A cleanroom is a controlled environment that has low levels of pollutants such as dust, airborne microbes, aerosol particles, and chemical vapors. Cleanrooms are used extensively in manufacturing sectors like semiconductor, pharmaceutical, biotechnology, medical devices, aerospace etc. where ultra clean environment is required. Cleanrooms are rated based on the number and size of particles permitted per volume of air. This rating system is defined by the ISO 14644-1 standard.
ISO 14644-1 Cleanroom Classification
ISO 14644-1 is an international standard that was developed by the International Organization for Standardization (ISO) to classify and control cleanroom environments based on the quantity and size of airborne particles present. This standard establishes the cleanliness classifications from ISO Class 1 (very clean) to ISO Class 9 (least clean). Each subsequent ISO class allows for 10 times the number of 0.1 μm or larger particles per cubic meter of air compared to the previous class.
Here are the ISO 14644-1 cleanroom classifications:
| ISO Class | Maximum particles/m3 of air ≥0.1 μm | Maximum particles/m3 of air ≥0.2 μm | Maximum particles/m3 of air ≥0.3 μm | Maximum particles/m3 of air ≥0.5 μm | Maximum particles/m3 of air ≥1 μm |
|---|---|---|---|---|---|
| ISO Class 1 | 10 | 2 | N/A | N/A | N/A |
| ISO Class 2 | 100 | 24 | 10 | 4 | N/A |
| ISO Class 3 | 1,000 | 237 | 102 | 35 | 8 |
| ISO Class 4 | 10,000 | 2,370 | 1,020 | 352 | 83 |
| ISO Class 5 | 100,000 | 23,700 | 10,200 | 3,520 | 832 |
| ISO Class 6 | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 |
| ISO Class 7 | 352,000 | 83,200 | |||
| ISO Class 8 | 3,520,000 | 832,000 | |||
| ISO Class 9 | 35,200,000 | 8,320,000 |
As seen from the table, the ISO standard defines maximum concentration limits for particles of different sizes. The smaller the particle size, the cleaner the room has to be. This is because smaller particles can lead to defects in sensitive processes.
What is ISO Class 5 Cleanroom
ISO Class 5 is the cleanroom class that allows for a maximum concentration of 100,000 particles of 0.1 μm size per cubic meter of air. It also allows for a maximum of 23,700 particles of 0.2 μm size, 10,200 particles of 0.3 μm size, 3,520 particles of 0.5 μm size and 832 particles of 1 μm size per cubic meter of air.
ISO Class 5 cleanrooms have moderately controlled environments. Applications that use ISO Class 5 cleanrooms include pharmaceutical tablet coating, medical device assembly, tissue culture growth, etc. These environments require control of particulates to avoid defects, but ultra-low particle levels are not essential.
Some key facts about ISO Class 5 cleanrooms:
- ISO Class 5 environments allow 5 times more particles than ISO Class 4 and 5 times fewer particles than ISO Class 6.
- People are required to wear gloves, hairnet, beard mask, face mask and full body gowns in ISO Class 5 areas.
- Air supply should have at least EU5 grade filtration as per EN 1822 standard.
- The room should have suitable air changes per hour based on calculations.
- Room pressure should be positively pressurized compared to less clean adjacent areas.
- Entry to ISO Class 5 areas is through airlocks to maintain pressure differential.
- Activities that generate particles like use of powders should be avoided.
- Thorough cleaning protocols must be followed to control particles.
- Routine certification and monitoring of parameters should be implemented.
Typical ISO Class 5 Cleanroom Applications
Some common application areas that use ISO Class 5 cleanrooms include:
- Pharmaceutical manufacturing: Tablet coating, powder blending operations, small volume liquid filling.
- Medical devices: Medical electronics assembly, loaded PCB assembly, catheter production, blood filters.
- Healthcare: IV compounding aseptic preparations, cytotoxic drug preparations.
- Microelectronics: PCB assembly, optical goods assembly.
- Aerospace: Satellite assembly, aerospace electronics.
- Food industry: Additive manufacturing, dry ingredient handling.
- Biotechnology: Tissue culture growth, filtration operations.
ISO Class 5 cleanrooms offer moderate control of particulates for processes that need more cleanliness than ambient conditions but do not require ultra-low particle levels. Their applications strike a balance between cleanliness and cost.
Cleanroom Garments for ISO Class 5
Personnel entering ISO Class 5 cleanrooms are required to wear appropriate cleanroom garments. These specialized garments help minimize contamination from people. Here are the typical cleanroom garments worn in ISO Class 5 areas:
Coverall Garment
A full body coverall made of polypropylene or polyester is worn to cover street clothes. The fabric is usually white to show contamination easily. The coverall has elastic cuffs and collar for tight seal.
Shoe Covers
Shoe covers made of polypropylene are worn over regular shoes to prevent contamination from outside floors. Tacky pads may be used on bottom of shoes.
Head Covers
A hood or bouffant cap is worn to cover the head and hair. Beard masks are also required for facial hair.
Gloves
Latex or nitrile gloves are worn over the coverall sleeves. Finger cots may also be used during handling of sensitive items.
Face Mask
A surgical type face mask is worn to prevent release of facial particles. Some cleanrooms mandate full face shields.
Proper sealing of cuffs, collars and interfaces is crucial for effective containment. Garments are changed based on classified area cleanliness and operations performed.
Engineering Controls for ISO Class 5 Cleanrooms
Achieving ISO Class 5 air cleanliness levels for the defined particle sizes requires implementation of suitable engineering controls. Here are the key facets:
Air Filtration
Air supply must be filtered to remove particles. Filters used for ISO Class 5 areas should be minimum EU5 grade as per EN 1822 standard. This ensures removal of at least 95% of 0.4 μm particles. Installation of two filters in series achieves better filtration.
Air Changes
Sufficient air changes per hour are required to dilute particle concentration. 20 to 30 air changes per hour may be required for achieving ISO Class 5 levels based on calculations.
Airflow Patterns
Unidirectional airflow patterns like laminar or non unidirectional flow should be used. This avoids stagnant air zones and maintains air motion from clean to less clean areas.
Room Pressurization
Positive pressure differential of minimum +10 Pa between ISO Class 5 and adjacent lower grade areas should be maintained to avoid contamination ingress.
Air Showers and Air Locks
Air showers and airlocks between cleanroom zones utilize air filtration and pressure differentials to reduce particulate entry. Interlocking doors prevent cross contamination.
Proper engineering controls, well designed facilities and disciplined contamination control programs are must for consistent achievement of ISO Class 5 cleanliness.
Cleaning and Gowning Procedures
Strict gowning procedures and cleaning protocols must be implemented for ISO Class 5 operation. Key aspects include:
- Change room with donning procedures for wearing coverall, headgear, masks, gloves and shoe covers.
- Adhesive mats for tacky shoe covers.
- Sticky mats for removing excess particles before entry.
- Prep rooms with air showers between zones.
- Frequent surface cleaning inside cleanroom.
- Avoiding powder and lint generating activities.
- Vacuum cleaning instead of sweeping.
- Wiping instead of spraying disinfectants.
- Removal of waste from cleanroom after cleaning.
Personnel must be trained on maintaining discipline during material movement, cleaning and maintenance activities that can contaminate the cleanroom environment.
Monitoring ISO Class 5 Cleanrooms
Regular testing and monitoring is vital for ensuring that ISO Class 5 specifications are continually met. Critical parameters that need monitoring include:
- Airborne particulates: Counts of ≥0.1 μm, ≥0.2 μm, ≥0.3 μm, ≥0.5 μm and ≥1 μm particles per cubic meter of air using optical particle counters.
- Air pressure differential: Positive pressure difference between ISO Class 5 and lower grade rooms measured using differential pressure sensors.
- Airflow patterns: Using anemometers and smoke tests to verify unidirectional air motion.
- Air changes: Calculating ACH based on room size and airflow rate.
- Temperature and humidity: Maintaining desired temperature and RH levels.
- Air filter integrity: Testing for leaks and efficiency degradation.
Continuous monitoring systems with alarm capabilities may be deployed. Handheld instruments can also be used for spot checking. Re-certification audits must be conducted at periodic intervals against ISO 14644-1 standard.
Microbial Levels in ISO Class 5 Cleanrooms
While particulate levels are the primary metrics used to define cleanroom classes, microbial contamination also needs control. ISO Class 5 cleanrooms should meet the following microbial limits:
- Viable airborne particles: <100 CFU/m3
- Surface viable particles: <100 CFU/plate for floors and walls
- Surface viable particles: <10 CFU/plate for work surfaces
Routine microbiological sampling such as air impaction, surface swabs and contact plates should be performed. Fumigation and rigorous cleaning helps control microbial growth. Personnel must avoid processes that disseminatemicrobes.
Conclusion
ISO Class 5 is a moderately controlled cleanroom classification that allows for 100,000 particles of 0.1 μm size per cubic meter of air. Pharmaceutical, medical, aerospace and food product manufacturing utilize ISO Class 5 cleanrooms. These environments call for disciplined contamination control through proper garments, engineering controls, cleaning protocols and regular monitoring. Careful oversight and quality practices are essential for sustained ISO Class 5 conformance.