration limits for different cleanroom classes. The lower the class number, the cleaner the room.

Cleanroom Classifications

Cleanrooms are classified from ISO Class 1 to ISO Class 9 based on the number of particles of size 0.1 μm or larger permitted per cubic meter. For example, a Class 5 cleanroom cannot exceed 3,520 particles/m3.

Why is Air Filtration Vital in Cleanrooms?

Maintaining ultraclean air is critical in cleanrooms for two main reasons:

Contaminants in Cleanrooms

Dust, microbes, skin cells, fibers, and more can enter cleanrooms and damage products. Air filtration removes these harmful particles.

How Contaminants Enter Cleanrooms

People, processes, and poor air quality allow contaminants to enter. Robust air filtration is essential to remove pollution.

Cleanroom Air Filtration System Components

Specialized air filters clean and recirculate air in cleanrooms. Key components include:

Pre-filters

Remove large particles like hair and fibers. Protect downstream filters.

HEPA Filters

HEPA (High Efficiency Particulate Air) filters remove 99.97% of particles ≥0.3 μm. Critical for cleanrooms.

ULPA Filters

ULPA (Ultra Low Penetration Air) filters are more efficient than HEPA. They remove 99.999% of particles ≥0.12 μm. Used in higher class cleanrooms.

Carbon Filters

Adsorb gaseous chemical contaminants like VOCs.

Fan Filter Units

Blowers recirculate air through filters back into the cleanroom. Mounted on ceilings or walls.

Designing an Effective Cleanroom Air Filtration System

Proper cleanroom design optimizes air quality. Key factors include:

Airflow Patterns

Unidirectional flow removes particles. Laminar flow is smooth, parallel streams.

Calculating Air Changes per Hour

Higher air changes per hour increase cleanliness. Minimum rates are defined by ISO standards.

Air Pressure Differentials

Positive pressure in cleanrooms forces air outwards preventing contamination ingress.

Humidity and Temperature Controls

Conditions are maintained within tight limits to avoid filter degradation.

Maintaining Cleanroom Air Filtration Systems

Cleanroom air filtration systems require careful maintenance including:

Filter Replacement Schedule

HEPA filters are changed based on pressure drop across them. ULPA filters are replaced more frequently than HEPA.

Validating System Performance

Cleanliness is verified via particle counting and airflow visualization. Filters are integrity tested.

Monitoring Critical Parameters

Temperature, humidity, pressure differentials, and power status are monitored 24/7. Alarms alert operators.

Key Takeaways on Cleanroom Air Filtration

• Robust air filtration is crucial for cleanrooms to control particulates.

• HEPA or ULPA filters combined with laminar airflow provide ultraclean environments.

• Strict protocols validate performance and ensure standards are continuously met.

• Proper design, operation and maintenance are essential for cleanroom integrity.

Cleanroom Air Filtration System FAQs

What are the different cleanroom classifications?

Cleanrooms are classified ISO 1 to ISO 9 based on maximum permitted particle counts from 0.1 to 5.0 μm size. Lower ISO classes are cleaner.

How often should cleanroom HEPA filters be replaced?

HEPA filters should be changed when the pressure drop exceeds specified limits, typically around 2.0-3.0 inches w.g. This may be every 9-12 months.

What is the difference between HEPA and ULPA filters?

ULPA filters remove 99.999% of particles ≥0.12 μm while HEPA filters remove 99.97% of particles ≥0.3 μm. ULPA filters are more efficient for higher cleanroom classes.

How can cleanroom air filtration systems be validated?

Systems are validated by particle counting, airflow visualization tests, filter leak tests, and monitoring critical parameters like pressure differentials.

Why is humidity control important in cleanroom air filtration?

Low humidity can damage filters while high humidity encourages microbial growth. ISO standards define optimal RH between 30-60% for cleanrooms.