ISO Class 5, 7 and 8 Cleanrooms Explained
Understand airborne particle limits, typical pharmaceutical applications, classification states, and how ISO classes relate to GMP cleanroom grades.
ISO Class 5, 7, and 8 cleanrooms are common classifications discussed in pharmaceutical facility design and qualification. The number refers to a defined level of airborne particulate cleanliness: a lower ISO class number represents a cleaner air classification. To use these labels correctly, teams must know the particle-size threshold, room state, sampling method, and intended manufacturing activity.
This guide explains the difference between ISO Class 5, 7, and 8 cleanrooms, shows common particle concentration limits, and describes how these classes fit into pharmaceutical manufacturing. It also clarifies a frequent source of confusion: an ISO class is not automatically the same as a GMP grade. Cleanroom design must be supported by a risk-based cGMP strategy and qualified environmental controls.
What does an ISO cleanroom class mean?
ISO 14644-1 classifies air cleanliness by the concentration of airborne particles at specified threshold sizes. A particle counter samples a measured volume of air and counts particles equal to or larger than the selected size. The classification is assigned by comparing results from defined locations with the applicable concentration limits.
The class number is logarithmic. As the class number increases, the maximum permitted particle concentration increases. Therefore, ISO Class 5 is cleaner than ISO Class 7, and ISO Class 7 is cleaner than ISO Class 8.
ISO Class 5, 7 and 8 particle limits
The following values show maximum concentrations per cubic metre at commonly used particle thresholds. Confirm all limits against the controlled copy of the current ISO standard and the classification protocol before applying them to a facility.
| ISO class | Maximum concentration ≥0.5 µm | Maximum concentration ≥5.0 µm | Relative cleanliness |
|---|---|---|---|
| ISO Class 5 | 3,520 particles/m³ | 29 particles/m³ | Highest cleanliness among these three classes |
| ISO Class 7 | 352,000 particles/m³ | 2,930 particles/m³ | Intermediate cleanliness |
| ISO Class 8 | 3,520,000 particles/m³ | 29,300 particles/m³ | Least stringent of these three classes |
These are concentration limits for classification, not particle counts expected in every routine sample regardless of volume. Results must be expressed and compared using the specified sample volume and measurement approach. ISO 14644-1 covers classification by airborne particle concentration within its stated particle-size scope; it does not identify particle composition or determine whether a particle is viable.
ISO Class 5 cleanrooms
ISO Class 5 has the tightest particle limit of the three classes discussed here. In pharmaceutical sterile manufacturing, it is often relevant to critical zones where sterile product, container closures, or sterilized product-contact surfaces are exposed. Examples may include a filling zone protected by unidirectional airflow, an isolator workspace, or a critical work zone in a suitable barrier system.
The label “ISO 5” alone does not establish that the operation is suitable for aseptic processing. The design and qualification must also consider airflow protection, interventions, equipment layout, cleaning and disinfection, personnel practices, viable monitoring, and contamination-control strategy.
ISO Class 7 cleanrooms
ISO Class 7 is less stringent than ISO Class 5 but substantially cleaner than ISO Class 8. It may be selected for controlled backgrounds, support rooms, or manufacturing steps where the product and process risk justify that level. In sterile facilities, a room may serve as a background to a higher-grade critical area, but the applicable GMP grade and process design must be evaluated separately.
For non-sterile operations, ISO Class 7 may be considered for exposed materials or processes that require enhanced particulate control. The actual target should be derived from product risk, process capability, equipment, personnel, and facility design rather than copied from another plant.
ISO Class 8 cleanrooms
ISO Class 8 is the least stringent of these three classes while still representing a controlled environment. It may be used in support or preparation areas, material staging, or selected non-sterile manufacturing operations when the process risk assessment supports it.
An ISO Class 8 designation does not mean that a room is “uncontrolled.” It still requires appropriate facility design, cleaning, personnel practices, HVAC performance, and a monitoring program suited to its use.
Comparison at a glance
| Feature | ISO Class 5 | ISO Class 7 | ISO Class 8 |
|---|---|---|---|
| Particle control | Very stringent | Stringent controlled environment | Controlled environment with broader particle allowance |
| Example use context | Critical exposed-product work zone, where designed and qualified | Selected background or process support areas | Selected support, staging, or non-sterile operations |
| Pharmaceutical meaning | Does not automatically equal GMP Grade A | Does not automatically equal GMP Grade B or C | Does not automatically equal GMP Grade C or D |
| Other controls still needed | Viable monitoring where applicable, HVAC qualification, pressure control, airflow assessment, cleaning, gowning, and process-specific controls | ||
ISO class versus pharmaceutical GMP grade
ISO classes and pharmaceutical GMP grades address related but distinct requirements. ISO classification is based on airborne particle concentration at specified sizes and locations. GMP grades add manufacturing context, such as intended use, room state, aseptic risk, and environmental monitoring expectations.
For example, an ISO Class 5 particle result does not alone demonstrate that a critical aseptic zone is controlled. FDA notes that ISO 14644 classifications are useful for non-viable particle cleanliness, but sterile drug manufacturers should not rely on ISO classification alone when qualifying a facility because microbiological and operational controls also matter. genui{"citation":{"ref":"turn181search1"}}
At-rest and operational classification states
A cleanroom classification is meaningful only when the room state is stated. Qualification protocols commonly define:
- At rest: the room is complete, HVAC is operating as specified, and no personnel are present.
- In operation: the room is functioning in a defined production configuration with specified personnel, equipment, and activities present.
Particle levels can rise during operation because personnel, materials, and equipment generate or resuspend particles. A facility should define how the room is configured for each test state and ensure the test reflects intended use.
How cleanroom classification is performed
1. Define the classification plan
Identify the room boundaries, ISO target, particle sizes, state, sampling locations, acceptance criteria, instrument, sample volumes, and data-evaluation approach. The protocol should identify the applicable standard edition and any additional GMP requirements.
2. Select a suitable particle counter
Use a calibrated optical particle counter with appropriate size channels and sampling flow. Verify the instrument’s calibration status, sampling probe, tubing, data output, and operational checks. Particle counters measure optical particle size and concentration; they do not identify composition.
3. Select representative locations
Use the location-selection method required by the classification standard, then assess whether additional points are needed to cover critical operations or likely risk locations. Consider room geometry, air supply and return, work height, equipment, doors, and exposed product positions.
4. Sample in the defined state
At every point, collect the required sample volume at the specified flow and record the room state and activity. Keep the probe position and sampling sequence consistent. During operational testing, avoid disrupting the activity being assessed.
5. Evaluate results and report the conclusion
Compare each required location and particle-size result with the pre-approved criteria. Apply any required statistical evaluation exactly as specified by the standard. Document invalid samples, deviations, retests, and the basis for the final classification decision.
What ISO class does a pharmaceutical cleanroom need?
There is no single ISO class that applies to every pharmaceutical room. The appropriate classification depends on the product, whether it is sterile, the process step, the degree of product exposure, contamination hazards, equipment design, and applicable regulatory requirements.
Document the rationale in the facility design basis, contamination control strategy, or qualification plan. Link the room classification to the HVAC validation program and its ongoing monitoring controls.
Qualification and ongoing monitoring
Initial classification is one part of room qualification. A complete pharmaceutical cleanroom qualification may also evaluate installed HEPA filters, airflow volume or velocity, pressure differentials, airflow visualization, recovery, temperature, humidity, and other room-specific attributes. The exact test set should follow the intended use and risk assessment.
After initial qualification, routine monitoring and periodic requalification help demonstrate continued control. Establish alert and action levels, sampling frequency, review responsibilities, and responses to trends or excursions. Changes to room layout, HVAC settings, equipment, process, or classification should be assessed through change control and may trigger partial or full requalification.
Qualification documentation should be controlled within the site quality system. Requirements and test evidence may connect to DQ, IQ, OQ, and PQ.
Common errors when using ISO Class 5, 7 and 8 labels
- Treating an ISO class as an automatic GMP grade equivalence.
- Reporting particle counts without stating size thresholds, room state, and units.
- Using a clean at-rest result to claim control during actual operations.
- Assuming non-viable particle counts provide evidence of microbial control.
- Selecting a class because it is common in another facility rather than performing a risk-based assessment.
- Ignoring localized contamination risks because the overall room classification passes.
- Using a particle counter with overdue calibration or inadequate sampling configuration.
- Failing to investigate recurring alert-level trends because individual samples remain below the action limit.
Key takeaways
- ISO Class 5 is cleaner than ISO Class 7, which is cleaner than ISO Class 8.
- At ≥0.5 µm, the respective concentration limits are 3,520, 352,000, and 3,520,000 particles/m³.
- ISO 14644-1 classifies airborne particle concentration; it does not characterize viable microorganisms or particle composition.
- ISO class and GMP grade are not interchangeable without checking the specific requirements.
- Room classification must state the particle sizes, sample locations, room state, and acceptance criteria.
- Cleanroom suitability requires a broader qualification and monitoring program tailored to process risk.
Conclusion
ISO Class 5, 7, and 8 cleanrooms represent different levels of airborne particulate cleanliness, with ISO Class 5 imposing the strictest limits among the three. Pharmaceutical teams should use these classifications as one part of facility control—not as a complete statement of GMP compliance. Select the appropriate class through a documented risk-based assessment, qualify the room in defined states, and maintain control through monitoring, HVAC qualification, and change management.
Frequently asked questions
1. What is the difference between ISO Class 5, 7 and 8?
The classes differ in the maximum airborne particle concentrations permitted. ISO Class 5 is the cleanest of the three; ISO Class 8 permits the highest concentration.
2. What is the ISO Class 5 particle limit at 0.5 microns?
The maximum concentration for ISO Class 5 at ≥0.5 µm is 3,520 particles per cubic metre under the ISO classification table.
3. What is the particle limit for ISO Class 7?
At ≥0.5 µm, ISO Class 7 allows up to 352,000 particles/m³. At ≥5.0 µm, the commonly listed maximum is 2,930 particles/m³.
4. What is the particle limit for ISO Class 8?
At ≥0.5 µm, ISO Class 8 allows up to 3,520,000 particles/m³. At ≥5.0 µm, the commonly listed maximum is 29,300 particles/m³.
5. Is ISO Class 5 the same as GMP Grade A?
No. ISO Class 5 and GMP Grade A are not automatically equivalent. GMP grades include pharmaceutical context and additional requirements such as room state and contamination-control measures.
6. Is ISO Class 7 suitable for pharmaceutical manufacturing?
It may be suitable for some process or background areas when supported by a documented risk assessment and applicable GMP requirements. Suitability depends on the process and product, not the class label alone.
7. Does an ISO cleanroom class control microorganisms?
No. ISO particle classification measures non-viable airborne particle concentration. Microbiological control requires separate viable monitoring and contamination-control measures.
8. What is the difference between at-rest and in-operation classification?
At-rest testing is performed without personnel present in a completed, operating room. In-operation testing is performed with defined personnel, equipment, and activities present.
9. How often should an ISO cleanroom be reclassified?
Follow the applicable standard, GMP expectations, and approved site procedure. Frequency should also consider room risk, prior performance, changes, and monitoring trends.
10. Can ISO Class 8 be used for sterile manufacturing?
Some support spaces may be classified at ISO Class 8 depending on their function, but critical sterile operations have specific GMP requirements. Determine room grade and class from the process design and current applicable regulations.
- ISO 14644-1:2015 — Cleanrooms and associated controlled environments: Classification of air cleanliness by particle concentration
- U.S. FDA — Questions and Answers on CGMP: Production and Process Controls
- U.S. FDA — Sterile Drug Products Produced by Aseptic Processing: Current Good Manufacturing Practice
- European Commission — EudraLex Volume 4, EU Guidelines for Good Manufacturing Practice
Educational content only. Confirm the current standard edition, regulatory annex, and approved site procedures before using classification limits in a GMP protocol.
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