What is ISO 14644-1:2015?
ISO 14644-1:2015 is the international standard used to classify the cleanliness of air in cleanrooms and clean zones according to the concentration of airborne particles. It establishes ISO Classes 1 through 9, with lower class numbers representing stricter limits and cleaner environments.
The classification is determined by measuring the number of airborne particles equal to or larger than selected particle sizes at defined sampling locations. According to the official ISO 14644-1:2015 publication, classification covers threshold particle sizes from 0.1 µm to 5 µm and is based on measurements made with light scattering airborne particle counters.
What does ISO 14644-1:2015 classify?
The standard classifies air cleanliness by the concentration of suspended particles within a cleanroom, clean zone or certain separative devices. Its purpose is to provide a consistent method for determining whether an environment meets a specified ISO cleanliness class.
ISO 14644-1 focuses on particle concentration in the air. It does not determine whether particles are viable microorganisms, toxic substances, radioactive materials or chemically reactive contaminants. These risks may require additional microbiological, chemical or occupational monitoring.
What are ISO cleanroom classes?
ISO 14644-1 defines nine cleanliness classes. ISO Class 1 has the strictest particle concentration limits, while ISO Class 9 permits higher concentrations. A complete classification must identify the ISO class, the occupancy state and the particle sizes considered.
- ISO Classes 1 to 3: extremely controlled environments used in highly contamination-sensitive processes.
- ISO Classes 4 and 5: high-cleanliness environments frequently associated with aseptic processing, microelectronics and critical operations.
- ISO Classes 6 to 8: controlled production, preparation, packaging and support areas.
- ISO Class 9: the least restrictive class within the ISO 14644-1 classification system.
The correct class depends on the process, product sensitivity, regulatory requirements and contamination risks. ISO 14644-1 does not prescribe one universal class for every pharmaceutical, laboratory or industrial application.
Particle sizes considered by the standard
Classification may use one or more threshold particle sizes between 0.1 µm and 5 µm. The result expresses the maximum permitted concentration of particles equal to or larger than the selected size per cubic metre of air.
Particles smaller than 0.1 µm are treated separately as nanoscale or ultrafine particles. Particles larger than 5 µm may require an additional macroparticle descriptor. These populations are not covered by the conventional ISO class calculation in the same way as the main classification range.
How is a cleanroom classified?
Classification begins by defining the room or zone, the target ISO class, the occupancy state and the particle sizes to be measured. A sampling plan is then established based on the area of the environment and the requirements of the standard.
- Define the cleanroom boundaries and classification objective.
- Select the target ISO class and relevant particle sizes.
- Identify the occupancy state for the test.
- Determine the number and location of sampling points.
- Use a calibrated light scattering airborne particle counter.
- Collect the required air volume at each location.
- Compare the measured concentrations with the class limits.
- Document the test conditions, equipment, locations and results.
Classification should be conducted using calibrated equipment and technically justified sampling procedures. The ISO 14644-3:2019 provides complementary test methods for cleanrooms and associated controlled environments.
Occupancy states
A cleanroom may be classified in the as-built, at-rest or operational state. The selected state can significantly affect particle counts because people, equipment and active processes are important contamination sources. The classification report must clearly state the condition in which testing was performed.
Classification and monitoring are not the same
ISO 14644-1 establishes how the room is classified at a defined point in time. Routine monitoring is addressed by ISO 14644-2:2015, which supports the development of a monitoring plan to provide evidence that air cleanliness performance is maintained.
A room that passed its initial classification can later experience contamination caused by filter failure, inadequate cleaning, poor gowning, excessive occupancy, maintenance activities or changes in airflow. For this reason, classification should be supported by monitoring, maintenance, investigation of deviations and periodic reassessment.
Where is ISO 14644-1 applied?
The standard is used in sectors where airborne particles can compromise product quality, research integrity, manufacturing yield or patient safety. Common applications include:
- Pharmaceutical and biopharmaceutical manufacturing.
- Medical device production.
- Hospitals and aseptic preparation areas.
- Semiconductor and microelectronics manufacturing.
- Aerospace and precision engineering.
- Biotechnology, cell culture and research laboratories.
- Optics, photonics and advanced materials.
- Food, cosmetics and other controlled production processes.
Does ISO 14644-1 certify a cleanroom?
ISO publishes the classification requirements but does not inspect facilities or issue cleanroom certificates. Testing and classification may be performed internally or by a qualified third party, depending on contractual, regulatory and quality requirements.
A test report should not be interpreted as permanent assurance that the room will remain within the class. It documents performance under the stated conditions and at the time of testing.
Is ISO 14644-1:2015 still current?
Yes. ISO 14644-1:2015 is the second edition of the standard and replaced ISO 14644-1:1999. It was reviewed and confirmed by ISO in 2021 and remains current. The official ISO catalogue currently identifies it as a published standard under systematic review, which does not mean that it has been withdrawn or replaced.