Cleanroom classes explained:
ISO 5, ISO 7 and ISO 8.

“What class does the cleanroom need to be?” is often the first technical question in a project. It is important—but it is not enough to define a safe, compliant or buildable facility.

What does cleanroom classification mean?

Cleanroom classification is a way of describing air cleanliness by the concentration of airborne particles under defined test conditions. The ISO 14644 family is widely used to provide a common classification framework for cleanrooms and associated controlled environments.

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.

How ISO 5, ISO 7 and ISO 8 are commonly used

ISO 5

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.

ISO 7

ISO 7 is common across pharmaceutical, medical-device, laboratory and precision-manufacturing environments. It can be used as a background or primary processing area depending on the process and regulatory context.

ISO 8

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.

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.

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.

For GMP or other regulated projects, classification sits inside a wider quality and contamination-control framework. Grades, microbial monitoring, qualification and process-specific expectations should be interpreted by competent specialists.

Five questions to answer before requesting a proposal

1. What happens in the room? Describe the process, product exposure, equipment and number of operators.
2. What must be protected? Product, patient, operator, environment—or a combination?
3. What requirement drives control? A regulation, standard, customer specification, internal quality decision or sensitive process?
4. Which occupancy state matters? Define when and how performance must be demonstrated.
5. 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.