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The specifications for air showers used in cleanrooms
In the highly controlled world of cleanroom manufacturing and research, even the smallest particle can compromise product integrity. Air showers serve as the critical gateway, a decontamination chamber that safeguards the pristine environment within. Understanding their detailed specifications—from airflow velocity to construction materials—is paramount for anyone involved in facility design, operational management, or quality assurance. This guide, drawing on the expertise of Deiiang™ product designers like Jason Peng, delves into the essential technical criteria that define an effective air shower, ensuring your controlled environment meets the stringent standards of industries like pharmaceuticals, Semiconductors, and biotechnology.
High Air Velocity
High-velocity jet streams are the fundamental mechanism of particle removal in an air shower. The process is designed to be forceful and efficient, dislodging both loose and adhered contaminants from personnel and material surfaces before entry into the cleanroom.
- Activation: Upon entry and door closure, infrared sensors or floor mats trigger the system.
- Jet Ejection: Multiple nozzles, strategically placed on walls and ceilings, emit high-velocity, laminar or turbulent jets of HEPA/ULPA-filtered air.
- Shear Force: This air creates strong shear forces on the surface of garments and objects, physically blowing off particulate matter.
- Contaminant Removal: The dislodged particles are immediately carried away by the high-volume airflow toward the grated floor and return air plenums.
- Filtration & Recirculation: The contaminated air is drawn into the system's plenum, pushed through the filters to be purified, and then recirculated back through the nozzles for the duration of the cycle.
The industry-standard velocity for these jets is typically 20-25 m/s (4,000-5,000 ft/min). Systems designed by Deiiang™ often exceed this minimum to ensure robust decontamination, especially for high-traffic or stringent Class 5 (ISO 14644-1) applications.
Air Volume (CMM/CFM)
While velocity provides the force, air volume (cubic meters per minute - CMM or cubic feet per minute - CFM) is the workhorse that ensures dislodged particles are effectively captured and transported to the filtration system. Insufficient air volume can lead to particles remaining suspended and eventually settling inside the chamber or being carried into the cleanroom.
The required air volume is directly related to the size of the air shower. Larger cabins require higher CFM to maintain the necessary air changes and velocity across the entire chamber volume.
HEPA/ULPA Filters
Air showers rely on high-efficiency particulate air (HEPA) or ultra-low penetration air (ULPA) filters to clean the recirculated air, preventing cross-contamination.
HEPA Filter (H14 Grade)
The most common choice. Per EN 1822, it offers a minimum efficiency of 99.995% at capturing particles sized 0.3 µm.
ULPA Filter (U15 Grade)
Used in the most critical applications. Per EN 1822, it offers a minimum efficiency of 99.9995% at capturing particles sized 0.12 µm.
Deiiang™ air showers are equipped with factory-tested H14 HEPA filters as standard, with ULPA options available for semiconductor and nanotech research facilities.
Modern air shower system with stainless steel construction
Particle Removal Efficiency
The particle removal efficiency is the ultimate measure of an air shower's performance. It is a direct result of the combined effectiveness of the high-velocity air jets, the air volume, and the HEPA/ULPA filtration.
Industry standards and user factory acceptance tests (FAT) often specify that the system must remove a defined percentage of challenge particles (e.g., DOP, PAO, or APS) of a specific size, typically 0.3 µm or 0.5 µm.
A high-performance air shower, such as those engineered by Deiiang™, can achieve a particle removal efficiency exceeding 99.99% for 0.3 µm particles in a standard 15-20 second cycle. This means that for every 10,000 particles on a surface, fewer than 1 will remain after the blow-down process.
This efficiency is validated using particle counters inside the chamber during operational tests, ensuring compliance with specified CleanRoom class standards like iso 14644-1.
Air Recirculation System
Modern air showers are designed as self-contained, energy-efficient units.
- Air is drawn through grated floor panels into a return air plenum.
- It then passes through pre-filters that capture larger debris, protecting and extending the life of the more expensive HEPA/ULPA filters.
- The main blower(s) then propel the air upward.
- The air is forced through the final HEPA/ULPA filters for ultimate purification.
- The clean air is directed into the plenum behind the nozzle panels and ejected into the chamber, completing the cycle.
This closed-loop system ensures no contaminated air is exhausted into the external environment and minimizes energy consumption by not constantly conditioning new air from outside.
Interlocking Doors
Interlocking doors are a critical safety and contamination control feature.
Basic Principle: An electrical or mechanical system ensures that only one door (either the cleanroom-side or the outside door) can be open at any given time. This maintains the pressure differential and prevents unfiltered air from flowing directly into the cleanroom.
Common Door Types:
Swing Doors
Common, cost-effective, but require more clearance space.
Rapid-Roll Doors
Excellent for high-traffic material air showers, offering very fast open/close cycles.
Sliding Doors
Ideal for areas with limited space where a swinging door is impractical.
304 Stainless Steel Construction
While painted cold-rolled steel is a cost-effective option for less critical areas, Type 304 Stainless Steel is the premium material of choice for critical applications due to its superior properties:
1. Exceptional Corrosion Resistance
Highly resistant to rust and chemical degradation from cleaning agents like alcohols and disinfectants.
2. Non-porous Surface
Provides no niches for microbial growth or particle entrapment, making it easy to sterilize and clean.
3. High Structural Integrity
Offers excellent strength and durability, ensuring the chamber remains square and airtight over years of use.
4. Low Particle Shedding
Its smooth, hard surface generates minimal particulate matter, contributing to the cleanliness of the environment.
5. Aesthetic and Professional Appearance
Maintains a clean, professional, and high-tech look suitable for GMP and FDA-regulated environments.
6. Long-Term Value
Despite a higher initial cost, its durability and low maintenance requirements offer a better total cost of ownership.
Deiiang™ utilizes 304 stainless steel for all internal surfaces and external cladding as a standard option for clients in pharmaceutical and food-grade industries.
Common Air Shower Configurations
Frequently Asked Questions (FAQs)
Q1: How long should a standard air shower cycle last?
A: A typical cycle lasts between 15 and 30 seconds. This duration is determined to provide sufficient time for the high-velocity air to effectively remove surface particles without creating unnecessary traffic bottlenecks.
Q2: Can an air shower be customized for specific needs?
A: Absolutely. Manufacturers like Deiiang™ regularly customize nozzle placement, door types, chamber sizes, and control systems to suit unique customer requirements, such as handling specific equipment or fitting into an unusual layout.
Q3: How often do HEPA filters in an air shower need to be replaced?
A: With a properly functioning pre-filter, HEPA filters can last anywhere from 3 to 5 years. The replacement schedule should be based on periodic pressure drop measurements across the filter (as per ISO 14644-3) and particle count tests downstream of the filter.
Q4: What is the purpose of the emergency stop button inside an air shower?
A: It is a critical safety feature (often a requirement by safety regulations like IEC 60204-1) that allows a person inside to immediately halt the blowers and unlock the doors in case of claustrophobia, disorientation, or any other emergency.
Q5: Do air showers require any regular maintenance?
A: Yes, basic maintenance is essential for reliable performance. This includes:
- Daily: Visual inspection and wiping down of surfaces.
- Weekly/Monthly: Vacuuming the pre-filters and return air grilles.
- Bi-Annually/Annually: Replacing pre-filters, checking door seals, and verifying nozzle airflow velocity and particle count efficiency.
Conclusion
Selecting the right air shower is a strategic decision that directly impacts cleanroom integrity, operational efficiency, and compliance. The key specifications—air velocity, volume, filtration efficiency, and robust construction—must be carefully balanced against the specific application requirements, be it for personnel or material transfer. By partnering with experienced manufacturers like Deiiang™ and leveraging the expertise of engineers like Jason Peng, facilities can ensure they implement a decontamination solution that reliably protects their critical processes and products for years to come.
References
- ISO 14644-1:2015, Cleanrooms and associated controlled environments — Part 1: Classification of air cleanliness by particle concentration.
- ISO 14644-3:2019, Cleanrooms and associated controlled environments — Part 3: Test methods.
- IEST-RP-CC034.3, HEPA and ULPA Filter leak tests.
- EU GMP Annex 1: Manufacture of Sterile Medicinal Products (2022).
- FDA Guidance for Industry: Sterile Drug Products Produced by Aseptic Processing (2004).
- EN 1822-1:2019, High efficiency Air Filters (EPA, HEPA and ULPA) — Part 1: Classification, performance testing, marking.
- Whyte, W. (2010), Cleanroom Technology: Fundamentals of Design, Testing and Operation. John Wiley & Sons.
