Cleanroom classification states the permitted concentration of airborne particles under defined conditions. It is a measurable performance requirement—not a complete design, a GMP grade or proof that a process is adequately controlled.
ISO 5 is cleaner than ISO 7, and ISO 7 is cleaner than ISO 8. The correct class must be justified against the process, contamination risk and applicable regulatory or customer requirements.
What does cleanroom classification mean?
ISO 14644-1 classifies air cleanliness by the concentration of airborne particles. The classification is established through particle-count testing at agreed particle sizes, sampling locations and occupancy conditions.
A lower ISO class number represents a more tightly controlled particle concentration. Reaching that condition depends on much more than installing filters. Air distribution, room fabric, pressure relationships, equipment, operations, cleaning, garments, access and maintenance all affect the outcome.
Classification also has boundaries. It does not by itself define viable microbiological limits, product protection, operator containment or the suitability of a room for a regulated activity. Those decisions need a wider process and risk assessment.
How ISO 5, ISO 7 and ISO 8 differ
| Class | Typical role in a facility | Questions that still need answering |
|---|---|---|
| ISO 5 | Critical or highly particle-sensitive work, sometimes as a localised zone rather than a whole room. | Is unidirectional airflow required? What is exposed, for how long, and under which operating state? |
| ISO 7 | Production, processing or background space for pharmaceutical, medical-device and precision work. | What pressure relationships, recovery performance, monitoring and cleaning controls support the process? |
| ISO 8 | Controlled manufacturing, preparation, transfer or support space where a less stringent particle limit is justified. | How are people and materials segregated, and which activities could challenge the room condition? |
What is an ISO 5 cleanroom?
ISO 5 is a highly controlled condition associated with critical or extremely particle-sensitive work. Depending on the application, it may be achieved across a full room or within a localised unidirectional-airflow zone, isolator or other critical workspace.
What is an ISO 7 cleanroom?
An ISO 7 cleanroom is commonly used for pharmaceutical, medical-device, laboratory and precision-manufacturing processes. It can be a background room or the primary processing environment, depending on the activity and regulatory context. Calling a room “ISO 7” does not specify its pressure regime, temperature, humidity, recovery time or microbiological controls.
What is an ISO 8 cleanroom?
ISO 8 provides controlled conditions for many manufacturing, preparation, support and transfer applications. Although less stringent than ISO 7 or ISO 5, it still requires coordinated design, commissioning and disciplined operation.
These examples are deliberately broad. The correct class cannot be selected from an industry label alone. A risk-led review should consider what the process is sensitive to, how product is exposed, the consequence of contamination and any regulatory or customer requirements.
As-built, at-rest and operational conditions
Classification needs an agreed occupancy state. “As built” considers the completed installation without production equipment. “At rest” considers installed equipment operating as agreed but without personnel carrying out the process. “Operational” considers the room performing its defined activity with the specified number of people present.
This distinction matters because people and processes are major sources of contamination. A room that performs well while empty may behave differently once operators move, doors open, equipment generates heat and materials enter the space.
How is cleanroom classification tested?
Classification testing uses a calibrated airborne particle counter and a documented sampling plan. The plan should identify the room, target class, occupancy state, particle sizes, sampling locations, equipment status and any relevant test conditions. Results need to be traceable to the room and test configuration so they can be reviewed and repeated.
Classification is only one part of verification. Depending on the facility, the evidence package may also include installed-filter leakage testing, airflow volume and velocity measurements, pressure-differential checks, recovery testing, airflow visualisation, temperature and humidity results, alarm checks and microbiological monitoring. Our guides explain how to compare cleanroom validation services and what to expect from HEPA filter validation.
ISO cleanroom classes and GMP grades are not interchangeable
ISO classification describes airborne particle cleanliness. For sterile medicinal manufacture, the EU GMP Annex 1 framework uses Grades A, B, C and D alongside contamination-control, environmental-monitoring and qualification expectations.
An ISO class should therefore not be converted mechanically into a GMP grade. The applicable grade, background environment and operating controls depend on the activity being performed and the contamination-control strategy. The same caution applies to healthcare, medical-device and specialist manufacturing requirements: classification is an input to the brief, not the whole brief.
What classification changes in the design
The target condition informs filtration, airflow, air-change strategy, pressure control, recovery and monitoring, but those elements must be designed together. Higher airflow is not automatically better. The system must account for heat loads, process emissions, room geometry, noise, energy, access and the ability to maintain equipment safely.
Room fabric also matters. Surfaces should suit the cleaning regime and process, with junctions, penetrations, doors, glazing and services detailed to limit particle traps and leakage. Personnel and material routes should reduce unnecessary crossing and support the intended contamination-control approach.
The classification strategy should be carried into the cleanroom design and build brief, then verified at the agreed project stages. Where speed, future alteration or reduced site disruption matters, it can also inform selection of a modular cleanroom system.
Five questions to answer before requesting a proposal
- What happens in the room? Describe the process, product exposure, equipment and number of operators.
- What must be protected? Product, patient, operator, environment—or a combination?
- What requirement drives control? A regulation, standard, customer specification, internal quality decision or sensitive process?
- Which occupancy state matters? Define when and how performance must be demonstrated.
- What are the practical constraints? Location, existing building, services, programme, budget, access and future expansion.
A good cleanroom partner will test the assumptions behind the class, not simply price a room around a label. If the answers are not yet complete, that is a valid reason to begin with feasibility and concept design.
Common classification questions
Is ISO 7 always required for medical-device manufacturing?
No. The required environment should follow the device, manufacturing step, exposure, contamination risks and the manufacturer’s quality and risk-management processes. The medical-device cleanroom requirements guide explains the decisions that belong in that assessment.
Does an ISO classification certificate mean the room is compliant?
It confirms the reported classification result under the stated test conditions. It does not by itself demonstrate that every regulatory, process, microbiological, monitoring or occupational-safety requirement has been met.
How often should a cleanroom be reclassified?
The interval depends on the applicable standard, regulatory framework, monitoring strategy, risk and change history. Reclassification may also be needed after significant maintenance, alterations or a change that could affect the qualified state.
Turn the requirement into a useful brief.
Share the process, intended classification, occupancy state and evidence requirements you know today. Cleanrooms Direct will review the scope and match it with suitable UK cleanroom expertise.
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