The standards EN 779 and ASHRAE 52.2 both pertain to the testing and classification of air filters used in ventilation systems, but they differ primarily in the regions of application and the specifics of their testing methods.

  1. EN 779: This was a European standard, replaced by ISO 16890 in 2016. EN 779 classified filters based on their average efficiency over the range of 0.4 micrometers particle size. It provided ratings such as G1-G4 (coarse filters), M5-M6 (medium filters), and F7-F9 (fine filters). The tests involved using synthetic dust and measuring the filter's ability to retain particles.
  2. ASHRAE 52.2: This standard, from the American Society of Heating, Refrigerating and Air-Conditioning Engineers, is still in use primarily in North America. It introduces the Minimum Efficiency Reporting Value (MERV) to classify filters based on their efficiency in capturing particles in different size ranges (ranging from 0.3 to 10 micrometers). This standard employs a more detailed testing procedure that includes loading the filter with dust to see how it performs over time, thus giving a clearer picture of its performance in real-world conditions.

The key differences between EN 779 and ASHRAE 52.2 therefore include:

  • Scope and application: EN 779 was specific to Europe and has since been superseded by ISO 16890, while ASHRAE 52.2 is widely used in North America.
  • Testing methods: ASHRAE 52.2 uses a broader range of particle sizes for testing and evaluates filter performance under conditions that simulate actual usage more closely.
  • Efficiency classification: EN 779 used a simpler classification system based mainly on average efficiency, whereas ASHRAE 52.2 uses the MERV rating system, which accounts for performance across a range of particle sizes and under conditions of filter loading with dust.

These distinctions make ASHRAE 52.2 more detailed in terms of evaluating the performance of filters under more realistic conditions compared to the older EN 779 standard.

The difference between EN 779 and ASHRAE 52.2 standards is particularly relevant in the flexography industry primarily due to the critical role that air filtration plays in maintaining print quality and machine functionality. Flexography involves the use of fast-drying inks and precise graphic reproduction, often on non-absorbent materials like plastics and metals, which makes the environment prone to airborne contaminants.