The European committee for standardization (CEN) had established this standard (EN779:2012) and it contains the requirements that dust filters must meet, describes test methods and the test bench to measure the performance of General Ventilation Air filters. The standard is purposed to classify air filters based on their lowest filtration efficiency. This lowest efficiency was referenced to as Minimum Efficiency (ME). Filters are tested with an air flow rate between 0.24 m³/s (850 m³/h) and 1.5 m³/s (5400m³/h).
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 currently existed in the market.
The standard helps to eliminate many problems presented by electrostatic charged synthetic filters. While such filters can display and provide good initial filtration efficiency, they discharge extremely rapidly. This entails a considerable degradation in their air cleaning ability. Unlike synthetic fiber, glass fiber is not affected by the loss of the electrostatic charge and maintains its efficiency during its whole life cycle, thereby ensuring performance levels that meet the limits set by regulations for the filter’s entire operating life.
The air filter classification for fine filters F7 to F9 was based on this minimum efficiency (ME). ME is defined as the lowest value of three different tests for 0.4 μm particles; initial efficiency, efficiency throughout the test’s loading procedure and discharged efficiency.
Unfortunately, one result of the subject discussion is that too many entities were using F7 class filters that have ME values of between 5 and 10 percent. This means that as much as 90 to 95 percent of the contaminants in the outdoor air find their way into buildings and pollute the indoor environment.
By basing classification on ME value, the standard forces these filters out of the market. At the same time, it will contribute to the development of synthetic filter materials offering considerably higher particle separation.
Fine filters previously rated as F5 & 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. Thus, the new EN779 enables customers to better select the air filtration solution that complies with their actual air quality demands.
According to this standard, filter elements fall into one of the following Groups:
— Coarse filters (G1, G2, G3, G4);
— Medium filters (M5, M6);
— Fine filters (F7, F8, F9).
The table shows the various classifications of per EN 779:2012
“NOTE
Minimum efficiency is the lowest of any of the following three values: initial efficiency, discharged efficiency or efficiency throughout the test’s loading procedure.”
(All above information & Data are derived from Book records of Filtration Standards & Other related standards, research papers and its related webpages)