Cleanroom Qualification Tests: What ISO 14644-3 Covers and in What Order

Three standards, three jobs

Standard	What it does
ISO 14644-1	Classifies air cleanliness by particle concentration — the ISO class.
ISO 14644-2	Sets how the room is monitored to show it stays in its class, and the maximum time between classifications.
ISO 14644-3	Describes the test methods: airflow, filter leak, pressure, visualisation, recovery, temperature, humidity and others.

In a GMP facility the same tests sit inside the qualification lifecycle: design qualification of the HVAC and room layout, installation qualification of what was built, operational qualification of how it performs, and performance qualification in normal use. EU GMP Annex 1 expects cleanrooms to be qualified and requalified, with the tests and acceptance criteria justified by risk.

The test set

Test	What it proves	Typical state
Airflow volume or velocity	The room receives the design supply air; in unidirectional zones, the air velocity over the work area is within range.	As built / at rest
Installed filter leak test	HEPA filters, gaskets and frames have no leaks after installation.	As built / at rest
Pressure difference	Each room holds its design pressure relative to neighbouring rooms, so air flows from cleaner to less clean areas.	At rest
Airflow direction and visualisation	Air moves the way the design intends, particularly over critical zones and at doors.	At rest, then in operation
Recovery	How quickly the room returns to its clean state after a particle challenge (100:1 recovery time).	At rest
Temperature and humidity	The room holds the conditions the process and people need.	At rest / in operation
Containment leak	Unfiltered air does not leak in from surrounding spaces through joints and penetrations.	As built / at rest
Particle classification	Airborne particle concentration meets the ISO class.	At rest and in operation

The filter leak test is described in HEPA filter in-situ leak testing. Visualisation methods for isolators, which apply equally to unidirectional zones in rooms, are in airflow visualisation smoke studies.

The order that works

1. Balance the HVAC first. Airflow volumes and room pressures are set by the HVAC contractor before formal testing. Testing an unbalanced system wastes the test.
2. Airflow. Measure supply volumes or velocities. If they are wrong, every later result changes when they are corrected.
3. Filter leak test. A leaking filter can pass a particle count on a quiet day and fail on a busy one.
4. Pressure differences. With airflow fixed, confirm the pressure cascade and door alarms.
5. Visualisation. Confirm airflow patterns, especially at critical zones and between rooms.
6. Recovery. Measure how fast the room cleans up after a challenge.
7. Particle classification at rest, then in operation with people and process present.

If any test fails, correct the cause and repeat the tests that depend on it. A change to supply airflow, for example, means repeating pressure, recovery and classification.

Occupancy states

• As built: the installation is complete and running, with no production equipment or people.
• At rest: production equipment installed and operating as agreed, but no people present.
• In operation: the room working normally, with the agreed number of people.

Agree the state for each test in the protocol. An “in operation” classification should reflect a realistic worst case — the maximum number of people and the most particle-generating activities — not a quiet shift.

How many locations and how long

The number of sampling locations for classification comes from the room area, and the sample volume from the class limit of the largest particle size considered. The ISO 14644-1 calculator works both out. For recovery, the air change and recovery time calculator gives an estimate to compare the measured value against.

Requalification

Test	Repeat
Particle classification	ISO 14644-2: at most every 6 months for ISO 5 and cleaner, at most every 12 months for other classes
Other tests (airflow, filter leak, pressure, recovery, visualisation)	At intervals set by risk assessment and the site’s qualification policy
After a change	Repeat the tests the change can affect: filter replacement, HVAC modification, layout change, extended shutdown

Continuous or frequent monitoring that shows the room stays in control can support the requalification decision, but it does not replace requalification.

What the report should contain

• The room, its class and the occupancy state for each test.
• Test methods with reference to ISO 14644-3 or the site procedure.
• Instrument identification and calibration status.
• Locations on a drawing, raw results and the acceptance criteria.
• Deviations, their investigation and any retests.