TEST METHODS
There are basically two sources for filter testing; USA based standards (ASHRAE, IEST; MIL) or European based standards (CEN; EN779 and EN1822). For coarse dust filters ASHRAE specifies weight based filter efficiency called Average Weight Arrestance and Average Atmospheric Dust Spot Efficiency based on staining for fine dust filters. On the other hand the new EN779 : 2002 is used both for coarse and fine filters which utilizes a challenge aerosol DEHS (or equivalent) where upstream and downstream samples we analyzed by an optical particle counter to provide filter particle size efficiency data.
For HEPA and ULPA filters similarly CEN standards are used in Europe, IEST and MIL recommended practices are used in the United States. The filter efficiency is defined at 0.3 µm particle size for HEPA filters in IEST standards. In contrast, EN1822 defines the filter efficiency at MPPS`s (Most Penetrating Particle Size). The filter test methods also differs in these two standards. IEST recommends particle counters and photometers for filter tests, while EN1822 requires particle counters.
ULPATEK filters are tested both for European (CEN) and USA standards according to user requirements. Individual test certificates are available for HEPA and ULPA filters.