When a cleanroom manager takes over from a predecessor, the HEPA filter test reports are usually the first document reviewed. Yet the language inside those reports – DOP, PAO, upstream challenge concentration, downstream scan – can feel deliberately opaque.
At its core, an integrity test asks one question: does aerosol pass through the filter media or around the gasket? Everything else is procedural detail. The aerosol is injected upstream at a known concentration, and a photometer sweeps the downstream face looking for leaks larger than 0.01 percent of the upstream reading.
DOP (Di-Octyl Phthalate) is the classic challenge fluid but has fallen out of favour due to toxicity concerns. PAO (Poly Alpha Olefin) is chemically similar, safer, and now the industry default in India and much of Europe. Both give equivalent results when tested with modern photometers.
For most pharma applications, we recommend integrity testing at installation, after any major HVAC change, and every twelve months routine. Recording data digitally makes trend analysis painless during audits, so avoid PDF-only reports whenever possible.