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Bulk chemicals and petrochemicals: Air filter testing
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Feature
Filtration+Separation October 2007
Bulk chemicals and petrochemicals:
Air filter testing W
hen working with gases and oils, air filters play the important role of stopping unwanted charges into air and protecting expensive industrial systems from damage – and at some point the filters will need testing. Richard Wakeman explains all. Like most other process equipment, filters have developed to improve their in-service performance, for example reduced pressure losses or improved particle retention through more advanced filter media utilising various treatments to filter fibres or the application of nanofibres. The performance of an air filter is generally evaluated on four parameters:
Introduction Air filters are generally simple in concept yet they are technically complicated devices. The filter helps to mitigate the health effects of such air pollutants by improving the quality of air or preventing unwanted discharges into air, or protects air handling equipment or costly systems like gas turbine compressors. The contaminants are numerous and an air filter is the primary defence measure against airborne solid particles such as grit (particle sizes >76 µm) and dust which includes particles such as minerals and pollen (sizes <76 µm), smoke (<4 µm), fume (<1 µm), and liquid aerosols that arise in mists (<10 µm) and fogs (>10 µm).
• Contaminant removal efficiency – tested by challenging the filter with contaminant on the upstream side and measuring the contaminant that passes through the filter to its downstream side. • Contaminant holding capacity – determined by measuring the mass
Table 1: Classification of air filters according to EN 779 and EN 1822 Class
Final pressure drop (Pa)
Average arrestance (Am) of synthetic dust (%) 50 65 80 90
G1 G2 G3 G4
Primary filters to collect coarse dust (EN 779)
250 250 250 250
F5 F6 F7 F8 F9
Secondary filters to collect and retain finer dust (EN 779)
450 450 450 450 450
H10 H11 H12 H13 H14
Tertiary filters for specific particulate control – HEPA type (EN 1822)
U15 U16 U17
High efficiency air filters – ULPA type (EN 1822)
= = = =
Average efficiency (Em) of 0.4 µm (%)
Am < 65 Am < 80 Am < 90 Am 40 60 80 90 95
= = = = =
Em Em Em Em Em
< < < <
60 80 90 95
Local collection efficiency of MPPS (%)
Average (integral) collection efficiency of MPPS (%)
99.75 99.975
85 95 99.5 99.95 99.995
99.9975 99.99975 99.9999
99.9995 99.99995 99.999995
of contaminant retained by the filter when it reaches its maximum allowable differential pressure. • Resistance to airflow – determined by measuring the pressure of the air upstream and downstream of the filter. The value of resistance to airflow should be accompanied by the value of air velocity in order to understand the performance of the filter. • Safety, particularly with reference to the ability of the filter to support or spread a fire when there is no other fuel source, or release sparks when exposed to a flame, or to generate smoke.
Contaminants are numerous and an air filter is the primary defence measure against airborne solid particles. There are many standards that relate to either the testing or application of air filters; this article presents only those that can be used to compare air cleaners on a standardised basis irrespective of their application.
Air filter testing Many air filter testing methods have been developed for predicting and comparing the performance of filters of differing designs; organisations involved in setting filter standards include the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE), the European Committee for Standardisation (CEN), the International Standards Organization (ISO), and Underwriters Laboratories (UL). Although the purpose and focus of these organisations differs there is overlap of their standards and testing methods. A widely accepted test for primary and secondary filters, mainly panel and pocket
Feature
Filtration+Separation October 2007
media type filters, is based on the ASHRAE 52 standard which was adopted in the UK (BS 6540) and other European countries (EUROVENT 4/5); the European Community later adopted the standards as EN 779. The terms ‘efficiency’ and ‘penetration’ are often referred to when reporting results from air filter tests, and are related by
A further term, ‘arrestance’ is often used to describe a filter’s ability to capture and retain dust and is defined as the mass removal of loading dust; the average arrestance is the ratio of the total amount of loading dust retained by the filter to the total amount of dust fed up to the final pressure drop.
EN 779 – particulate filter testing Guidance to testing primary and secondary filters is given in EN 779. More strictly, EN 779 is applicable to air filters having an initial efficiency of <98% with respect to 0.4 µm particles when tested at an air flow rate between 850 and 5400 m3 h-1. The tests are based on measuring the effect of challenging a test filter with two synthetic aerosols. Efficiency of finer Class F filters, is measured using a fine synthetic dust, DEHS
(DiEthylHexylSebacate), produced by a generator capable of producing sufficient particles in the 0.2 to 3.0 µm size range. A coarser dust which is composed mainly of Arizona road dust (ISO 12103-1) is used to obtain information about dust holding capacity and, in the case of coarser Class G filters, filtration efficiency with respect to coarse loading dust (arrestance).
The revised EN 779:2002 provided better knowledge about the performance of filters than previous standards and made it possible to evaluate filter performance properties in relation to indoor air quality requirements and process demands. EN 779 grades filters according to their efficiency (arrestance) under a defined set of test conditions – an air flow rate of 3400 m3 h-1 and a maximum pressure drop of 250 kPa for coarse (Class G) filters, or 450 kPa for fine (Class F) filters. The relationship between filter class and efficiency or arrestance is shown in Table 1. The efficiency of air filters is measured through a sequence of tests that use dust to load the filter to accelerate what would otherwise be a very length test, and in this way aims to simulate the filter in service. The
principle for the test procedure is that filter efficiency increases with dust loading; filters with average efficiencies of less than 20% or greater than 98% are unsuitable for this test. The revised EN 779:2002 provided better knowledge about the performance of filters than previous standards and made it possible to evaluate filter performance properties in relation to Indoor Air Quality (IAQ) requirements and process demands, and offered improved agreement between laboratory test results and actual installations, as well as giving a faster, simpler method that is easier to understand.
EN 1822 – high efficiency filter testing The European standardisation body introduced EN 1822 for the classification and testing of HEPA (High Efficiency Particulate Air) and ULPA (Ultra Low Penetration Air) filters, based on filter efficiency at the most penetrating particle size (MPPS). In many applications the integrity and suitability of HEPA/ULPA filters is evaluated in their installed condition. In-situ testing is performed in, for example, the microelectronics and food industries to ensure the final product quality, whilst in the pharmaceutical industry it is mandatory to protect humans against health hazards. Testing according to EN 1822 is normally performed with the filter in its new condition,
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Filtration+Separation October 2007
Table 2: Minimum efficiency reporting value parameters defined in ASHRAE 52.2 (an empty box in the table indicates that the box is not applicable). MERV
Composite average particle size efficiency (% in size range)
Range 1 0.3 to 1 µm
Range 2 1.0 to 3.0 µm
Average arrestance (%) using ASHRAE 52.1
Minimum final resistance Pa
Range 3 3.0 to 10.0 µm
1
E3 < 20
Aavg < 65
75
2
E3 < 20
65 = Aavg < 70
75
3
E3 < 20
70 = Aavg < 75
75
4
E3 < 20
75 = Aavg
75
5
20 = E3 < 35
150
6
35 = E3 < 50
150
7
50 = E3 < 70
150
8
70 = E3
150
9
E2 < 50
85 = E3
250
10
50 = E2 < 65
85 = E3
250
11
65 = E2 < 80
85 = E3
250
12
80 = E2
90 = E3
250
13
E1 < 75
90 = E2
90 = E3
350
14
75 = E1 < 85
90 = E2
90 = E3
350
15
85 = E1 < 95
90 = E2
90 = E3
350
16
95 = E1
95 = E2
95 = E3
350
using an aerosol probe that can be moved over the entire surface of the filter. This moving or scanning of the aerosol probe results in the measurement of many local collection efficiencies. These local efficiencies can be used to calculate the overall efficiency of the filter or the ‘leak rate’ of a specific area of the filter. The overall efficiency calculation is also known as the integral value, while the leak rate is termed the local value. The most important measurements using EN 1822 are: • Pressure drop at a nominal volumetric flow; • Overall (integral) particle collection efficiency for the particle size with the greatest penetration (MPPS) at the nominal volumetric flow; • Local collection efficiencies for the MPPS at the nominal volumetric flow; • Freedom from leaks in Class H13 and upwards. The results are used for allocation of a filter to a class designated between H10 and U17 (as indicated in Table 1). Determination of the collection efficiency and the MPPS can be difficult, so for Classes H13 and H14 the standard permits evaluation for freedom from leaks by use of the oil thread test, in which case the filter is not scanned.
ASHRAE 52.2 This standard assesses the ability of a filter to remove particles from an air stream and
its resistance to the airflow. The loading dust is a mixture of SAE Standard J726 fine dust, powdered carbon and milled cotton linters. The test procedure uses laboratory generated potassium chloride particles in the size range 0.3 to 10 µm dispersed in air as the test aerosol, and a particle counter to count the particles in twelve size ranges. Particle counts are taken both upstream and downstream of the filter to determine its efficiency.
The separation challenge imposed on an air filter is dependent on the nature of the dust in the incoming air or gas stream, and in the case of HVAC applications the challenge changes with the environment inside and outside of the building. The test results enable a MERV (Minimum Efficiency Reporting Value) to be ascribed to the filter. The range of MERV parameters is shown in Table 2, from which it is seen that the MERV defines a specific range of parameters that the filter is able to meet. By way of example, a filter that has an E3 efficiency of between 50 and 70% would have a MERV of 7; a filter that has an E1 efficiency of between 85 and 95% would have a MERV of 15. A filter must also be operated with a minimum final pressure drop that is consistent with the reporting value in Table 2.
Dust holding capacity is not a parameter considered in ASHRAE 52.2, and it is not possible to estimate service life from the test results. However, a user can select a filter based on the size of the contaminant particles in the air stream, including respirable size dusts. ASHRAE 52.1 and 52.2 are under review, with a proposal to creating a single ASHRAE test standard for determining the efficiency of HVAC filters. This would reduce the number of tests needed on a filter and allow a single test rig to perform all the required tests. As part of this updating, it is proposed that the dust spot efficiency test requirements is removed since the particle size efficiency used in 52.2 provides more direct and useful data.
Air filter safety The characteristics, components and materials used in HEPA filters in relation to risk of fire or electric shock or injury to people are covered by UL 586, which defines minimum constructional requirements along with a minimum criterion flame test. The combustibility and amount of smoke generated by air filter units of both washable and throwaway types in their clean condition are covered in UL 900. The UL 900 test simulates a fire that impinges on the filter within a duct. The test filter, mounted inside a standard size duct with a specific airflow through it. The test is started when a methane flame is ignited upwind of the filter,
Feature
Filtration+Separation October 2007
resulting in flame impingement on the filter. For classification, limits are placed on the amount of smoke and flames that may pass through the filter: • Class 1: no flames or sparks may pass through the filter and only a small amount of smoke is generated; • Class 2: limited flaming and sparking are acceptable and a larger amount of smoke may be generated.
Conclusions Filter efficiency, dust holding capacity and differential pressure generally provide the basic measures used to assess a filter’s efficiency, and each can be measured in a variety of ways, although to conform to a standard each must be measured in accordance with the recommendations in the standard. The performance of an air filter changes over time, and the efficiency tends to increase as the filter becomes loaded with dust. The separation challenge imposed on an air filter is dependent on the nature of the dust in the incoming air or gas stream, and in the case of HVAC applications the challenge changes with the environment inside and outside of the building. The application of an air filter relates to the environment in which the filter is to be used. Hence standards for, for
example, indoor air quality (e.g. EN 13779), air quality in controlled environments such as clean rooms (e.g. ISO 14644-1), or cabin air (e.g. DIN 71460) may need to be consulted. Most air filters are installed in a system for many months or sometimes years before they are replaced; yet testing of the filters occurs within a matter of hours. In service, an air filter will experience many environmental changes such as temperature, humidity, airflow velocity, and dust particle load; but its original testing was done in a controlled environment. The imperfections of testing methodologies and the varied motivations of the people developing test methods have to be recognised, from which it should be concluded that it is important to fully understand how to interpret the results of any air filter test prior to using the results to make important decisions.
•
Contact: Richard Wakeman Consultant Engineer and Professor of Chemical Engineering 5 Henry Dane Way, Newbold, Leicestershire, LE67 8PP United Kingdom www.richardwakeman.co.uk
Bibliography ASHRAE 52.1: 1992. Gravimetric and Dust Spot Procedures for Testing Air Cleaning
Devices Used in General Ventilation for Removing Particulate Matter. ASHRAE 52.2: 1999. Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size. DIN 71460: 2006. Air Filters for Passenger Compartments. EN 779: 2002. Particulate Air Filters for General Ventilation – Determination of the Filtration Performance. EN 13779: 2005. Ventilation for NonResidential Buildings – Performance Requirements for Ventilation and Room Conditioning Systems. EN 1822: 1998/2001. High Efficiency Air Filters (HEPA and ULPA) Parts 1-5. ISO 12103-1: 1997. Road vehicles – Test Dust for Filter Evaluation – Part 1: Arizona Test Dust. ISO 14644-1: 1999-2006. Cleanrooms and Associated Controlled Environments, Parts 1-8. SAE Standard J726: 1993. Air Cleaner Test Code. UL 586: 1991. High-Efficiency, Particulate, Air Filter Units. UL 900: 2004. Air Filter Units.
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Feature
Filtration+Separation October 2007
Bulk chemicals and petrochemicals:
Air filter testing W
hen working with gases and oils, air filters play the important role of stopping unwanted charges into air and protecting expensive industrial systems from damage – and at some point the filters will need testing. Richard Wakeman explains all. Like most other process equipment, filters have developed to improve their in-service performance, for example reduced pressure losses or improved particle retention through more advanced filter media utilising various treatments to filter fibres or the application of nanofibres. The performance of an air filter is generally evaluated on four parameters:
Introduction Air filters are generally simple in concept yet they are technically complicated devices. The filter helps to mitigate the health effects of such air pollutants by improving the quality of air or preventing unwanted discharges into air, or protects air handling equipment or costly systems like gas turbine compressors. The contaminants are numerous and an air filter is the primary defence measure against airborne solid particles such as grit (particle sizes >76 µm) and dust which includes particles such as minerals and pollen (sizes <76 µm), smoke (<4 µm), fume (<1 µm), and liquid aerosols that arise in mists (<10 µm) and fogs (>10 µm).
• Contaminant removal efficiency – tested by challenging the filter with contaminant on the upstream side and measuring the contaminant that passes through the filter to its downstream side. • Contaminant holding capacity – determined by measuring the mass
Table 1: Classification of air filters according to EN 779 and EN 1822 Class
Final pressure drop (Pa)
Average arrestance (Am) of synthetic dust (%) 50 65 80 90
G1 G2 G3 G4
Primary filters to collect coarse dust (EN 779)
250 250 250 250
F5 F6 F7 F8 F9
Secondary filters to collect and retain finer dust (EN 779)
450 450 450 450 450
H10 H11 H12 H13 H14
Tertiary filters for specific particulate control – HEPA type (EN 1822)
U15 U16 U17
High efficiency air filters – ULPA type (EN 1822)
= = = =
Average efficiency (Em) of 0.4 µm (%)
Am < 65 Am < 80 Am < 90 Am 40 60 80 90 95
= = = = =
Em Em Em Em Em
< < < <
60 80 90 95
Local collection efficiency of MPPS (%)
Average (integral) collection efficiency of MPPS (%)
99.75 99.975
85 95 99.5 99.95 99.995
99.9975 99.99975 99.9999
99.9995 99.99995 99.999995
of contaminant retained by the filter when it reaches its maximum allowable differential pressure. • Resistance to airflow – determined by measuring the pressure of the air upstream and downstream of the filter. The value of resistance to airflow should be accompanied by the value of air velocity in order to understand the performance of the filter. • Safety, particularly with reference to the ability of the filter to support or spread a fire when there is no other fuel source, or release sparks when exposed to a flame, or to generate smoke.
Contaminants are numerous and an air filter is the primary defence measure against airborne solid particles. There are many standards that relate to either the testing or application of air filters; this article presents only those that can be used to compare air cleaners on a standardised basis irrespective of their application.
Air filter testing Many air filter testing methods have been developed for predicting and comparing the performance of filters of differing designs; organisations involved in setting filter standards include the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE), the European Committee for Standardisation (CEN), the International Standards Organization (ISO), and Underwriters Laboratories (UL). Although the purpose and focus of these organisations differs there is overlap of their standards and testing methods. A widely accepted test for primary and secondary filters, mainly panel and pocket
Feature
Filtration+Separation October 2007
media type filters, is based on the ASHRAE 52 standard which was adopted in the UK (BS 6540) and other European countries (EUROVENT 4/5); the European Community later adopted the standards as EN 779. The terms ‘efficiency’ and ‘penetration’ are often referred to when reporting results from air filter tests, and are related by
A further term, ‘arrestance’ is often used to describe a filter’s ability to capture and retain dust and is defined as the mass removal of loading dust; the average arrestance is the ratio of the total amount of loading dust retained by the filter to the total amount of dust fed up to the final pressure drop.
EN 779 – particulate filter testing Guidance to testing primary and secondary filters is given in EN 779. More strictly, EN 779 is applicable to air filters having an initial efficiency of <98% with respect to 0.4 µm particles when tested at an air flow rate between 850 and 5400 m3 h-1. The tests are based on measuring the effect of challenging a test filter with two synthetic aerosols. Efficiency of finer Class F filters, is measured using a fine synthetic dust, DEHS
(DiEthylHexylSebacate), produced by a generator capable of producing sufficient particles in the 0.2 to 3.0 µm size range. A coarser dust which is composed mainly of Arizona road dust (ISO 12103-1) is used to obtain information about dust holding capacity and, in the case of coarser Class G filters, filtration efficiency with respect to coarse loading dust (arrestance).
The revised EN 779:2002 provided better knowledge about the performance of filters than previous standards and made it possible to evaluate filter performance properties in relation to indoor air quality requirements and process demands. EN 779 grades filters according to their efficiency (arrestance) under a defined set of test conditions – an air flow rate of 3400 m3 h-1 and a maximum pressure drop of 250 kPa for coarse (Class G) filters, or 450 kPa for fine (Class F) filters. The relationship between filter class and efficiency or arrestance is shown in Table 1. The efficiency of air filters is measured through a sequence of tests that use dust to load the filter to accelerate what would otherwise be a very length test, and in this way aims to simulate the filter in service. The
principle for the test procedure is that filter efficiency increases with dust loading; filters with average efficiencies of less than 20% or greater than 98% are unsuitable for this test. The revised EN 779:2002 provided better knowledge about the performance of filters than previous standards and made it possible to evaluate filter performance properties in relation to Indoor Air Quality (IAQ) requirements and process demands, and offered improved agreement between laboratory test results and actual installations, as well as giving a faster, simpler method that is easier to understand.
EN 1822 – high efficiency filter testing The European standardisation body introduced EN 1822 for the classification and testing of HEPA (High Efficiency Particulate Air) and ULPA (Ultra Low Penetration Air) filters, based on filter efficiency at the most penetrating particle size (MPPS). In many applications the integrity and suitability of HEPA/ULPA filters is evaluated in their installed condition. In-situ testing is performed in, for example, the microelectronics and food industries to ensure the final product quality, whilst in the pharmaceutical industry it is mandatory to protect humans against health hazards. Testing according to EN 1822 is normally performed with the filter in its new condition,
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Filtration+Separation October 2007
Table 2: Minimum efficiency reporting value parameters defined in ASHRAE 52.2 (an empty box in the table indicates that the box is not applicable). MERV
Composite average particle size efficiency (% in size range)
Range 1 0.3 to 1 µm
Range 2 1.0 to 3.0 µm
Average arrestance (%) using ASHRAE 52.1
Minimum final resistance Pa
Range 3 3.0 to 10.0 µm
1
E3 < 20
Aavg < 65
75
2
E3 < 20
65 = Aavg < 70
75
3
E3 < 20
70 = Aavg < 75
75
4
E3 < 20
75 = Aavg
75
5
20 = E3 < 35
150
6
35 = E3 < 50
150
7
50 = E3 < 70
150
8
70 = E3
150
9
E2 < 50
85 = E3
250
10
50 = E2 < 65
85 = E3
250
11
65 = E2 < 80
85 = E3
250
12
80 = E2
90 = E3
250
13
E1 < 75
90 = E2
90 = E3
350
14
75 = E1 < 85
90 = E2
90 = E3
350
15
85 = E1 < 95
90 = E2
90 = E3
350
16
95 = E1
95 = E2
95 = E3
350
using an aerosol probe that can be moved over the entire surface of the filter. This moving or scanning of the aerosol probe results in the measurement of many local collection efficiencies. These local efficiencies can be used to calculate the overall efficiency of the filter or the ‘leak rate’ of a specific area of the filter. The overall efficiency calculation is also known as the integral value, while the leak rate is termed the local value. The most important measurements using EN 1822 are: • Pressure drop at a nominal volumetric flow; • Overall (integral) particle collection efficiency for the particle size with the greatest penetration (MPPS) at the nominal volumetric flow; • Local collection efficiencies for the MPPS at the nominal volumetric flow; • Freedom from leaks in Class H13 and upwards. The results are used for allocation of a filter to a class designated between H10 and U17 (as indicated in Table 1). Determination of the collection efficiency and the MPPS can be difficult, so for Classes H13 and H14 the standard permits evaluation for freedom from leaks by use of the oil thread test, in which case the filter is not scanned.
ASHRAE 52.2 This standard assesses the ability of a filter to remove particles from an air stream and
its resistance to the airflow. The loading dust is a mixture of SAE Standard J726 fine dust, powdered carbon and milled cotton linters. The test procedure uses laboratory generated potassium chloride particles in the size range 0.3 to 10 µm dispersed in air as the test aerosol, and a particle counter to count the particles in twelve size ranges. Particle counts are taken both upstream and downstream of the filter to determine its efficiency.
The separation challenge imposed on an air filter is dependent on the nature of the dust in the incoming air or gas stream, and in the case of HVAC applications the challenge changes with the environment inside and outside of the building. The test results enable a MERV (Minimum Efficiency Reporting Value) to be ascribed to the filter. The range of MERV parameters is shown in Table 2, from which it is seen that the MERV defines a specific range of parameters that the filter is able to meet. By way of example, a filter that has an E3 efficiency of between 50 and 70% would have a MERV of 7; a filter that has an E1 efficiency of between 85 and 95% would have a MERV of 15. A filter must also be operated with a minimum final pressure drop that is consistent with the reporting value in Table 2.
Dust holding capacity is not a parameter considered in ASHRAE 52.2, and it is not possible to estimate service life from the test results. However, a user can select a filter based on the size of the contaminant particles in the air stream, including respirable size dusts. ASHRAE 52.1 and 52.2 are under review, with a proposal to creating a single ASHRAE test standard for determining the efficiency of HVAC filters. This would reduce the number of tests needed on a filter and allow a single test rig to perform all the required tests. As part of this updating, it is proposed that the dust spot efficiency test requirements is removed since the particle size efficiency used in 52.2 provides more direct and useful data.
Air filter safety The characteristics, components and materials used in HEPA filters in relation to risk of fire or electric shock or injury to people are covered by UL 586, which defines minimum constructional requirements along with a minimum criterion flame test. The combustibility and amount of smoke generated by air filter units of both washable and throwaway types in their clean condition are covered in UL 900. The UL 900 test simulates a fire that impinges on the filter within a duct. The test filter, mounted inside a standard size duct with a specific airflow through it. The test is started when a methane flame is ignited upwind of the filter,
Feature
Filtration+Separation October 2007
resulting in flame impingement on the filter. For classification, limits are placed on the amount of smoke and flames that may pass through the filter: • Class 1: no flames or sparks may pass through the filter and only a small amount of smoke is generated; • Class 2: limited flaming and sparking are acceptable and a larger amount of smoke may be generated.
Conclusions Filter efficiency, dust holding capacity and differential pressure generally provide the basic measures used to assess a filter’s efficiency, and each can be measured in a variety of ways, although to conform to a standard each must be measured in accordance with the recommendations in the standard. The performance of an air filter changes over time, and the efficiency tends to increase as the filter becomes loaded with dust. The separation challenge imposed on an air filter is dependent on the nature of the dust in the incoming air or gas stream, and in the case of HVAC applications the challenge changes with the environment inside and outside of the building. The application of an air filter relates to the environment in which the filter is to be used. Hence standards for, for
example, indoor air quality (e.g. EN 13779), air quality in controlled environments such as clean rooms (e.g. ISO 14644-1), or cabin air (e.g. DIN 71460) may need to be consulted. Most air filters are installed in a system for many months or sometimes years before they are replaced; yet testing of the filters occurs within a matter of hours. In service, an air filter will experience many environmental changes such as temperature, humidity, airflow velocity, and dust particle load; but its original testing was done in a controlled environment. The imperfections of testing methodologies and the varied motivations of the people developing test methods have to be recognised, from which it should be concluded that it is important to fully understand how to interpret the results of any air filter test prior to using the results to make important decisions.
•
Contact: Richard Wakeman Consultant Engineer and Professor of Chemical Engineering 5 Henry Dane Way, Newbold, Leicestershire, LE67 8PP United Kingdom www.richardwakeman.co.uk
Bibliography ASHRAE 52.1: 1992. Gravimetric and Dust Spot Procedures for Testing Air Cleaning
Devices Used in General Ventilation for Removing Particulate Matter. ASHRAE 52.2: 1999. Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size. DIN 71460: 2006. Air Filters for Passenger Compartments. EN 779: 2002. Particulate Air Filters for General Ventilation – Determination of the Filtration Performance. EN 13779: 2005. Ventilation for NonResidential Buildings – Performance Requirements for Ventilation and Room Conditioning Systems. EN 1822: 1998/2001. High Efficiency Air Filters (HEPA and ULPA) Parts 1-5. ISO 12103-1: 1997. Road vehicles – Test Dust for Filter Evaluation – Part 1: Arizona Test Dust. ISO 14644-1: 1999-2006. Cleanrooms and Associated Controlled Environments, Parts 1-8. SAE Standard J726: 1993. Air Cleaner Test Code. UL 586: 1991. High-Efficiency, Particulate, Air Filter Units. UL 900: 2004. Air Filter Units.
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