SIST EN 1886:2008
(Main)Ventilation for buildings - Air handling units - Mechanical performance
Ventilation for buildings - Air handling units - Mechanical performance
This standard specifies test methods, test requirements and classifications for air handling units, which are supplying and/or extracting air via a ductwork ventilating/conditioning a part or the whole of the building. This standard is not applicable to the following:
a) air conditioning units serving a limited area in a building, such as fan coil units;
b) units for residential buildings;
c) units producing ventilation air mainly for a manufacturing process.
Except for the thermal and acoustic performance of the casing, the test methods and requirements are applicable to both complete units and any separate sections.
The filter bypass test is not applicable to the testing of high efficiency particulate air filters (HEPA).
NOTE HEPA filters are recommended to be installed downstream of the air handling unit. Such installations should be leak tested in accordance with the appropriate filter standards.
The test method for the thermal performance of the casing is applicable to the comparison of different constructions, but not to the calculation of thermal losses through casing or the risk of condensation.
Similarly, the test method for the acoustic performance of the casing is applicable to the comparison of different constructions, but not to the provision of accurate acoustic data for specific units.
Lüftung von Gebäuden - Zentrale raumlufttechnische Geräte - Mechanische Eigenschaften und Messverfahren
Diese Norm legt Prüfverfahren, Prüfanforderungen und Klassifikationen für zentrale raumlufttechnische Geräte (zentrale RLT-Geräte) fest, die zum Zweck der Lüftung oder Klimatisierung eines Gebäudes oder Teilen davon Zu- und/oder Abluft durch Kanäle befördern. Diese Norm gilt nicht für:
a) Raumlufttechnische Geräte, die nur einen begrenzten Bereich in einem Gebäude versorgen, wie Ventilatorkonvektoren usw.;
b) Geräte zur Wohnungslüftung;
c) Geräte, die Zuluft überwiegend zu Produktionszwecken liefern.
Die Prüfverfahren und -anforderungen, ausgenommen die für die thermischen und akustischen Leistungen des Gehäuses, sind sowohl für komplette Baueinheit als auch für die einzelnen Einheiten gültig.
Die Filter-Bypass-Prüfung kann nicht verwendet werden, um Schwebstofffilter (HEPA-Filter) zu prüfen.
ANMERKUNG Es wird empfohlen, Schwebstofffilter nur auf der Abströmseite des zentralen raumlufttechnischen Gerätes zu installieren. Solche Installationen sollten nach entsprechenden Normen für Filter leckgetestet werden.
Das Prüfverfahren für die thermische Leistung des Gehäuses darf für den Vergleich verschiedener Konstruktionen verwendet werden, jedoch nicht, um Wärmeverluste durch das Gehäuse oder das Risiko der Kondensation zu berechnen.
Ebenso darf das Prüfverfahren für die akustische Leistung des Gehäuses nur verwendet werden, um verschiedene Produkte zu vergleichen, aber nicht, um genaue akustische Daten für bestimmte Geräteeinheiten herzuleiten.
Ventilation des bâtiments - Caissons de traitement d'air - Performances mécaniques
La présente norme spécifie les méthodes d'essai, les exigences d'essai et les classifications applicables aux
caissons de traitement d'air qui fournissent et/ou évacuent l'air par des réseaux de conduits, pour la
ventilation/climatisation de tout ou partie de bâtiment. Elle ne s’applique pas aux équipements suivants :
a) caissons de climatisation desservant une aire limitée d'un bâtiment comme les serpentins de
ventilateurs ;
b) caissons pour immeubles résidentiels ;
c) caissons produisant de l'air de ventilation principalement pour un procédé de fabrication.
Excepté en ce qui concerne les performances thermiques et acoustiques de l'enveloppe, les méthodes
d'essai et les exigences s'appliquent à la fois au caisson complet et aux différentes sections.
L'essai de dérivation du filtre ne s’applique pas aux filtres à air à très haute efficacité (HEPA).
NOTE Il est recommandé d'installer les filtres HEPA en aval du caisson de traitement d’air. Il convient que ce type
d’installations soit soumis à un essai de fuite conformément aux normes pertinentes relatives aux filtres.
La méthode d'essai des performances thermiques de l'enveloppe peut être utilisée pour comparer différentes
constructions, mais pas pour calculer les pertes thermiques à travers l'enveloppe, ni le risque de
condensation.
De même, la méthode d'essai des performances acoustiques de l'enveloppe peut être utilisée pour comparer
différentes constructions, mais pas pour fournir des données acoustiques précises pour des caissons
spécifiques.
Prezračevanje stavb - Centralne enote - Mehanske lastnosti in merilni postopki
General Information
Relations
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Ventilation for buildings - Air handling units - Mechanical performanceVentilation des bâtiments - Caissons de traitement d'air - Performances mécaniquesLüftung von Gebäuden - Zentrale raumlufttechnische Geräte - Mechanische Eigenschaften und MessverfahrenTa slovenski standard je istoveten z:EN 1886:2007SIST EN 1886:2008en,fr,de91.140.30ICS:SIST EN 1886:19991DGRPHãþDSLOVENSKI
STANDARDSIST EN 1886:200801-april-2008
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 1886December 2007ICS 91.140.30Supersedes EN 1886:1998
English VersionVentilation for buildings - Air handling units - MechanicalperformanceVentilation des bâtiments - Caissons de traitement d'air -Performances mécaniquesLüftung von Gebäuden - Zentrale raumlufttechnischeGeräte - Mechanische Eigenschaften und MessverfahrenThis European Standard was approved by CEN on 26 July 2006.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2007 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 1886:2007: E
EN 1886:2007 (E) 2 Contents Page Foreword.4 Introduction.6 1 Scope.7 2 Normative references.7 3 Terms and definitions.8 4 Usage of real units and/or model boxes for the verification of mechanical performances.8 5 Mechanical strength of casing.9 5.1 Requirements and classification.9 5.2 Testing.12 6 Casing air leakage.13 6.1 Requirements and classification.13 6.1.1 Units operating under negative pressure only.13 6.1.2 Units operating under both negative and positive pressure.14 6.2 Testing.14 6.2.1 Test apparatus.14 6.2.2 Preparation for test.15 6.3 Test procedure.16 6.4 Determination of allowable leakage rates.16 7 Filter bypass leakage.16 7.1 Requirements.16 7.1.1 General.16 7.1.2 Acceptable filter bypass leakage rates.16 7.1.3 Two or more filter sections in the same unit.17 7.2 Testing.17 7.2.1 General.17 7.2.2 Filters downstream of the fan (positive pressure).19 7.2.3 Filters upstream of the fan (negative pressure).21 8 Thermal performance of casing.23 8.1 General.23 8.2 Requirements and classification.23 8.2.1 Thermal transmittance.23 8.2.2 Thermal bridging.24 8.3 Testing.25 8.3.1 General.25 8.3.2 Test facility.25 8.3.3 Testing procedure.27 8.3.4 Evaluation of the test results.28 9 Acoustic insulation of casing.28 9.1 General.28 9.2 Test requirements.28 9.3 Test method.28 9.4 Test procedure.29 9.5 Evaluation of the sound insertion loss Dp.29 10 Fire protection.30 10.1 General.30
EN 1886:2007 (E) 3 10.2 Material.30 10.3 Sealings for air handling units.30 10.4 Locally limited and small construction parts of air handling units.31 10.5 Air heaters.31 10.6 Filters, contact humidifiers and droplet eliminators of AHU's.31 10.7 Heat recovery.31 11 Mechanical safety.31 Annex A (informative) Arrangement and requirements for circulating fans.33 Bibliography.35
EN 1886:2007 (E) 4 Foreword This document (EN 1886:2007) has been prepared by Technical Committee CEN/TC 156 “Ventilation for buildings”, the secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 2008, and conflicting national standards shall be withdrawn at the latest by June 2008. This document supersedes EN 1886:1998. The standard is a part of a series of standards for air handling units used for ventilation and air conditioning of buildings for human occupancy. It considers the mechanical performance of an air handling unit as a whole and will be supported by a standard for sections and components. The position of this standard in the whole field of standards for mechanical building services is illustrated in figure 1. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EN 1886:2007 (E) 5
Figure 1 — Position of this standard in the field of mechanical building services
EN 1886:2007 (E) 6 Introduction This standard specifies the mechanical performance of an air handling unit as a whole to be utilised by all involved in ventilation and air conditioning manufacturing, design, installation and maintenance. The functions and characteristics of the individual sections of the unit will be considered in another series of standards covering air handling units. Because of different requirements due to climatic conditions and building traditions in different parts of Europe, and to the specific features of individual applications, most of the requirements are given in the form of classes, which may be specified to be used in certain regions, or separately for individual applications.
EN 1886:2007 (E) 7 1 Scope This standard specifies test methods, test requirements and classifications for air handling units, which are supplying and/or extracting air via a ductwork ventilating/conditioning a part or the whole of the building. This standard is not applicable to the following: a) air conditioning units serving a limited area in a building, such as fan coil units; b) units for residential buildings; c) units producing ventilation air mainly for a manufacturing process. Except for the thermal and acoustic performance of the casing, the test methods and requirements are applicable to both complete units and any separate sections. The filter bypass test is not applicable to the testing of high efficiency particulate air filters (HEPA). NOTE HEPA filters are recommended to be installed downstream of the air handling unit. Such installations should be leak tested in accordance with the appropriate filter standards. The test method for the thermal performance of the casing is applicable to the comparison of different constructions, but not to the calculation of thermal losses through casing or the risk of condensation. Similarly, the test method for the acoustic performance of the casing is applicable to the comparison of different constructions, but not to the provision of accurate acoustic data for specific units. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 779, Particulate air filters for general ventilation — Determination of the filtration performance EN 1507, Ventilation for buildings — Sheet metal air ducts with rectangular section — Requirements for strength and leakage EN 12237, Ventilation for buildings — Ductwork — Strength and leakage of circular sheet metal ducts EN 12792:2003, Ventilation for buildings — Symbols, terminology and graphical symbols EN 13053:2001, Ventilation for buildings —- Air handling units — Ratings and performance for units, components and sections EN 13501-1, Fire classification of construction products and building elements — Part 1: Classification using test data from reaction to fire tests
EN 61310-1, Safety of machinery — Indication, marking and actuation — Part 1: Requirements for visual, auditory and tactile signals (IEC 61310-1:1995) EN ISO 3743 (all parts), Acoustics — Determination of sound power levels of noise sources — Engineering methods for small, movable sources in reverberant fields EN ISO 3744, Acoustics — Determination of sound power levels of noise sources using sound pressure
— Engineering method in an essentially free field over a reflecting plane (ISO 3744:1994)
EN 1886:2007 (E) 8 EN ISO 11546-2, Acoustics — Determination of sound insulation performances of enclosures —
Part 2: Measurements in situ (for acceptance and verification purposes) (ISO 11546-2:1995) EN ISO 12100-2, Safety of machinery — Basic concepts, general principles for design — Part 2: Technical principles (ISO 12100-2:2003) 3 Terms and definitions For the purposes of this European Standard, the terms and definitions given in EN 12792:2003 and EN 13053:2001 and the following apply. 3.1 air handling unit
real unit factory made encased unit serving as a prime mover of a ventilation or air conditioning installation where outdoor air, recirculated air or extract air is treated, consisting of a fan section where a filter section and heat exchanger may be connected. In addition the unit may consist of an inlet section with one or more louvres and dampers, a mixing section, heat recovery section, one or more heating and cooling coils, humidifiers, sound attenuators and additional equipment such as controls, measuring sections etc. 3.2 air handling unit
model box special test unit (defined in 8.3.2) used to execute measurements for general classification, comparison or categorisation of series or individual casings 4 Usage of real units and/or model boxes for the verification of mechanical performances For clear and non-ambiguous differentiation, it shall always be indicated whether the measurement has been made on the real unit or on the model box by using the letter "M" for the model box and "R" for the real unit in documentation. Test criteria of model boxes and real units are presented in Table 1.
EN 1886:2007 (E) 9
Table 1 — Test criteria of model box and real unit Kind of casing Test criteria Model box (M) Real unit (R) Mechanical strength General classification of casing construction Particular classification of casing construction and individual evaluationAir leakage General classification of casing construction Particular classification of casing construction and individual evaluationFilter bypass leakage General classification of casing construction Particular classification of casing construction and individual evaluationThermal transmittance General classification of casing construction --- Thermal bridging General classification of casing construction --- Acoustic insulation General classification of casing construction ---
5 Mechanical strength of casing 5.1 Requirements and classification Air handling unit casings shall be categorised into classes in accordance to Table 2. Table 2 — Casing strength classification of air handling units Casing class Maximum relative deflection mm × m-1 D1 D2 D3 4 10 exceeding 10 NOTE The leakage test shall be done after the strength test.
For clear and non-ambiguous differentiation it shall always be indicated whether the measurement was made on the real unit or on the model box by using letter "M" for the model box and "R" for the real unit in documentation. EXAMPLE D1 (M) Class D1 and Class D2 casings shall be designed and selected so that the maximum deflection of any span of the panels and/or frames does not exceed the limits in Table 2 (see Figure 2).
EN 1886:2007 (E) 10 The casings of class D1, D2 and D3 have to withstand the maximum fan pressure (not shock pressure) at the selected design fan speed. No permanent deformation (hysteresis maximum
± 2,0 mm per m frame/panel span) of the structural parts (structures and supports) or damage of the casing may occur. Table 3 — Test pressures Kind of casing Test criteria Model box (M) Real unit (R) Deflection ± 1 000 Pa Normal operating conditions at selected design fan speed Withstand maximum fan pressure ± 2 500 Pa Maximum fan pressure at selected design fan speed
Parts of the real unit, which are running under positive pressure, shall be tested under positive pressure. Parts of the real unit, which are running under negative pressure, shall be tested under negative pressure. Deviating test pressures shall be specified between the manufacturer and purchaser.
EN 1886:2007 (E) 11
Key A
Panel deflection B
Frame deflection Figure 2 — Illustration of panel and frame spans of air handling units
The ability of the real unit to withstand the maximum designed fan pressure may be demonstrated by prior agreement between the manufacturer and purchaser, by blanking off the inlets to the unit and running the fan up to its design operating speed. Downstream sections of blow-through units shall be proved by blanking off the air handling unit's outlets. Any special requirements, for example the ability to survive shock loading caused by sudden closure of fire dampers, should be clearly specified.
EN 1886:2007 (E) 12
Figure 3 — Deflection of panels and frames of air handling units 5.2 Testing Deflection shall be measured within an accuracy of ± 0,5 mm whilst the air handling unit is operating under test conditions. For example, referring to Figure 3, deflection X'X" is measured for span R'S', deflection XX" is measured for span PQ. Deflection X'X" is a function of panel stiffness. Deflection XX" is a function of both frame and panel stiffness. Frame deflection is RR' and SS'. EXAMPLE PQ = 2m R'S' = RS = 1 m Measured deflection XX" = 8 mm Measured deflection X'X" = 5 mm
EN 1886:2007 (E) 13 Hence, the deflection of span R'S' is 5 mm × m-1 and that of span PQ is 4 mm × m-1. The class is determined by the highest value of the measured relative deflections. In this example the deflection of R'S' (the shortest span) determines that class D2 is met. 6 Casing air leakage 6.1 Requirements and classification The leakage test shall be done after the strength test. 6.1.1 Units operating under negative pressure only The air leakage of the assembled air handling unit shall be tested at 400 Pa negative pressure and it shall not exceed the applicable rate given in Table 4. Table 4 — Casing air leakage classes of air handling units, 400 Pa negative test pressure Leakage class of casing Maximum leakage rate (f400)
l × s-1 × m-2 Filter class (EN 779) L1
L2
L3 0,15
0,44
1,32 superior to F9 F8 to F9
G1 to F7 NOTE
The maximal leakage rates given in Table 4 are according to the ductwork leakage classes specified in EN 1507 and EN 12237, (e.g. L2 = B), but the test pressures are different.
NOTE Class L1
for units for special application e.g cleanrooms. In the case of units tested at a pressure deviating from 400 Pa the measured leakage rate shall be converted into a value at reference pressure, using the following formula: 0,65m 400pressure test400
=ff
(1) where:
fm is the measured leakage rate at the actual test pressure;
f400 is the converted leakage rate at 400 Pa , see Table 4. Unless otherwise specified, the applicable rate shall be a function of the efficiency of the air filters within the air handling unit. Where there is more than one stage of air filtration, the classification shall be based on the efficiency of the highest grade of filter. NOTE For special applications by agreement, leakage class may be chosen independent from the filter class. Even if the unit is not equipped with filters, class L3 is still recommended.
EN 1886:2007 (E) 14 6.1.2 Units operating under both negative and positive pressure Air handling units with sections operating under positive pressure shall, in all cases, have the positive pressure sections tested separately from the rest of the unit where the operating pressure immediately downstream of the fan exceeds 250 Pa positive pressure. If the positive pressure does not exceed 250 Pa, a negative pressure test shall be sufficient. The test pressure applied to the positive pressure sections shall be 700 Pa positive pressure or the air handling unit's maximum positive operating pressure, whichever is the greater. The remainder of the unit shall be tested in accordance with 6.1.1, with the applicable leakage rate being governed by the efficiency of the filter immediately upstream of the fan. It is also allowed to test the entire unit under positive and negative pressure. The air leakage from the sections subjected to 700 Pa positive pressure shall be in accordance with Table 5. Table 5 — Casing air leakage classes of air handling units, 700 Pa positive test pressure Leakage class of casing
Maximum leakage rate (f700) l × s-1 × m-2 L1
L2
L3 0,22
0,63
1,90 NOTE Class L1 for units for special application e.g cleanrooms.
In the case of units tested at a pressure deviating from 700 Pa the measured leakage rate shall be converted into a value at reference pressure, using the following formula: 0,65m 700pressure test700
=ff (2) where
fm is the measured leakage rate at the actual test pressure;
f700 is the converted leakage rate at 700 Pa , see Table 5. Air leakage tests on model boxes shall be performed at both 400 Pa negative pressure and 700 Pa positive pressure. 6.2 Testing 6.2.1 Test apparatus The test apparatus shall be as shown in Figure 4, using a fan with a duty at least capable of meeting the anticipated leakage rate at the respective test pressure(s). If the air handling unit is too large for the capacity of the leakage test apparatus (accuracy ± 3,0 %), or a restriction of access for delivery requires that the unit should be tested in sections or sub-assemblies, the breakdown should be agreed by the manufacturer and purchaser prior to the test date.
EN 1886:2007 (E) 15 Where heat recovery devices are installed, the supply and extract sections shall be tested together as a single unit.
Key 1 AHU under test 5 Flow measurement device 2 AHU test pressure gauge 6 Inlet plate 3 Bleed valve as alternative to variable speed fan 7 Outlet plate 4 Variable speed fan
Figure 4 — Apparatus for testing the casing air leakage (negative pressure test). Typical example 6.2.2 Preparation for test The unit to be tested shall be put up in the plane in which it is intended to operate with its sections connected or joined by the method given in the installation instructions.
EN 1886:2007 (E) 16 Where it is necessary to fit blanking plates, the plates shall be fitted by a similar method to that of the intended installed joint. Openings for electrical, air or water services shall be closed prior to testing. Dampers shall be dismounted before testing or fitted with blanking plates if the damper is inside. The air handling unit shall not incorporate any additional sealing over that of the standard product or, where applicable, of the agreed specification. 6.3 Test procedure Turn on the test apparatus fan unit and adjust until the static test pressure inside the test unit is within 5 % of the specified figure. Keep this pressure constant for 5 minutes, and do not record any readings until the pressure has stabilised. Record the leakage flow rate and the test pressure. 6.4 Determination of allowable leakage rates Calculate the casing surface area from the nominal external dimensions, including the area of the blanked inlet and outlet airflow aperture. The area of components which does not form part of the airtight casing shall be excluded, as well as the area of blanking plates on openings of separately tested unit sections. Leakage results obtained from test pressures deviating from the specified standard test pressure (maximum deviation ± 5 %), shall be converted into leakage rates in accordance with the test pressure classifying the leakage class in Table 4 and/or 5. Determine the maximum allowable leakage from Tables 4 and 5, as appropriate, and relate it to the casing area of the unit under test. The unit shall be deemed passable if the recorded leakage rate is not greater than the allowable leakage rate. If the unit has to be tested in sections, the total sum of the recorded leakage rates for all sections shall be the basis for pass or fail. 7 Filter bypass leakage 7.1 Requirements 7.1.1 General Air bypass around filter cells will decrease the effective efficiency of the filter, especially a high efficiency one, because the bypass air is not filtered. In addition, any inward leakage through the casing downstream of the filter has the same effect. Therefore for filters located upstream of the fan, the air tightness and area of the casing between the filter and the fan are factors that can affect the filter bypass leakage rate. 7.1.2 Acceptable filter bypass leakage rates Table 7 gives the acceptable filter bypass leakage rate, related to different filter classes, as percentages of the specified or nominal air flow rate of the air handling unit to be tested. If the filter is upstream of the fan, leakages of the sections between the filter and fan are deemed to be included in the specified values. In the case of downstream filters the specified values are for the bypass around the filter only.
EN 1886:2007 (E) 17 The acceptable filter bypass leakage rate qva is specified by the formula: vavnom/100qkq=× (3) where
qvnom is the air flow rate of the filter section, see Table 6;
k is the filter bypass leakage rate, in percent of specified or nominal volume flow rate, see Table 7.
Table 6 — Air flow rate of the filter section (qvnom) subject to the kind of unit Kind of unit Test criteria Model box (M) Real unit (R) Volume flow rate Corresponds to a filter face velocity of 2,5 m/s (e.g. 0,93 m³/s at 610 × 610 mm) Normal operating conditions at selected design fan speed
Table 7 — Acceptable filter bypass leakage, 400 Pa test pressure Filter class G1 to F 5 F 6 F 7 F 8 F 9 Maximum filter bypass leakage rate k in % of the volume flow rate 6 4 2 1 0,5 Tabulated percentages represent the leakage of unfiltered air. Unfiltered air for filters located upstream the fan is considered to be the bypass leakage around the filter cells plus the casing air leakage of the sections between the filter and the fan. Unfiltered air for filters located downstream the fan is considered to be the bypass leakage around the filter cells only. The unit shall be deemed to pass if the specified value for the filter bypass leakage rate, determined in 7.2, is no greater than the acceptable filter bypass leakage rate qva. 7.1.3 Two or more filter sections in the same unit If two or more filter sections are provided within the air handling unit, the filter bypass leakage shall be tested separately for each filter. 7.2 Testing 7.2.1 General The specified test requirements refer to the complete air handling unit.
EN 1886:2007 (E) 18 The filter cells shall be removed and replaced with blanking plates, e.g. as shown in Figure 5. These plates shall have exactly the same shape, dimensions and surface quality as the filter cell in the area relevant to air tightness. Alternativel
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.