What DOP Testing Is

  • A method used to verify that installed HEPA/ULPA filters are functioning correctly and not leaking contaminants back into the environment
  • Historically used dioctyl phthalate (DOP) as the aerosol, but modern tests use safer alternatives such as PAO or Shell Ondina oil. 

How It Works

  • A high‑concentration aerosol is released upstream of the filter.
  • A calibrated photometer scans downstream to detect any penetration of particles.
  • The process checks the filter media, frame, seals, joints, and housing for leaks

Why It’s Important

  • Ensures the integrity of cleanrooms, healthcare environments, LEV systems, spray booths, and other controlled spaces
  • Confirms compliance with standards such as BS EN ISO 14644‑3 and BS EN 1822. 
  • Identifies poorly installed, damaged, or degraded filters before they compromise safety. 

When It Should Be Performed

  • At installation, after damage, when performance is suspected to be compromised, or at intervals defined by risk assessment (commonly every 6 months in cleanrooms

DOP testing remains a critical validation method for ensuring HEPA/ULPA filtration systems maintain required performance and regulatory compliance.