How to Conduct HEPA Filter Integrity Test procedure? DOP Test

The HEPA filter integrity test is typically performed on cleanroom supply air HEPA filters using a photometer to scan the filter surface for pinhole leaks that could allow the transmission of contaminant particles that would be unacceptable in a critical application.

What is DOP Test?
The DOP test, also known as the DOP aerosol test, is a standardized procedure used to evaluate the performance of high-efficiency particulate air (HEPA) filters. The test involves generating aerosol particles of a known size and concentration, typically using dioctyl phthalate (DOP), and passing them through the filter under controlled conditions.

The objective of the DOP test is to determine the filter's efficiency at capturing particles of a specific size, typically 0.3 microns. The efficiency of a filter is defined as the percentage of particles of a specific size that are captured by the filter. For example, a filter with an efficiency of 99.97% for 0.3-micron particles means that 99.97% of particles of this size are trapped by the filter.

The DOP test is used in a variety of industries, including healthcare, pharmaceuticals, aerospace, and electronics manufacturing, to ensure that HEPA filters are working effectively to prevent the spread of airborne contaminants.

Which test is used for the validation of the HEPA filter?
Dispersed Oil Particulate (DOP) testing, also known as filter integrity testing, is the process in which the integrity of your HEPA (High-Efficiency Particulate Air) or ULPA (Ultra Low Penetration Air) filter is challenged by introducing particulates and measuring the output.

  1. Keep the instrument in the area.
  2. Ensure that the instrument used for DOP testing is calibrated and calibration is valid.
  3. Provide Nitrogen / Compressed air to the DOP smoke generator.
  4. Keep the smoke generator in the supply air plenum.
  5. Smoke will travel through the supply air and come out through HEPA Filter.
  6. Check the 100% concentration before filtering.
  7. Move the sensing probe at not more than 10 feet per minute at a maximum of 1 inch under the HEPA Filter complete area.
  8. If leakage is there, the needle on the dial will show the deflection, Tighten the filter properly and again repeat the above procedure.
  9. If the penetration of smoke is less than the acceptable limit the filter passes the DOP test.
  10. If the probe shows penetration more than the acceptable limit within the area of the filter, then the filter is leaking. So replace the filter and repeat the above procedure.
  11. Collect the test certificates from the outside agency and check as per requirement.
  12. Take five readings with vane type Anemometer in a plane parallel to and 6 inches downstream of the HEPA filter in feet per minute. (four corners and one center).
  13. Note down the reading and calculate the average velocity.
  14. If the velocity is less than the acceptable limit, check and reset the damper. Even after correction if the velocity is below the acceptable limit, the filter is choked and replaced the same.
  15. Carry out the above test on the new filter.
  16. Carry out the above qualification once in a year.

Post a Comment


  1. Sir, this practice has been upgraded with the Poly Alfa Olefin & scanning rate of the filter to per second with complete upstream concentration micro gram per ml.