EN 1822, High efficiency air filters EPA, HEPA and ULPA, consists of the following parts: Part 1: Classification, performance testing, marking Part 2: Aerosol production, measuring
General
To evaluate the efficiency of the test filter, it is securely mounted in the test filter assembly and exposed to a test air volume flow that matches the nominal volume flow rate Following the measurement of the pressure drop at this nominal rate, the filter is cleaned with pure air Subsequently, the test aerosol generated by the aerosol generator is blended with the prepared test air in a mixing section, ensuring a uniform distribution across the duct's cross section.
The efficiency of filtration is assessed based on the most penetrating particle size (MPPS) as outlined in EN 1822-3 Additionally, the aerosol particle size distribution can be measured using a particle size analysis system, such as a differential mobility particle sizer (DMPS).
Testing can be conducted with either monodisperse or polydisperse test aerosols For (quasi-)monodisperse aerosols, the total particle counting method is applicable using a condensation nucleus counter (CNC) or an optical particle counter (OPC), such as a laser particle counter It is essential to ensure that the number median particle diameter aligns with the most penetrating particle size (MPPS), which is the particle diameter at which the filter medium exhibits its lowest efficiency.
When working with a polydisperse aerosol, it is essential to utilize an optical particle counter that not only counts particles but also measures their size distribution It is important to ensure that the median diameter \(D_M\) of the test aerosol falls within the specified range.
To assess integral efficiency, representative partial flows are collected from both the upstream and downstream sides of the filter element These flows are then directed to a particle counter to quantify the number of particles present.
The integral efficiency can be determined using one of two methods, either
with fixed test sampling probes (see 4.2); or
with one or several movable sampling probes downstream (scan method) (see 4.3)
Both methods utilize a fixed sampling probe to collect upstream samples The number concentrations for both upstream and downstream, along with the integral efficiency, are determined based on particle counts, sampling duration, and the flow rate of the sampling volume.
Measurement method using fixed sampling probe
This method involves using a fixed sampling probe to collect the downstream sample for assessing integral efficiency It is essential to include a mixing section after the test filter to ensure that the aerosol is uniformly mixed with the test air across the duct's cross section (refer to section 6.2.4).
Scan method
The efficiency of the integral can be assessed by averaging the results obtained from the leak test using the scan method, as outlined in EN 1822-4.
The scan method involves downstream sampling conducted immediately behind the test filter using one or more movable sampling probes These probes can navigate the entire cross-sectional area of the filter and its frame, ensuring overlapping tracks without any gaps.
The test apparatus is similar to that used with stationary sampling probes, but it features a three-dimensional tracking system that moves the probe(s) instead of a downstream mixing section To prevent contaminated outside air from entering the test airflow, measures must be taken, especially since the test duct is typically open The configuration of this test apparatus is detailed in EN 1822-4.
The scan method aggregates all particles counted throughout the downstream scan during leak testing The sampling duration is determined based on the scanning data and the number of probes used.
The further clauses of this standard refer solely to the measuring method with fixed sampling probes where the integral efficiency is determined independently from the leak test procedure.
Statistical efficiency test method for EPA filters (Group E)
EPA filters must undergo one of the test procedures outlined in sections 4.2 and 4.3 Unlike HEPA and ULPA filters, which require individual efficiency tests for each filter element, EPA filters do not necessitate this Instead, the overall efficiency of EPA filters is established by averaging the results from the statistical efficiency tests.
A type test certificate or a factory test certificate is required to document the filter data as per Clause 10 Additionally, the supplier must provide documentary evidence to verify the published filter data upon request.
Maintaining a certified quality management system, such as EN ISO 9000, requires the implementation of statistically based methods to test and document the efficiency of all EPA filters in accordance with EN 1822 standards.
All production lots of EPA filters must be tested using accepted statistical methods, such as the "skip lot procedure" outlined in ISO 2859-1, or any equivalent alternative method.
The "skip lot procedure" outlined in ISO 2859-1 begins with a high test frequency that decreases as production experience and product conformity improve For instance, all filters from the first eight production lots are tested; if they pass, the testing frequency is halved for the next eight lots This process continues, reducing the frequency until only one out of eight lots is tested, establishing a minimum test frequency However, if any tested filter fails, the test frequency is doubled It is essential that more than three filters are tested per lot.
The filter element must be free from damage and irregularities It should be handled with care and clearly marked with essential details, including the designation of the filter element and the upstream side.
The temperature of the test filter during the testing shall correspond with that of the test air
General
A flow sheet showing the arrangement of apparatus comprising a test rig is given in Figure 4 of EN 1822- 1:2009 An outline diagram of a test rig is given in Figure 1 of this standard
This article covers the essential principles of aerosol generation and neutralization, including appropriate equipment types and comprehensive descriptions of the measuring instruments required for effective testing.
Test duct
Test air conditioning
The test air conditioning system must include all necessary equipment to regulate the test air conditions, ensuring compliance with the specifications outlined in Clause 7.
Adjustment of the volume flow rate
Filters must be tested at their nominal air flow rate, with the ability to adjust the volume flow rate by ± 5% using appropriate methods such as fan speed adjustments or dampers This adjusted flow rate should remain stable within ± 2% during each test.
Measurement of the volume flow rate
The volume flow rate must be determined using a standardized or calibrated method, such as measuring differential pressure with equipment like orifice plates, nozzles, or Venturi tubes, in compliance with EN ISO 5167-1.
The limit error of measurement shall not exceed 5 % of the measured value.
Aerosol mixing section
The design of the aerosol input and mixing section must ensure that the aerosol concentration at various points across the duct cross section, specifically in front of the test filter, does not vary by more than 10% from the average value obtained from at least nine measurement points throughout the channel cross section.
Test filter mounting assembly
The test filter mounting assembly shall ensure that the test filter can be sealed and subjected to flow in accordance with requirements
It shall not obstruct any part of the filter cross sectional area
6 Aerosol inlet to the test duct
11 Ring pipe for differential pressure measurement
14 Measuring damper in accordance with
Measuring points for the pressure drop
To accurately assess pressure drop, measuring points must be strategically placed to capture the average static pressure both upstream and downstream of the filter It is essential that the pressure measurement planes are located in areas with consistent flow and a uniform flow profile.
In rectangular or square test ducts, pressure measurement holes with diameters ranging from 1 mm to 2 mm should be drilled in the center of the channel walls, perpendicular to the flow direction These four holes must be connected by a circular pipe.
Sampling
To assess efficiency, partial flows are extracted from the test volume flow using sampling probes connected to particle counters The probe diameter must be selected to maintain isokinetic conditions in the duct at the specified volume flow rate, minimizing sampling errors due to the small particle size in the aerosol Connections to the particle counter should be kept as short as possible Representative samples are collected from the upstream side using a fixed sampling probe positioned before the test filter, ensuring that the aerosol concentration measured does not deviate by more than ± 10% from the mean value as outlined in section 6.2.4.
A fixed sampling probe is positioned downstream, following a mixing section that guarantees a representative measurement of the downstream aerosol concentration This is validated when, in the event of a leak in the test filter as per Clause 5 of EN 1822-1:2009, the measured aerosol concentration does not deviate by more than ± 10% from the mean value of at least nine measurement points across the duct cross-section.
The mean aerosol concentrations determined at the upstream and downstream sampling points without the filter in position shall not differ from each other by more than 5 %.
Aerosol generation and measuring instruments
General
The aerosol generator's operating parameters must be fine-tuned to create a test aerosol with a number median diameter that falls within the Most Penetrating Particle Size (MPPS) range for the sheet filter medium.
The median size of the monodisperse test aerosol may not deviate from the MPPS by more than ± 10 %
A deviation of ± 50 % is allowed when using a polydisperse aerosol
The aerosol generator's particle output must be calibrated based on the test volume flow rate and filter efficiency, ensuring that the counting rates on both the upstream and downstream sides remain within the counter's coincidence limits (maximum coincidence error of 5%) and are well above the instruments' zero count rate.
The concentration of number distribution for the test aerosol can be accurately assessed using an appropriate particle size analysis system, such as a differential mobility particle sizer (DMPS) or a laser particle counter designed for this purpose It is essential that the measurement method employed to determine the number median value maintains a limit error of no more than ± 20% relative to the measured value.
To ensure statistically significant results, the number of particles measured both upstream and downstream must be sufficiently large, while also remaining within the measuring range of the upstream particle counter If the particle concentration exceeds this range during counting, a dilution system should be implemented between the sampling point and the counter.
Particle counting can be performed using either two parallel counters on the upstream and downstream sides or a single counter that alternates measurements between these sides When using a single counter, it is crucial to maintain consistent properties of the test aerosol, such as number concentration, particle size distribution, and uniform distribution across the channel cross-section If employing two counters in parallel, both must be of the same type and calibrated as dual devices.
Apparatus for testing with a monodisperse test aerosol
For technical reasons, the particle size distribution produced by the aerosol generator is usually quasi- monodisperse
When using a monodisperse aerosol for the efficiency testing of the filter element, not only optical particle counters but also condensation nucleus counters may be used
When utilizing a condensation nucleus counter, it is crucial to ensure that the test aerosol does not contain significant quantities of particles much smaller than the most penetrating particle size (MPPS) Such smaller particles, potentially generated by a malfunctioning aerosol generator, can be inaccurately counted by the condensation nucleus counter, leading to substantial errors in efficiency measurements To verify this, one should assess the number distribution of the test aerosol using a measuring device that spans from the lower limit of the condensation nucleus counter up to approximately 1 µm in particle size The resulting number distribution should be quasi-monodisperse.
The test apparatus for testing with monodisperse aerosol is shown in Figure 2.
Apparatus for testing with a polydisperse test aerosol
When determining the efficiency of a filter element using a polydisperse test aerosol, the particle number concentration and size distribution shall be determined using an optical particle counter (e.g laser particle counters)
The test apparatus for testing with polydisperse aerosol is shown in Figure 3
1 Pre-filter for test air
2 Fan with variable speed control
4 Aerosol inlet in the duct
5 Aerosol generator for the monodisperse aerosol
6 Measurement of temperature, barometric pressure and relative humidity
8 Sampling point for particle size analysis
9 Particle size analysis system (DMPS or OPC)
10 Sampling point for upstream particle counting
12 Upstream particle counter (CNC or OPC)
14 Measurement of pressure drop across the test filter
15 Measurement of absolute pressure and volume air flow rate
17 Sampling point for downstream particle counting
18 Downstream particle counter (CNC or OPC)
19 Computer for purposes of control and measurement recording
Figure 2 — Test apparatus for testing with a monodisperse aerosol
1 Pre-filter for test air
2 Fan with variable speed control
4 Aerosol inlet in the duct
5 Aerosol generator for the polydisperse aerosol
6 Measurement of temperature, barometric pressure and relative humidity
8 Sampling point for upstream particle count
10 Upstream optical particle counter (OPC)
12 Measurement of pressure drop of the test filter
13 Measurement of absolute pressure and volume air flow rate
15 Sampling point for downstream particle count
16 Downstream optical particle counter (OPC)
17 Computer for control and measurement recording
Figure 3 — Test apparatus for testing with a polydisperse aerosol
The measuring range of the optical particle counter used in testing efficiency shall cover the following particle sizes:
MPPS/1,5 to MPPS x 1,5 (Range I, Figure 4)
The distribution of the size classes shall be such that each of the class limits meets one of the following conditions:
MPPS/2 < lower channel limit ≤ MPPS/1,5 (Range IIa, Figure 4)
MPPS x 1,5 ≤ upper channel limit < MPPS x 2 (Range IIb, Figure 4)
NOTE The measuring range of the optical particle counter used for efficiency testing should cover at least the following particle size range:
MPPS/1,5 to MPPS x 1,5 (Range I, Figure 4)
The channel limits are defined to include a lower limit within the diameter range of MPPS/2 to MPPS/1.5 (Range IIa) and an upper limit within the diameter range of MPPS x 1.5 to MPPS x 2 (Range IIb).
The efficiency of a filter can be assessed by evaluating all channels within specified limits It is important to note that meeting this condition does not necessitate the presence of multiple channels; even a single channel can suffice in extreme cases.
Figure 4 — Fractional efficiency E and permissible measuring ranges relative to efficiency mini- mum (MPPS = 0,18 àm) and number distribution f of a polydisperse test aerosol with d p of 0,23 àm
7 Conditions of the test air
The test air shall be conditioned before being mixed with the test aerosol such that its temperature, relative humidity and purity comply with the requirements specified in 6.1 of EN 1822-1:2009
Preparatory checks
After switching on the test apparatus the following parameters shall be checked:
Operational readiness of the measuring instruments:
The condensation nucleus counters shall be filled with operating liquid The warming-up times specified by the instrument makers shall be observed
Zero count rate of the particle counter:
The measurement of the zero count rate shall be carried out using flushing air which is free of particles
Absolute pressure, temperature and relative humidity of the test air:
These parameters shall be checked to ensure that they comply with the specifications made in 6.1 of
EN 1822-1:2009 If a parameter does not comply with the specifications made in EN 1822-1 and
EN 1822-2 then appropriate corrections shall be made.
Starting up the aerosol generator
When starting up the aerosol generator a stand-by filter element shall be installed in the test filter mounting assembly
After optimizing the aerosol generator's operating parameters and allowing for a suitable warming-up period, it is essential to verify the particle concentration and distribution of the test aerosol to meet the criteria outlined in section 6.3 The assessment of the test aerosol's distribution and concentration should be conducted as near to the filter mounting assembly as feasible.
Preparation of the test filter
Installation of the test filter
The test filter shall be handled in such a way as to ensure that the filter material is not damaged
The test filter shall be installed in the mounting assembly with regard to air flow direction and gasketing side as it is foreseen for use
The seal between the test filter and the test filter mounting assembly shall be free from leaks.
Flushing the test filter
To minimize particle self-emission from the test filter and to ensure temperature equilibrium between the test filter and the test air, it is essential to flush the test filter with test air at the nominal volume flow rate for an adequate duration After this flushing process, the remaining self-emission can be accurately assessed using a downstream particle counter.
Testing
Measuring the pressure drop
The pressure drop across the test filter must be measured in its unloaded state with pure test air The nominal volume flow rate should be established as outlined in section 6.2.2, and measurements should only be taken once a stable operating condition has been achieved.
Testing with a monodisperse test aerosol
In the mixing section, test air is combined with test aerosol, where the median diameter aligns with the particle size at the minimum efficiency point of the sheet filter medium, known as the Most Penetrating Particle Size (MPPS), with a deviation of ± 10% (refer to section 6.3).
Particle concentrations are assessed on both the upstream and downstream sides using either two parallel counters or a single counter that alternates between measurements It is essential to select the upstream particle number concentration and measurement duration to ensure that the difference between the counted and minimum particle number does not exceed 5% of the measured value, which should be at least 1.5 x 10³ particles For the downstream side, the difference between the maximum particle number and the counted value must not deviate by more than 20% from the measured number, corresponding to a minimum of 100 particles.
When choosing the measurement duration, care shall be taken that the test filter is not overburdened with aerosol.
Testing with a polydisperse test aerosol
The testing is done according to 8.4.2 using a polydisperse aerosol the median diameter of which shall not deviate from the MPPS by more than 50 % (see 6.3)
When testing with a polydisperse test aerosol, optical particle counters are used to measure both the number distribution concentration and the number concentration To assess efficiency, the upstream and downstream number concentrations are collected across all size classes that fall entirely or partially within the range of MPPS/1.5 to MPPS x 1.5.
The penetration P or the efficiency E is usually given as a percentage and calculated in the following way: c
N u is the number of particles counted upstream;
N d is the number of particles counted downstream; k D is the dilution factor; c N, u is the number concentration upstream; c N, d is the number concentration downstream;
V & s,u is the sampling volume flow rate upstream;
V & s,d is the sampling volume flow rate downstream; t u is the sampling duration upstream; t d is the sampling duration downstream
To determine the minimum efficiency E 95%,min, the less favorable limit value for the 95% confidence range of the actual particle count must be utilized Calculations should adhere to the particle counting statistics outlined in Clause 7 of EN 1822-2:2009 It is essential that the values for the 95% confidence range are derived solely from pure counting data, without any adjustments for the dilution factor.
Nu, 95%min = Nu - 1.96 × Nu 1/2 (6) c N, u, 95%min u u s,
E 95%min is the minimum efficiency taking into account the particle counting statistics;
N u, 95%min is the lower limit of the 95 % confidence range of the particle count upstream
N d, 95%max is the upper limit of the 95 % confidence range of the particle count downstream
(calculation according to EN 1822-2); c N, d, 95%max is the maximum downstream particle number concentration; c N, u, 95%min is the minimum upstream particle number concentration
If the manufacturer's instructions for the particle counter include coincidence corrections for the measured concentrations, then these shall be taken into account in the evaluation
For the minimum efficiency, allowance is only made for measurement uncertainty due to low count rates The minimum efficiency is the basis of the classification in accordance with EN 1822-1
Table 1 shows a specimen calculation of the statistical uncertainty for the measurement of the efficiency
The test report for the efficiency test of the filter element shall at least contain the following information: a) Test object:
1) Type designation, part number and serial number of the filter;
2) Overall dimensions of the filter;
3) Installation position of the filter (gasket upstream or downstream); b) Test parameters:
1) Temperature and relative humidity of the test air;
2) Nominal air volume flow rate and test air volume flow rate of filter;
3) Most penetrating particle size (MPPS) of filter media at corresponding medium velocity (see
4) Aerosol generator (type designation and part number);
5) Test aerosol (substance, median diameter, geometrical standard deviation);
NOTE In case a solid aerosol (e.g PSL) is used, requirements of A.5 should be met
6) Particle counter(s), upstream and downstream (type designation and part number(s)) and particle size channel(s) used (in case of OPC);
7) Dilution system for upstream particle counter (type designation, part number);
8) Sampling probe downstream side (geometry, sampling air flow);
9) Reference leak penetration and signal value setting (relevant limit value indicating a leak); c) Test results
1) Mean differential pressure across the filter at test air volume flow;
2) Mean upstream and downstream particle concentration;
3) Mean integral efficiency and minimum integral efficiency E 95%min;
4) Filter class in accordance with EN 1822-1
Table 1 — Examples of calculations of the statistical uncertainty when measuring the efficiency Constant upstream test parameters:& Vs = 23,58 cm
; tu = 50 s; dilution factorkD: 100 Filter class Test parameterE 10E 11E 12H 13H 14U 15U 16U 17 N u a, b 124 825 124 825 124 825 124 825 124 825 1 872 380 1 872 380 1 872 380 N u, 95%m in a, b 124 133 124 133 124 133 124 133 124 133 1 869 698 1 869 698 1 869 698 c Nu in c m -3 10 587 10 587 10 587 10 587 10 587 158 811 158 811 158 811 c Nu, m in in c m -3 10 529 10 529 10 529 10 529 10 529 158 583 158 583 158 583 t d in s 250 250 250 250 250 250 1 000 1 000 N d 6 241 265 1 716 348 171 635 17 163 1 716 2 575 1 030 103 N d, 95%m ax 6 246 162 1 718 916 172 447 17 420 1 798 2 674 1 093 123 c Nd in c m -3 1 059 291 29, 1 2, 91 0, 29 0, 44 0, 044 0, 0044 c Nd, m ax in c m -3 1 060 292 29, 3 2, 95 0, 30 0, 45 0, 046 0, 0052 E in % 90 97, 25 99, 725 99, 972 5 99, 997 25 99, 999 725 99, 999 972 5 99, 999 997 25 E mi n in % 89, 94 97, 23 99, 722 99, 971 9 99, 997 10 99, 999 714 99, 999 970 7 99, 999 996 70 % min % 95, in N N N u u u − 0, 55 0, 55 0, 55 0, 55 0, 55 0, 14 0, 14 0, 14 % max % 95, in N
N N d d d − 0, 08 0, 15 0, 47 1, 50 4, 78 3, 84 6, 12 19, 42 a A ct ual part ic le count w ithout al lo w ing for the di lu tion fact or. b Us ing po is son st at is tics
11 Maintenance and inspection of the test apparatus
All components and measuring instruments of the test apparatus shall be regularly maintained, inspected and calibrated
Maintenance and inspection tasks outlined in Table 2 must be performed at least once within the specified timeframes Additionally, if disturbances occur that necessitate maintenance, or following significant alterations or refurbishments, immediate inspection and, if necessary, calibration work should be conducted.
Details of the maintenance and inspection work are specified in EN 1822-2, which also contains details of the calibration of all components and measuring instruments of the test apparatus
Table 2 — Summary of the maintenance and inspection intervals of the components of the test set-up
Component Type and frequency of the maintenance/inspection
Operating materials Daily checks, exchange after use
When maximum pressure drop is reached or in the event of leaks
Aerosol generator According to manufacturers instructions and in accordance with
Pipes leading aerosol to the measuring instruments Annual cleaning or after an aerosol change
Volume flow rate meter Annually or after alterations to the instrument
Air-tightness of parts of apparatus at low pressure Check if the zero count rate of the particle counter is unsatisfactory
Air-tightness of the testing point switch valve (if present) Check annually
Purity of the test air Check weekly
Testing and classification method for filters with MPPS ≤ 0,1 àm
Background
EPA, HEPA, and ULPA filters utilizing expanded PTFE Membrane (eMembrane) filter mediums are emerging as alternatives to traditional micro fiberglass filters, particularly in critical applications like microelectronics These membrane filters possess unique properties that glass filter media lack, while maintaining a fibrous structure that allows for effective particle retention similar to that of glass fiber media However, users should be mindful of two distinct features that could influence both testing and performance in practical applications.
MPPS of filters with Membrane filter medium
The mean size of the fibrous structure in membrane filter media is significantly smaller than that of microfibre media, leading to a minimum particle penetration size (MPPS) of approximately 0.07 µm for PTFE membranes, compared to 0.1 µm to 0.25 µm for microfibreglass media Testing these filters at their MPPS, as outlined in EN 1822, necessitates the detection of particles as small as 0.05 µm, which exceeds the capabilities of standard laser particle counters Consequently, membrane filters require the use of more sensitive counters, such as CNCs, to accurately assess their performance When tested with commercially available particle generators producing 0.15 µm DEHS particles, the penetration rates observed with laser counters, which have a lower detection limit of 0.1 µm, are typically an order of magnitude lower than those measured at the MPPS Therefore, classifying these filters based on MPPS values according to EN 1822 principles is not directly feasible.
Penetration consistency and uniformity of Membrane filter medium
The membrane medium, unlike traditional micro fibreglass media, consists of a delicate mono-layer of fibrous structure, typically measuring 0.02 mm in thickness To enhance its handling, this fragile membrane is often layered onto more robust webs, which may influence filtration performance However, achieving consistent and uniform filtration properties with a mono-layer remains a challenge To address issues of spatial non-uniformity and potential leaks, some manufacturers incorporate additional layers When conducting penetration measurements on mono-layer membrane media, it is essential to account for local differences in penetration that can vary by at least two orders of magnitude.
Procedure for testing and classification of filters with Membrane filter media
Integral Penetration
Define MPPS of a flat sheet of filter medium as per EN 1822-3
To measure the integral penetration of the filter element with a membrane filter medium, follow the specified standard using DEHS aerosol at its most penetrating particle size (MPPS), which typically ranges from 0.06 µm to 0.08 µm Employ appropriate aerosol generation and detection methods, commonly utilizing Condensation Nuclei Counters (CNCs), to obtain accurate results.
NOTE 1 Particle counters used for this procedure/measurement should at least have 50 % counting efficiency at a particle size of MPPS/1,5
To be applied if the standard procedure, described above, cannot be followed due to lack of adequate measurement equipment
The Minimum Penetration Particle Size (MPPS) is defined and the penetration of a flat sheet membrane filter medium is measured at the MPPS for the air velocity corresponding to the nominal airflow of the filter element, in accordance with EN 1822-3 Additionally, penetration is measured for particles of size (0.14 ± 0.02) µm of the flat sheet filter medium as specified by EN 1822-3 A correlation factor between the two penetration values is established.
The integral penetration of the filter element with membrane filter media should be measured according to the specified standard using DEHS aerosol particles sized at (0.14 ± 0.02) µm This measurement is conducted with laser particle counters that have a lower detection limit of 0.1 µm It is important to note that for filters utilizing membrane filter media, this measurement does not represent the Most Penetrating Particle Size (MPPS).
Classification
If the integral penetration has been measured with the Standard Procedure (MPPS), classify the Membrane filter medium filters as per EN 1822-1:2009, Table 1, using the actually measured efficiency values
If the integral penetration has been measured with the Alternative Procedure (Non-MPPS), apply the correlation factor F, determined with the flat sheet measurement, to define the calculated MPPS penetration
Classify the membrane filter medium filters as per EN 1822-1:2009, Table 1, using the calculated MPPS penetration PMPPS-C.
Local Penetration
Measure the filter element using the membrane filter medium for local penetration through the scan testing method outlined in EN 1822-4 Apply the leak criteria specified in EN 1822-1:2009, Table 1, corresponding to the filter class identified in section A.4.2 The filter can be leak tested using either its true MPPS aerosol or a 0.14 µm aerosol, as the aerosol size does not significantly affect the testing results.
Publication of data and labelling of products with membrane filter media
For publication of data, test reports and labelling of products made with membrane filter media, the following rules shall apply in addition to those, mentioned in Clause 10:
1) Indicate that the filter medium is a membrane medium
2) Indicate that integral and local efficiency measurement as well as classification was made according to Annex A
The test report must clearly indicate whether the integral MPPS penetration was measured using the Standard Procedure (true MPPS) or the Alternative Procedure (Non-MPPS particle size).
EXAMPLE 1 Filter tested as per “Standard Procedure”
Penetration 99,999 98 % for MPPS as per EN 1822-5:2009, Annex A, Standard Procedure
Filter class U16 as per EN 1822-1:2009
NOTE In Example 1, efficiency and filter class have been determined as per “Standard Procedure” of Annex A, using MPPS aerosol
EXAMPLE 2 Filter tested as per “Alternative Procedure”
Efficiency 99,999 98 % for MPPS as per EN 1822-5:2009, Annex A, Alternative Procedure
Filter class U16 as per EN 1822-1:2009
Testing and classification of filters using media with (charged) synthetic fibers
Background
In recent years, synthetic fibre filter media boasting a nominal efficiency of 99.95% have emerged, primarily achieved through the use of fine-diameter fibres and the electrostatic charging of these fibres to enhance filtration properties Various commercial and patented processes for charging exist, each with distinct performance claims These advanced filters are increasingly viewed as viable alternatives to traditional High Efficiency filters that utilize glass fibre media.
Electrostatic filters, unlike actively charged electrostatic precipitators that rely on external power, experience charge dissipation over time due to neutralization by collected particles This charge loss is particularly pronounced with liquid, sub-micron, or charged particles, leading to significant variations in filter performance based on test conditions and aerosol types As these filters accumulate particles, their efficiency can deteriorate drastically, sometimes by several orders of magnitude once the charge effects are neutralized Given that EPA, HEPA, or ULPA filters are often used in critical applications and can remain in service for many years, it is essential to account for these performance declines during testing and classification.
Scope
This annex is essential for all filter media containing over 20% synthetic materials, excluding glass However, for wet laid glass fibre filter media, studies have shown that the impact of charges on glass fibres does not affect their performance, thus exempting them from this test.
Procedure for testing and classification of HEPA and ULPA filters using media with (charged) synthetic fibres
1) Flat sheet filter medium MPPS penetration tests should be performed as per EN 1822-3 with a statistically sufficient number of flat sheet filter medium samples, in new, possibly charged condition
After testing the flat sheet filter medium samples in a new, potentially charged state, they must be discharged according to the procedure outlined in Annex A of EN 779:2002 Alternative discharging methods may be utilized, provided it can be demonstrated that they achieve the same level of discharge as the EN 779:2002, Annex A procedure.
3) Flat sheet filter medium MPPS penetration tests as per EN 1822-3 should now be repeated with the discharged flat sheet filter medium samples
The penetration and classification of the filter element utilizing charged synthetic fiber filter media should be documented based on the average measurement values obtained from discharged flat sheet filter medium samples This is applicable when the penetration in the discharged condition exceeds twice that of the charged condition.
Publication of data and labelling of products for HEPA and ULPA filters using media
If the penetration in a discharged state exceeds twice that of the charged state, additional rules will apply, alongside those specified in Clause 10, regarding the publication of data and labeling of products made with (charged) synthetic fibers.
1) Indicate that the filter medium contains charged synthetic fibres as per Annex B of EN 1822-5:2009
2) The MPPS penetration must be shown on all relevant documents and labels as the value(s) measured in fully discharged condition of the filter medium as per Annex B of EN 1822-5:2009
3) The filter classification must be determined and indicated on all relevant documents and labels on the bases of penetration values, measured in fully discharged condition of the filter medium
The MPPS efficiency of a filter medium in its new, charged condition can be specified for informational purposes, provided it is clearly noted that this value applies solely to the new state of the filter This efficiency value can be obtained either through measurements conducted on the complete filter unit according to the relevant standard or by averaging the measurements from five flat sheet filter medium samples.
Efficiency 99,98 % for MPPS in discharged condition as per Annex B of EN 1822-5:2009
Filter class H12 as per EN 1822-1:2009 and Annex B, EN 1822-5:2009
NOTE 1 In Example 1, efficiency and classification are given for discharged condition only
Efficiency 99,98 % for MPPS in discharged condition as per Annex B of EN 1822-5:2009
Efficiency 99,998 % for MPPS in new, charged condition as per Annex B of EN 1822-5:2009
Filter class H12 as per EN 1822-1:2009 and Annex B, EN 1822-5:2009
NOTE 2 In Example 2 efficiency is given for discharged AND charged conditon but classification, according to
EN 1822-1 and Annex B of this standard, is always and only given for discharged condition
[1] EN ISO 9000, Quality management systems — Fundamentals and vocabulary (ISO 9000:2005)
[2] ISO 2859-1, Sampling procedures for inspection by attributes — Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection