ISO 14644-1 defines what a cleanroom class means by setting particle concentration limits, while ISO 14644-2 sets the monitoring and retesting evidence that keeps that class credible. Part 1 gives you a number, and part 2 tells you how often and how you prove you still hold it. Reading them as one document is what auditors expect, and treating a single classification test as ongoing monitoring is the gap they most often record.
What does ISO 14644-1 actually classify?
Part 1 is the classification standard. It defines ISO Classes 1 to 9 by the maximum permitted concentration of particles at sizes from 0.1 µm to 5 µm, using a formula that converts a class number into a limit for a chosen particle size.
At ISO Class 5 the limit for particles of 0.5 µm or larger is 3,520 per cubic metre, and each step up in class allows ten times more particles. Classification answers a single question: does this space meet the limits for the class you claim?
What does ISO 14644-2 add?
Part 2 adds the evidence. It describes how you demonstrate that a cleanroom continues to perform as classified, including the monitoring plan, the tests you run and the maximum interval between them.
It does not set the particle limits, and it does not choose your sampling points for you. In practice part 2 is where you write down what you will monitor, how often, and what you will do when a result drifts toward the limit.
A monitoring plan that samples too few locations, or that ignores the hours when the room is busiest, produces numbers that look reassuring and prove very little. The plan has to be able to fail, or it is not a test.
How often must a cleanroom be retested?
Retesting is a scheduled event, not a one-off. Under the interval logic described in ISO 14644-2, spaces at or below ISO Class 5 are commonly retested every six months, and higher classes on a twelve-month interval; confirm the current figures against the standard itself.
The interval is a maximum, not a target. A risk assessment, a change to the room or a failed result can all bring the next test forward.
A higher-class interval also does not excuse you from routine particle checks in the areas where product is exposed, or from acting on a trend that is moving toward the limit between formal tests.
Which part covers the test methods?
The test methods themselves sit in ISO 14644-3, which describes how to measure particle counts, air changes, filter integrity and recovery. Part 1 gives the limit, part 2 sets the schedule, and part 3 explains how to perform the measurement so that the numbers are comparable.
When a supplier or a contractor cites ISO 14644, ask which part they mean, because the answer changes what they are actually offering.
What consumables do cleanroom auditors ask about?
Auditors follow the people and the supplies into the room, because equipment and personnel are the main sources of particles. That makes low-shedding consumables part of the monitoring plan rather than a housekeeping detail.
The lines that come up are non-woven shoe covers for gowning and bouffant caps for head covering, alongside wipes that do not leave fibres behind. The question is rarely whether you have them; it is whether gowning and cleaning procedures show when they are used and changed.
Keeping gowning supplies at the entrance to the controlled area, with a written change frequency, is what turns a procedure into a habit that a reviewer can follow.
The common ISO 14644-1 classes, their particle limits and the retest expectation under part 2 are set out below.
| ISO Class | Limit for particles ≥0.5 µm (per m³) | Typical use | Re-test expectation under ISO 14644-2 |
|---|---|---|---|
| ISO Class 5 | 3,520 | Direct compounding area, laminar bench | Six months for classes at or below ISO 5 |
| ISO Class 6 | 35,200 | Cleanroom zones around critical operations | Twelve months under the higher-class interval |
| ISO Class 7 | 352,000 | Buffer room for sterile compounding | Twelve months |
| ISO Class 8 | 3,520,000 | Ante-area and general clean manufacturing | Twelve months |
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Frequently Asked Questions
Is ISO 14644-1 the same as the old US Federal Standard 209E?
No, and the classes do not map exactly. ISO 14644-1 uses logarithmic ISO classes that refer to particles per cubic metre; the older Federal Standard used imperial class names such as Class 100. Legacy documents still cite the old names, which is a common source of specification mismatches.
Does ISO 14644-1 require continuous monitoring?
No. Part 1 defines classification, which is a periodic test against limits. Whether you monitor continuously or intermittently is a monitoring-plan decision that belongs to part 2 and to your own risk assessment, especially for areas where the product is exposed.
Which ISO classes match sterile compounding rooms?
The direct compounding area is ISO Class 5. The rooms around it are commonly specified as ISO Class 7 and ISO Class 8 depending on layout and category. That mapping comes from the compounding chapter, not from ISO 14644 itself.
Can a portable particle counter be used for classification?
Yes, provided the sampling plan, sample volume and number of locations satisfy the standard and the counter is calibrated. The finding that shows up in audits is not the instrument; it is a plan that samples too few locations to be representative.
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