How is a DOP HEPA Filter Test Carried Out?

How is a DOP HEPA Filter Test Carried Out?

HEPA Filter testing is carried out using the following procedure.

Our engineers carry out an inspection of the air supply system to identify a smoke injection point; and a safe means of injection ascertained. If it’s found that pre and secondary filters need to be removed, power to the air handing unit must be isolated before the filter removal. If the DOP is to be injected downstream of the fan unit or in a positive pressure section of duct-work a blower pump will be set up adjacent to the injection point. Thereafter, an aerosol generator will be set up adjacent to the blower pump and power up the generator to warm up. If extension leads are required, we will ensure all cables are secured as not to present a tripping hazard.


Then an aerosol photometer will be set up in accordance with the filter manufacturer’s instructions and attached to sample points; this will be fitted upstream of each HEPA filter under test. Whilst working in pairs our engineer operating the photometer will maintain regular communication with the support engineer controlling the smoke generator by means of site radio and/or mobile phones.

Using a photometer instrument, our engineer will measure upstream concentration of aerosol, calibrating as required. The DOP may need to be increased or decreased. The penetration of aerosol will then be measured using a photometer, scanning the filter face with measured overlapping strokes at a speed no greater than 5cm/s.  The ISO 14644 Part 3 standard permits a maximum downstream limit of 0.01% penetration. Filter differential pressures and airflow volume will be measured using a micro manometer and an anemometer at suitable positions.

DOP HEPA Filter Test

Using our vast technical knowledge along with our steadfast commitment to quality we provide our clients with reliable and proactive clean room testing service. We ensure that we provide accurate and thoroughly document clean room testing results, ensuring optimal cleanroom performance, documented regulatory and quality compliance, and minimised facility down time.

If you would like to know more about our cleanroom testing service please don’t hesitate to contact us on or call Darren direct on 07775623464.