A Class 5 cleanroom has strict requirements for air cleanliness, temperature, humidity, pressure, personnel and gowning, and more. Achieving and maintaining Class 5 cleanroom standards ensures the environment is optimized for sensitive processes that cannot tolerate contamination.
What is a Class 5 Cleanroom?
Cleanrooms are controlled environments with low levels of particulates, like dust or microbes. They are rated by class, with Class 1 cleanrooms having the highest levels of air purity. Class 5 cleanrooms, while not as strict as Class 1-3 standards, still maintain a high level of cleanliness and control.
Class 5 cleanrooms have no more than 3,520 particles of 0.5 microns or larger per cubic meter of air. For reference, a single particle of human skin or a speck of dust is around 30-40 microns in size. Class 5 standards mean the cleanroom air has less than 1 particle per 11.5 cubic feet.
Air Cleanliness
The air purity of a Class 5 cleanroom is maintained through the use of high-efficiency particulate air (HEPA) filters. All air entering the cleanroom space passes through HEPA filters that capture 99.97% of all particles 0.3 microns and larger.
In addition to filtering incoming air, Class 5 cleanrooms use positive pressure to keep contaminated air out. The cleanroom is supplied with filtered air at a rate that creates consistent positive pressure. Air moves from areas of high pressure to low pressure. So if a cleanroom has higher pressure than surrounding spaces, air will move outward rather than letting unfiltered air move in.
To achieve Class 5 air cleanliness, a minimum of 20 air changes per hour are required. However, guidelines recommend 30-45 air changes per hour for maintaining consistent particle counts below 3,520 particles/m3. Facilities may opt for even higher air change rates in critical spaces.
Airflow Design
Proper airflow is essential for Class 5 cleanrooms. Air should flow in a unidirectional, vertical laminar pattern from the ceiling to the floor. This prevents particles from migrating on horizontal air currents.
Turbulent, non-unidirectional airflow can allow “dead zones” where contaminants build up. Facility designers should strategically place diffusers, returns, and barriers to guide smooth vertical airflow through the entire cleanroom.
Temperature and Humidity
Consistent temperature and humidity levels prevent fluctuations that could disrupt delicate processes. Class 5 cleanrooms must adhere to the following standards:
- Temperature: 22°C ± 3°C
- Humidity: 45% ± 5% RH
The optimal temperature and humidity settings may vary based on the specific processes, materials, or equipment in the cleanroom. But any chosen setpoints must be maintained within tight margins of ±3°C and ±5% RH.
Temperature and Humidity Control Strategies
Class 5 cleanrooms use a combination of heating, air conditioning, humidification, and/or dehumidification to achieve proper temperature and humidity standards. This environmental control equipment should distribute air evenly and prevent hot or cold spots.
Separate temperature and humidity sensors are strategically located to identify fluctuations. A building automation system monitors sensor readings and adjusts equipment as needed to maintain setpoints.
Pressure
As mentioned for air cleanliness, Class 5 cleanrooms use positive pressure. Guidelines recommend a minimum pressure differential of 2.5 Pascals between the cleanroom and surrounding spaces.
Maintaining this constant positive differential minimizes the risk of contaminants infiltrating the cleanroom. Doors, windows, vents, and any other openings are designed to avoid disrupting pressure differentials when opened.
Monitoring Pressure
Sensors continuously monitor the pressure differentials between the Class 5 cleanroom and adjacent spaces. Pressure is displayed visually for personnel inside the cleanroom. Audible alarms activate if differentials fall outside the recommended 2.5 Pascal minimum.
Personnel and Gowning Requirements
People are a major source of particles and microbes that can contaminate cleanroom environments. Class 5 cleanrooms establish strict gowning and personnel behavior requirements.
Garments
All people entering a Class 5 cleanroom must wear full coveralls, hoods, boots, gloves, masks, and goggles. Garments are made of special non-shedding materials designed to minimize particle generation.
Workers must undergo gowning procedures in an adjacent staging room. Gowns are put on in a specific sequence and taped securely to minimize skin exposure.
Entry and Exit Protocols
Transitions in and out of the cleanroom follow strict routines to avoid infiltration. Workers pass through an airlock space, ensuring only one door is open at a time. Upon exiting, they undergo de-gowning procedures to remove garments in a controlled manner.
Some facilities may also have showers or air showers to remove particulates before re-entering. Limiting traffic and unnecessary movement helps maintain Class 5 conditions.
In-Process Protocols
Within the cleanroom, personnel must follow protocols to minimize any contaminants they may bring inside. Moving slowly and deliberately avoids stirring up particles. Activities like running or talking loudly are prohibited.
Other guidelines include:
- No cosmetics, perfumes, or scented products
- No jewelry or watches
- Covered hair and beards
- Cleanroom shoes must not be worn outside the clean space
By adhering to all entry, exit, and in-process protocols, personnel help preserve the Class 5 clean environment.
Facility Design and Materials
The design, layout, and materials used in a Class 5 cleanroom aim to minimize contamination risks. Guidelines to follow include:
- Logical workflow from “dirty” to “clean” areas
- Smooth nonporous surfaces for easy cleaning
- Minimal features and furnishings
- Strategic seam and joint locations
- Separate zones for support functions like storage or offices
Cleanrooms may use materials like vinyl, epoxy-coated panels, or stainless steel. Smooth finishes and minimal joints make surfaces easier to sterilize between uses.
Facility Certification
Once constructed, cleanrooms undergo certification to validate Class 5 particle count and airflow standards. Baseline particle counts are measured in an “as-built” condition. Filters are then run for 72 hours with simulated maximum personnel activity.
With the cleanroom operating at full capacity, particle counts are measured on a grid pattern. Airflow, pressurization, and filter function are also validated. The cleanroom must maintain Class 5 levels throughout certification to be approved for use.
Cleaning and Disinfection
Even in operation, Class 5 cleanrooms require extensive cleaning. Surfaces are disinfected frequently to eliminate microbial contaminants. Typical practices include:
- Daily/weekly surface cleaning of walls, floors, furnishings
- Disinfectant “fogging” or air filtration after each shift
- Routine cleaning of filters, fan units, vents
- Monthly deep cleaning during maintenance closures
Cleaning methods avoid stirring up excess particles. Disinfectants used inside the cleanroom must be compatible with the processes and materials handled.
Monitoring and Testing
To ensure standards are maintained, particle counts and microbial samples are tested regularly. Surfaces may be tested for residual organic matter. Any spikes could prompt additional cleaning.
Air sampling also verifies that particle and microbial levels remain within Class 5 specifications after cleaning.
Documentation and GMP
Documentation provides proof that Class 5 cleanroom requirements are consistently met. Facilities follow Good Manufacturing Practices (GMP) to document proper operations.
SOPs
Detailed standard operating procedures (SOPs) provide step-by-step instructions for gowning, entry/exit, cleaning, testing, and all other protocols. Personnel must follow SOPs exactly.
Logbooks
Logs are maintained to record activities, testing results, deviations, and corrective actions. Airflow, differential pressure, temperature and humidity are typically logged around the clock.
Alarms
Alarm events, power outages, or any disruptions in the cleanroom are recorded and investigated. The cause of the issue and the actions taken to address it are documented.
Certifications and Audit Records
Initial cleanroom certification reports validate the Class 5 design standards. Re-certifications every 6-12 months verify ongoing compliance. Internal and third-party audits review overall GMP adherence.
By maintaining proper documentation, facilities can prove the cleanroom consistently meets all Class 5 requirements.
Conclusion
Class 5 cleanrooms allow sensitive industrial and scientific processes to proceed in extremely controlled environments. By filtering air, controlling airflow, limiting particles, restricting personnel, and extensive cleaning, Class 5 cleanrooms minimize risks of contamination.
Achieving a consistent particle count below 3,520/m3 and maintaining positive pressure differentials provides optimal conditions. Strict protocols for entry, exit, behaviors, gowning, materials, and design also support Class 5 standards.
With vigilance in upholding all these requirements, Class 5 cleanrooms create pristine spaces for critical operations vulnerable to infinitesimal levels of particles or microbes.