Need DOP testing or HEPA integrity testing for a cleanroom, cabinet or controlled air system? Vivid Air can assist with cleanroom testing and validation services.
Understanding DOP Testing
A DOP test is an aerosol-based leak test used to verify the integrity of a HEPA filter, its seals and its housing. The following points explain how the test is used and why it remains an important part of HEPA filter integrity testing:
- DOP traditionally refers to dioctyl phthalate, the aerosol historically associated with this type of testing. Although alternative aerosol challenge media are now commonly used, DOP testing remains the widely recognised industry term for HEPA filter integrity testing.
- The test checks the filter media, seals, gaskets, frame and housing.
- Modern testing uses alternative aerosols, such as PAO, DEHS or Shell Ondina depending on the method, equipment and applicable standard. Dioctyl phthalate is largely phased out due to its status as a suspected carcinogen.
- A filter can look correctly installed and still fail if air is bypassing the filter through a weak seal or housing.
The DOP Testing Process:
Vivid Air conducts DOP and HEPA filter integrity testing in accordance with ISO 14644-3.
1
Inspect the system, filter housing and visible condition.
2
Prepare the aerosol testing equipment.
3
Challenge the HEPA filter with the test aerosol.
4
Sample the upstream aerosol to confirm its presence and correct concentration.
5
Identify leaks or areas of concern.
6
Record results and recommend corrective action where required.
7
Retest after repair, replacement or adjustment if needed.
Once testing has been completed, Vivid Air issues a Validation Certificate in accordance with ISO 14644-3 requirements.
How DOP testing supports filter integrity testing
Filter integrity testing checks whether a HEPA filter is performing properly as part of the installed system.
That distinction matters. Once installed, a HEPA filter becomes part of a complete filtration system. The filter media, frame, seals, gaskets and housing all contribute to its performance. If any one of these components allows air to bypass the filter, the system may no longer provide the level of protection it was designed to deliver.
DOP testing is one method commonly associated with this process. It helps show whether particles are passing through or around the filter where they should be contained.
A filter integrity test is commonly needed after installation, filter replacement, maintenance or when clean air performance is questioned.
If you are replacing filters and need to confirm both product suitability and testing requirements, explore Vivid Air’s HEPA filters and air filtration systems or speak to the team about the correct validation scope.
What does a DOP or HEPA integrity test check?
When you’re relying on a HEPA filtration system, you need confidence that it’s performing as intended. That means looking beyond the filter itself to the components that keep the system sealed and functioning correctly.
During a DOP test, the following areas are typically assessed:
Filter media
Checks for damage, weak points or unwanted particle penetration through the filter material.
Seals and gaskets
Identifies leaks around sealing surfaces where air may bypass the filter.
Filter frame and housing
Checks whether the frame is seated correctly and whether the housing prevents bypass leakage.
Leak paths
Looks for routes where particles may pass through or around the filter assembly.
Installation condition
Confirms whether the filter has been fitted, seated and sealed correctly after installation, replacement or maintenance.
Airflow-related concerns
Helps identify whether airflow behaviour may be contributing to uneven loading, leakage or performance concerns.
Which systems require DOP testing?
DOP testing is used across a wide range of clean air systems that rely on HEPA filtration. The equipment may differ, but the objective is the same: to confirm that the installed filtration system is performing as intended.
These are the environments where filter integrity testing is most commonly carried out.
Cleanrooms
Verifies that installed HEPA filtration is supporting required air cleanliness and broader cleanroom testing records.
HEPA Filter Housings and Filter Banks
Checks for leaks around the filter, seals and housing to support DOP testing of HEPA filters and filter integrity testing.
Biosafety cabinets
Confirms HEPA integrity testing after installation, maintenance or filter replacement to support safe cabinet operation.
Fan Filter Units
Verifies clean airflow delivery and filter installation integrity in fan filter units.
Cleanroom Pass Boxes
Checks filter integrity where controlled material transfer forms part of the cleanroom process.
Related pathway: cleanroom pass boxes
Where HEPA filtration or controlled airflow forms part of the system design, filter integrity testing may be combined with fume cupboard validation.
When should filter integrity testing be done?
- After HEPA filter installation
- After HEPA filter replacement
- After maintenance or repairs
- After equipment is moved
- During broader cleanroom testing or validation
- Before audits or internal compliance checks
- When contamination, airflow or performance concerns are suspected
Vivid Air recommends that testing intervals be determined in accordance with the applicable industry standards and the requirements of the specific application.
What happens if a HEPA filter fails integrity testing?
A failed filter integrity test does not mean the whole system has failed. It means a leak, fault or installation issue has been identified and needs to be investigated before the system can be confirmed as performing correctly.
The issue may be linked to damaged filter media, poor sealing, gasket failure, housing condition, incorrect installation or disruption after maintenance.
A practical next-step process looks like this:
1
Identify the failed area or leak point.
2
Check whether the issue relates to the filter media, seal, gasket, frame, housing or installation.
3
Recommend corrective action where required.
4
Repair, adjust or replace the affected component.
5
Allow the system to stabilise if needed.
6
Retest the affected area.
7
Update the documentation once results are confirmed.
This is why HEPA integrity testing should be treated as part of a validation process, not only as a pass or fail exercise. The goal is to understand the issue, correct it and confirm the result.
DOP Testing and ISO 14644-3: What to Know
The term DOP testing remains widely used within the cleanroom and controlled-environment industries to describe HEPA filter integrity testing, even where a different aerosol challenge medium is used.
Vivid Air uses Shell Ondina as the aerosol challenge medium during its DOP testing procedures. Testing is conducted in accordance with ISO 14644-3 to assess whether aerosol is passing through the HEPA filter media, seals, frame, housing or other potential leakage paths.
Once testing has been completed, Vivid Air issues a Validation Certificate in accordance with ISO 14644-3 requirements.
Where GMP Annex 1 requirements apply, the permitted local leakage must not exceed 0.01% of the upstream challenge concentration.
For broader cleanroom validation support, Vivid Air can assist with cleanroom testing and validation services.
Common Mistakes With Filter Integrity Testing
How to Avoid Unreliable Test Results
Accurate testing depends on the right scope, timing and interpretation. Most failed or inconclusive test results can be traced back to these common oversights.
Assuming a new HEPA filter automatically passes
A new filter can still fail if it is damaged, poorly seated or installed in a housing that allows bypass leakage.
Only checking the filter media
A DOP test should consider the full filter installation. Seals, gaskets, frames and housings can all create leak paths.
Testing before the system has stabilised
After maintenance, cleaning, repair or filter replacement, the system may need time to stabilise before testing gives a reliable picture.
Not retesting after corrective work
If a leak is repaired or a filter is adjusted, retesting helps confirm that the issue has been resolved.
Replacing filters without checking the housing
A failed result is not always caused by the filter itself. The housing, seals or installation conditions may be part of the problem.
Treating DOP testing as a once-off admin task
DOP testing should support real system confidence, not only documentation. The result should help your team understand whether the clean air system is performing correctly.
Related clean air and validation solutions
DOP testing is often one part of a broader clean air, filtration or validation requirement. These related pathways can help you move from the test result to the next practical step.
Need DOP testing or HEPA filter integrity testing?
The right testing approach depends on your equipment, how it’s used and what you’re trying to verify. Whether you’re commissioning a new installation, replacing HEPA filters or preparing for an audit, choosing the correct scope is the first step towards reliable results.
If you need DOP testing, filter integrity testing or HEPA integrity testing, Vivid Air can help define the right testing scope for your cleanroom, cabinet or controlled air system.