Testing Guides

Cleanroom Test Failed? Common Causes and How to Fix Each One

By QV TEST engineering team · Published 27 Oct 2026 · Updated 27 Oct 2026 · 7 min read

Summary table

Confirm the result first

A failed result is sometimes caused by the measurement conditions rather than the system. Before fixing anything, check four things.

• Instruments: ISO 14644-3:2019 expects each instrument to have a valid calibration certificate, for example the pressure gauge (B.1.3) and temperature sensors (B.5.2).
• System state: before measuring room pressure differences, the air system should be running and stable, supply airflow within specification, doors and pass boxes closed, and extraction running as agreed (B.1.2).
• Measuring points: do not measure close to supply diffusers, return grilles or doors, where local air velocity distorts the reading (B.1.2).
• Occupancy state: check that the test was done in the as-built, at-rest or operational state that matches the acceptance criteria.

Airflow or air velocity failure

Airflow underpins almost every other result. If there is not enough air, room pressure and particle counts usually suffer too. The common causes fall into four groups.

1. Filters: clogged pre-filters or HEPA filters, or filters of the wrong specification, raise resistance above design. Check the pressure drop across the filters.
2. Fan and AHU: a slack or slipping belt, dirty blades, a motor running in reverse, or a VFD frequency set too low.
3. Ductwork: duct leakage, dampers stuck closed or set wrongly, or obstructions in the duct.
4. Controls and layout: a drifting pressure sensor that controls the fan, or new partitions added without rebalancing the air system.

Once the cause is fixed, rebalance every diffuser before re-testing to ISO 14644-3 clause B.2. If duct leakage is suspected, a duct leakage test can confirm it.

HEPA filter leaks

ISO 14644-3:2019 clause B.7.2.4 treats a reading above 0.01% of the upstream concentration as a leak, and uses 0.1% for filters with an MPPS efficiency from 99.95% up to less than 99.995%.

Repair: clause B.7.6 allows leaks in the filter media, sealant or grid to be repaired. The repair method must be agreed between the customer and the supplier and should follow the filter manufacturer’s instructions. Repair materials should be chosen with outgassing and deposition on products in mind. Once the repair has cured, the spot must be rescanned with the same method.

Leaks at the frame: check whether the gasket or gel seal is worn, broken or not fully seated, and tighten the clamps evenly on every side.

Replacement: if the media is damaged or leaks in several places, stop the air supply, clean the housing, install a new filter and leak-test it again after installation.

Room pressure difference failure

PIC/S GMP Annex 1 in PE 009-16 (clause 53) recommends 10–15 Pa between rooms of different grades; PE 009-17 (clause 4.14) recommends at least 10 Pa. Both are guidance values. In Thailand, the 2026 MOPH notification allows Annex 1 of PE 009-16 to be used until 31 December 2029.

Room pressure comes from the difference between supply air and return or exhaust air, so confirm that airflow passes first, then adjust the return or exhaust for each room. Check for leaks at door edges, penetrations and ceilings. Where the measured difference is below the agreed value, ISO 14644-3 clause B.1.2 recommends confirming the direction of flow between rooms with flow visualization.

Humidity failure

ISO 14644-3 clause B.6 does not set a fixed humidity value. It tests whether the system holds humidity within the limits and over the period agreed between the customer and the supplier. The ASHRAE Design Guide for Cleanrooms, section 9.2, gives an example of a specification written as a set point with a tolerance, such as 45±5% RH, or as a dew point.

Too humid: check that the cooling coil is cold enough to remove moisture, look for outside air leaking in and blocked or wet drain pans, and consider adding a dehumidifier.

Too dry: check that the humidifier works and whether too much dry outside air is being brought in.

Temperature out of specification

As with humidity, ISO 14644-3 clause B.5 tests against the agreed control limits, using sensors with the accuracy given in ISO 7726 and a valid calibration certificate.

Too warm: dirty coils, a refrigerant leak, a faulty expansion valve or compressor, or extra heat load from newly installed equipment.

Too cold: an unsuitable set point or deadband, a drifting sensor, a reheat that is not working, or a chilled-water valve stuck open.

Calibrate the control sensors first. If a sensor reads wrong, adjusting the cooling system will not solve the problem.

Particle counts too high

Particle counts reflect several systems at once, so check them in this order.

1. HEPA leaks, with an installed filter leak test
2. Clogged or worn pre-filters that overload the final filters
3. Room pressure lower than the next room, which lets air flow in from a dirtier area
4. Airflow or air change rate below design
5. Gowning, staff movement, and cleaning methods and materials
6. Leaks in walls, ceilings, penetrations and door edges

If the room passes at rest but fails in operation, look at people and activity first, since the air system and filters already meet the limits when the room is empty.

Re-testing after the fix

The failed tests must be repeated, and tests that the fix may affect should be repeated too. For example:

• HEPA filter replaced or repaired: leak test, airflow and particle count
• Air rebalanced or fan settings changed: airflow, room pressure difference and particle count
• Cooling or humidity system fixed: temperature and humidity over the agreed period

The NEBB Procedural Standards for Certified Testing of Cleanrooms (clause 9.5) list airflow velocity and volume, HEPA installation leak, particle count classification and room pressurization as the primary tests, performed in the order that suits the project. In practice, confirming airflow and leaks before counting particles reduces repeat tests.

FAQ

References

• ISO 14644-3:2019 Cleanrooms and associated controlled environments — Part 3: Test methods, clauses B.1, B.2, B.5, B.6, B.7.2.4 and B.7.6
• PIC/S GMP Guide PE 009-16, Annex 1 clause 53, and PE 009-17, Annex 1 clause 4.14
• Thai Ministry of Public Health Notification on Rules and Procedures for Drug Manufacturing, B.E. 2569 (2026)
• ASHRAE Design Guide for Cleanrooms: Fundamentals, Systems, and Performance, section 9.2 Humidity
• NEBB Procedural Standards for Certified Testing of Cleanrooms (CPT), Section 9, clause 9.5

Testing Guides

DQ, IQ, OQ and PQ: What Are They and How Do They Differ?

By QV TEST Engineering Team · Published 26 Oct 2026 · Updated 26 Oct 2026 · 3 min read

Every stage starts from the URS

Annex 15, clause 3.2, requires the specification for equipment, facilities, utilities or systems to be defined in a User Requirements Specification (URS) and/or a functional specification. The URS is the reference point throughout the qualification life cycle, and clause 3.3 requires compliance with the URS to be demonstrated during DQ.

What does each stage do?

Between DQ and IQ there may be a Factory Acceptance Test (FAT) and a Site Acceptance Test (SAT), clauses 3.4–3.7. Some of their results can replace repeat testing in IQ/OQ if justified and if it is shown that transport and installation did not affect function (clause 3.6).

How do IQ and OQ differ?

IQ checks what was installed. Under clause 3.9 this includes verifying installation of components, instrumentation, equipment, pipework and services against engineering drawings, collecting operating and maintenance instructions, calibrating instruments and verifying materials of construction. OQ, under clause 3.11, tests that the system operates as designed, including upper and lower operating limits or worst-case conditions.

OQ normally follows IQ, but depending on complexity some equipment can be qualified as a combined IOQ (clause 3.10). Completing OQ allows operating and cleaning procedures, training and maintenance requirements to be finalised (clause 3.12).

What happens after PQ?

Annex 15, clause 4.1, requires equipment, facilities, utilities and systems to be evaluated at an appropriate frequency to confirm they remain in a state of control. Clause 4.2 states that where requalification is done on a time basis, the period must be justified and the evaluation criteria defined. The principles of Annex 15 also require the impact of any planned change on the qualified state to be assessed.

Frequently asked questions

References

• PIC/S Guide to Good Manufacturing Practice for Medicinal Products, PE 009-16 (1 February 2022), Annex 15: Qualification and Validation, clauses 2.10, 3.1–3.14 and 4.1–4.2 (same text as EU GMP Annex 15)
• ISO 14644-1:2015 and ISO 14644-3:2019 (cleanroom test methods)

Testing Guides

Warehouse Temperature Mapping: How Is It Done and How Many Sensors Do You Need?

By QV TEST Engineering Team · Published 26 Oct 2026 · Updated 26 Oct 2026 · 4 min read

What is temperature mapping and when is it required?

Temperature mapping is a study of how temperature is distributed in a storage area. It shows the temperature profile across the area both empty and under normal loading, identifies zones where product should not be stored (for example near cooling coils, cold air streams or heat sources), and finds the right positions for monitoring sensors. The main reference is WHO Technical Report Series, No. 961, 2011, Annex 9: Model guidance for the storage and transport of time- and temperature-sensitive pharmaceutical products, Supplement 8: Temperature mapping of storage areas (May 2015).

Under Supplement 8, clause 1.1, every temperature-controlled storage area should be mapped before it is commissioned and put into use. It should be re-mapped after any significant modification and, depending on the routine monitoring strategy, periodically, for example every three years.

What does Thai law require?

The Ministry of Public Health Notification on criteria, methods and conditions for the distribution of modern medicines B.E. 2564 (2021; in force 1 January 2022), clause 3.3.2, requires a temperature mapping study of medicine storage areas before use, under conditions representative of actual storage. Temperature monitoring devices must be installed at the critical points identified by the study, and after any significant change the risk must be assessed and the mapping repeated.

Clause 9.4.4 also requires temperature mapping of the product compartment of temperature-controlled vehicles, taking seasonal temperature variation into account.

How many sensors do you need?

Supplement 8, clause 2.1, calls for a “sufficient number” of data loggers to show the full temperature distribution. Clause 2.2.6, step 5, recommends a risk-based approach together with these placement principles:

• Horizontal: a grid along the length and width of the area, every 5–10 m (up to 20–30 m in very large facilities), matched to where product is actually stored.
• Vertical, ceiling 3.6 m or lower: three stacked levels, high, medium and low, for example at floor level, 1.2 m and 3.0 m.
• Vertical, ceiling above 3.6 m: vertical arrays at the bottom, middle (several levels) and top, for example at 0.3, 1.8, 3.6 and 5.4 m in a 6 m high store.

Worked example: a 30 × 20 m store with a 3 m ceiling and 10 m spacing gives 4 rows along the length (0, 10, 20, 30 m) and 3 rows across the width (0, 10, 20 m), so 12 positions × 3 levels = 36 points. The count is then adjusted for the racking layout, air supply positions and heat sources recorded during the site survey (step 3).

How long should you record, and in how many seasons?

• Duration (clause 2.2.6, step 9): there is no fixed rule. Warehouses and ambient areas are typically recorded for at least 7 consecutive days, including 5 working days and 2 weekend days. Cold rooms and freezer rooms are typically recorded for 24–72 hours, or longer if justified.
• Seasons (clause 2.2.4): areas affected by seasonal changes may need mapping at least twice, in the hottest and coldest periods of the year. Cold rooms and freezer rooms generally do not need two-season mapping.

What are the steps?

1. Survey the area: dimensions, racking layout, air supply positions and existing sensors.
2. Write the protocol: acceptance criteria and the number and positions of data loggers.
3. Place calibrated data loggers to the plan, horizontally and vertically.
4. Record continuously for the defined period.
5. Analyse the data to find hot spots, cold spots and any excursions.
6. Report the results with temperature distribution maps and recommended monitoring sensor positions.

Frequently asked questions

References

• WHO Technical Report Series, No. 961, 2011, Annex 9: Model guidance for the storage and transport of time- and temperature-sensitive pharmaceutical products
• Supplement 8: Temperature mapping of storage areas (WHO, May 2015), clauses 1.1, 2.1, 2.2.4 and 2.2.6 (steps 3, 5 and 9)
• Thai Ministry of Public Health Notification on criteria, methods and conditions for the distribution of modern medicines B.E. 2564 (Royal Gazette, 21 May 2021), clauses 3.3.2 and 9.4.4