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Air Shower Design for Cleanrooms: Key Principles and Engineering Considerations
Created on 02.05
Air showers are a critical component of cleanroom contamination control systems. Positioned at the interface between non-controlled and controlled environments, air showers remove surface-borne particles from personnel or materials before entry into clean areas.A well-designed air shower not only improves cleanroom performance but also supports compliance with ISO 14644 and GMP requirements. This article outlines the key principles and engineering considerations for effective air shower design in cleanroom applications.
1. The Role of Air Showers in Cleanroom Contamination Control
Personnel movement is one of the primary sources of particulate contamination in cleanrooms. Even with proper garments, particles attached to clothing and exposed surfaces can be carried into critical areas.
Air showers function by:
Delivering high-velocity, HEPA-filtered air to dislodge particles
Creating a controlled transition zone between cleanroom classifications
Reducing particle load before personnel or materials enter the cleanroom
Proper air shower design ensures this process is effective, repeatable, and does not disrupt cleanroom pressure balance.
2. Airflow Design Principles
2.1 Air Velocity and Effectiveness
Air velocity is a key determinant of particle removal efficiency.Typical design parameters include:
Nozzle air velocity: 20–25 m/s
Effective air showering time: 10–20 seconds per cycle
The goal is to generate sufficient shear force to remove particles without causing discomfort or re-entrainment of contaminants.
2.2 Nozzle Layout and Coverage
Uniform airflow coverage is essential. Engineering considerations include:
Multi-directional nozzle arrangement (side walls, corners, or ceiling)
Overlapping air streams to eliminate dead zones
Adjustable nozzles to accommodate different cleanroom garments
Poor nozzle placement can lead to uneven cleaning and reduced contamination control efficiency.
3. Filtration System Design
3.1 HEPA Filtration Requirements
Air showers typically use HEPA filters (H13 or H14) to ensure high air cleanliness:
H13: ≥99.97% efficiency at 0.3 μm
H14: ≥99.995% efficiency at 0.3 μm
Filter selection should align with the cleanliness class of the downstream cleanroom.
3.2 Air Recirculation vs. Exhaust Design
Most air showers operate on a recirculation principle:
Air is filtered, discharged through nozzles, then returned and re-filtered
Minimizes energy consumption while maintaining cleanliness
In high-risk environments, partial exhaust designs may be used to further reduce contamination carryover.
4. Structural and Layout Considerations
4.1 Size and Capacity
Air shower dimensions should be determined based on:
Number of users per shift
Personnel flow rate
Cleanroom entry frequency
Common configurations include:
Single-person air showers
Double-person or tunnel-type air showers for high-traffic areas
4.2 Door Interlock Systems
To maintain pressure integrity and prevent cross-contamination:
Entry and exit doors must be electrically or mechanically interlocked
Only one door can open at a time during operation
Emergency release mechanisms should be included for safety
Interlock logic is a key engineering detail often reviewed during GMP audits.
5. Pressure and Integration with Cleanroom HVAC Systems
Air showers must be integrated into the overall cleanroom airflow and pressure control strategy:
Typically designed as a neutral or slightly positive pressure zone
Should not disrupt the cleanroom pressure cascade
Supply and return air volumes must be carefully balanced
Coordination between air shower design and the main HVAC system is essential to avoid pressure instability.
6. Control Systems and User Interface
Modern air showers are equipped with intelligent control systems, including:
Programmable cycle times
Visual and audible operation indicators
Touch panels or push-button interfaces
Optional access control integration
A clear, intuitive interface improves user compliance and operational efficiency.
7. Installation and Commissioning Considerations
Even the best design requires correct installation and validation:
Airtight installation to prevent bypass leakage
HEPA filter integrity testing (PAO/DOP test)
Air velocity and airflow pattern verification
Functional testing of door interlocks and controls
Commissioning data should be documented as part of the cleanroom qualification package.
8. Compliance with Standards and Regulations
Air shower design should align with relevant standards, including:
ISO 14644 (Cleanroom classification and operation)
GMP requirements for pharmaceutical and medical cleanrooms
Facility-specific biosafety or industry guidelines
Although air showers are not always explicitly mandated, they are widely recognized as best practice in controlled environments.
Conclusion
Air shower design is a multidisciplinary engineering task that combines airflow dynamics, filtration technology, structural design, and cleanroom integration. By focusing on key principles—effective airflow, proper filtration, reliable interlocking, and system integration—air showers can significantly enhance contamination control and cleanroom performance.
For cleanroom projects in pharmaceuticals, biotechnology, electronics, and animal research facilities, a properly engineered air shower is not just an accessory, but a critical element of a robust contamination control strategy.
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