Particulate classification: understanding ISO 5, ISO 7 and ISO 8 cleanroom classes
In controlled contamination environments, particle classification is a major benchmark for defining the level of air cleanliness. This classification is used to characterise the concentration of particles present in the air of a room and set a limit not to be exceeded. Air handling systems are then adapted accordingly. This classification is itself defined by the ISO 14644-1 standard, which establishes several cleanliness levels according to the number of particles per cubic metre of air.
It is important to understand that these classes do not merely describe a theoretical air quality; they directly govern the design of air treatment systems, the sizing of filtration equipment and the organisation of airflows within premises. In numerous sectors such as the pharmaceutical industry, biotechnology, healthcare or microelectronics, ISO 5, ISO 7 and ISO 8 classes are the most frequently encountered references.
Understanding particulate concentration thresholds
The ISO classification is based on the maximum number of airborne particles permitted per cubic metre of air, according to their size. The lower the ISO class number, the higher the particulate cleanliness requirements.
The dimensions 0.5 µm and 5 µm correspond to particle sizes expressed in micrometres (µm). As a guide, 1 µm corresponds to one thousandth of a millimetre. The standard sets, for each class, a maximum permissible concentration of particles whose size is equal to or greater than the dimension in question.
| Class | ≥ 0.5 µm | ≥ 5 µm |
|---|---|---|
| ISO 5 | 3,520 particles/m³ | 29 particles/m³ |
| ISO 7 | 352,000 particles/m³ | 2,930 particles/m³ |
| ISO 8 | 3,520,000 particles/m³ | 29,300 particles/m³ |
These values clearly show the gap between the different levels of cleanliness. For particles of 0.5 µm and larger, an ISO 5 class permits 100 times fewer particles than an ISO 7 and 1,000 times fewer than an ISO 8. The maximum concentrations given in the table come directly from the supplied NF EN ISO 14644-1.
However, please note:
The ISO classification characterises airborne particulate cleanliness. On its own, it provides no information on microbiological contamination or the nature of the particles present. The standard specifies that it does not characterise their physical, chemical, radiological or viable nature.
ISO 5 class for a highly controlled environment
ISO Class 5 corresponds to a very high level of particulate cleanliness. It may be required in areas that are particularly sensitive to contamination. It is found, for example, in aseptic filling areas, in certain pharmaceutical production steps or beneath workstations protected by laminar flow.
Depending on the application and the risk analysis, the use of a unidirectional airflow can help protect a critical zone and promote the removal of contaminants. High or very high efficiency filtration, potentially terminal, may be implemented depending on the desired performance and the specific requirements of the application. The air handling system must ensure a high degree of stability in flow rates and pressures.
At A2i, the design of solutions intended for ISO 5 environments is based on advanced expertise in air diffusion, filtration and differential pressures.
ISO 7 class for controlled environments
ISO Class 7 is one of the most common cleanliness levels in pharmaceutical facilities and laboratories. It is frequently encountered in various controlled environments, particularly in certain preparation, production or testing areas. However, the required level must be defined according to the activity, the process and the applicable risk analysis.
It is important to understand that the stability of the ISO 7 classification depends on the air handling system, but also on the organisation of personnel and material flows within the cleanroom.
ISO 8 class is a controlled cleanliness level
ISO 8 classification corresponds to a less demanding particulate cleanliness level than ISO 5 and ISO 7 classes. It can notably be found in certain peripheral areas of cleanrooms or in various production environments requiring the control of particulate contamination.
These spaces may include preparation, storage or circulation areas associated with cleanrooms. At A2i, air treatment solutions intended for ISO 8 environments are designed to ensure a balance between contamination control, operational reliability and energy performance.
Air handling at the heart of particulate classification
Maintaining an ISO class does not depend solely on the filters installed in the system. It relies on the coordination of all technical parameters, from the design of air treatment equipment to the organisation of airflows, including differential pressure management and thermal condition stability.
It is this comprehensive approach that helps maintain the expected performance of the cleanroom under its defined operating conditions. At A2I, the design of air handling equipment follows this exact logic: offering solutions tailored to controlled contamination environments and the performance levels defined for each project.
