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In 2002, the European Committee for Standardization introduced a new standard. EN779:2002 for general ventilation filters. The test procedures described in this standard have been developed from those used in previous standards EN779:1993 and Eurovent 4/9:1997 where air-flow, pressure drop, arrestance and filtration efficiency are all measured and filters classified according to the results obtained.
The EN779:2002 classification system comprises of groups F and G filters with classification determined from the average filtration efficiency with respect to neutralised DEHS particles of 0,4 μm diameter. Filters found to have an average efficiency value of less than 40% will be allocated to group G and the efficiency reported as “<40%”. The classification on G filters is based on their average arrestance with the loading dust. Initiatives to address the potential problems of particle re-entrainment, shedding and the in-service charge neutralisation characteristics of certain types of media have been included in annexes A and B.
Filters are classified according to their efficiency (arrestance) under the following test
• The air flow shall be 0,944 m3/s (3400m3/h) if the manufacturer does not specify any rated
air flow rate;
• 250 Pa maximum final pressure drop for Coarse (G) filters;
• 450 Pa maximum final pressure drop for Fine (F) filters.
If the filters are tested at 0.944 m3/s and at maximum final pressure drops, they are classified according to the table below. For instance G3, F7. Filters tested at airflows and final pressure drops different from those above shall be classified according to the table. However the classification shall be qualified by test conditions in parentheses, e.g. G4 (0,7m3/s, 200 Pa), F7 (1.25 m3/s).
The European Committee for Standardization (CEN) has established a new standard for general ventilation air filters, EN779:2012.
Where the existing EN779:2002 was already widely accepted as a standard for testing and classifying coarse and fine filters based on average efficiency, the revised standard is an important step forward. The main changes can be summarized as follows:
• Implementation of minimum efficiency (ME) requirements for fine filter classes F7 to F9.
• ME as the lowest value of initial efficiency, efficiency throughout the test’s loading procedure and discharged efficiency.
• Fine filter classes F5 and F6 are renamed to M5 and M6 and are part of new medium filter category.
Those air filters that do not meet the ME requirements will lose their original efficiency classification and will automatically drop one or more classes. With this revised methodology, the new EN779 will address the negative effects on Indoor Air Quality (IAQ) caused by underperforming air filters that are currently sold in the market. Although often demonstrating compliant average efficiencies, it is well known that some air filters lose their particulate collection functionality over time and therewith become a gateway for airborne contamination in buildings. The new ME requirements of EN779:2012 will stimulate the development of higher quality fine filters for contributing to people breathing in purer air for improved health and comfort. Fine filters rated as F5 or F6 to EN779:2002 are not required to meet an (ME) value in the new situation. To clearly differentiate these from those that do, filter classes F5 and F6 have been renamed to M5 and M6 as part of a new medium filter category.