EN ISO 29462:2013

SLOVENSKI STANDARD
01-september-2013
7HUHQVNRSUHVNXãDQMHVSORãQLKSUH]UDþHYDOQLKILOWULUQLKQDSUDYLQVLVWHPRYQD
NUDMXVDPHPNUDMXYJUDGQMHJOHGHXþLQNRYLWRVWLRGVWUDQMHYDQMDGHOFHYSRQMLKRYL
YHOLNRVWLLQJOHGHXSRUQRVWLSURWL]UDþQHPXWRNX,62
Field testing of general ventilation filtration devices and systems for in situ removal
efficiency by particle size and resistance to airflow (ISO 29462:2013)
Betriebserprobung von Filtereinrichtungen und -systemen für die allgemeine Lüftung
hinsichtlich ihrer Abscheideeffizienz im eingebautem Zustand bezogen auf die
Partikelgröße und den Druckverlust (ISO 29462:2013)
Essais in-situ de filtres et systèmes de ventilation générale pour la mesure de l'efficacité
en fonction de la taille des particules et de la perte de charge (ISO 29462:2013)
Ta slovenski standard je istoveten z: EN ISO 29462:2013
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
23.120 =UDþQLNL9HWUQLNL.OLPDWVNH Ventilators. Fans. Air-
QDSUDYH conditioners
91.140.30 3UH]UDþHYDOQLLQNOLPDWVNL Ventilation and air-
VLVWHPL conditioning
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 29462
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2013
ICS 91.140.30
English Version
Field testing of general ventilation filtration devices and systems
for in situ removal efficiency by particle size and resistance to
airflow (ISO 29462:2013)
Essais in situ de filtres et systèmes de ventilation générale Betriebserprobung von Filtereinrichtungen und -systemen
pour la mesure de l'efficacité en fonction de la taille des für die allgemeine Lüftung hinsichtlich ihrer
particules et de la perte de charge (ISO 29462:2013) Abscheideeffizienz im eingebautem Zustand bezogen auf
die Partikelgröße und den Druckverlust (ISO 29462:2013)
This European Standard was approved by CEN on 1 March 2013.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC 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 translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2013 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 29462:2013: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
This document (EN ISO 29462:2013) has been prepared by Technical Committee ISO/TC 142 "Cleaning
equipment for air and other gases" in collaboration with Technical Committee CEN/TC 195 “Air filters for
general air cleaning” the secretariat of which is held by UNI.
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 September 2013, and conflicting national standards shall be
withdrawn at the latest by September 2013.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 29462:2013 has been approved by CEN as EN ISO 29462:2013 without any modification.
INTERNATIONAL ISO
STANDARD 29462
First edition
2013-03-15
Field testing of general ventilation
filtration devices and systems for in
situ removal efficiency by particle size
and resistance to airflow
Essais in situ de filtres et systèmes de ventilation générale pour la
mesure de l’efficacité en fonction de la taille des particules et de la
perte de charge
Reference number
ISO 29462:2013(E)
©
ISO 2013
ISO 29462:2013(E)
© ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved

ISO 29462:2013(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, and abbreviations . 1
3.1 Terms and definitions . 1
3.2 Abbreviations . 3
4 Test equipment and setup . 3
4.1 Particle counter . 3
4.2 Diluter . 3
4.3 Pump . 4
4.4 Sampling system . 4
4.5 Air velocity measurement instrument . 6
4.6 Relative humidity measurement instrument . . 6
4.7 Temperature measurement instrument . 6
4.8 Resistance to airflow measurement instrument . 6
4.9 Test equipment maintenance and calibration . 7
5 Site evaluation . 7
5.1 General . 7
5.2 Filter installation pre-testing inspection . 7
5.3 Approval for testing . 7
6 Test procedure . 8
6.1 Air velocity . 8
6.2 Relative humidity . 8
6.3 Temperature . 8
6.4 Resistance to airflow . 9
6.5 Removal efficiency . 9
6.6 Sampling probes .12
7 Expression of results .14
7.1 General information .14
7.2 Data collection .15
8 Errors and data analyses .16
8.1 General .16
8.2 Relative humidity .16
8.3 Air temperature .16
8.4 Aerosol composition .16
8.5 Uniformity of aerosol concentration .17
8.6 Coincidence errors — Particle counter .17
8.7 Particle losses.17
9 Calculation of results .17
9.1 Calculation of removal efficiency .17
9.2 Calculation of uncertainty .20
9.3 Coefficient of variation (CV) .20
10 Optional enhanced test system .21
10.1 Application of enhanced test .21
10.2 Principle of the enhanced test system .22
10.3 Determination of the corrected particle size .23
10.4 Presentation of results .24
Annex A (informative) Filter installation pre-testing inspection form .25
ISO 29462:2013(E)
Annex B (informative) Approval for testing form .28
Annex C (informative) Example of how to complete testing .30
Bibliography .46
iv © ISO 2013 – All rights reserved

ISO 29462:2013(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 29462 was prepared by Technical Committee ISO/TC 142, Cleaning equipment for air and other gases.
ISO 29462:2013(E)
Introduction
The purpose of this International Standard is to provide a test procedure for evaluating the in-situ
performances of general ventilation filtration devices and systems. Although any filter with a filtration
efficiency at or above 99% or at or below 30% when measured at 0,4 μm could theoretically be tested
using this International Standard, it may be difficult to achieve statically acceptable results for these
type of filtration devices.
Supply air to the Heating, Ventilation and Air-Conditioning (HVAC) system contains viable and non-
viable particles of a broad size range. Over time these particles will cause problems for fans, heat
exchangers and other system parts, decreasing their function and increasing energy consumption and
maintenance. For health issues, the fine particles (<2,5 µm) are the most detrimental.
Particles in the 0,3 μm to 5,0 μm size range are typically measured by particle counters that can
determine the concentration of particles in specific size ranges. These instruments are commercially
available and will determine particle size along with the concentration level by several techniques (e.g.,
light scattering, electrical mobility separation, or aerodynamic drag). Devices based on light scattering
are currently the most convenient and commonly used instruments for this type of measurement and
are therefore the type of device used within this International Standard.
Particles in the size range 1,0 μm to 5,0 μm are present in low numbers (less than 1%, by count) in outdoor
and supply air and have higher sampling-system losses. Results in the range >1,0 μm will therefore have
lower accuracy and so the results should be interpreted with respect to this.
During in-situ measurement conditions, the optical properties of the particles may differ from the optical
properties of the particles used for calibrating the particle counter and testing it in the laboratory. Thus
the particle counter could size the particles differently but count the overall number of particles correctly.
By adding an extra reference filter, the effect of varying measuring conditions can be reduced. Additionally,
using this enhanced test method, the results can be used to correct the measured efficiencies in relation
to the efficiency of the reference filter measured in laboratory using a standardized test aerosol.
The results from using the standard method or the enhanced method will give both users and
manufacturers a better knowledge of actual filter and installation properties.
It is important to note that field measurements generally result in larger uncertainties in the results
compared to laboratory measurements. Field measurements may produce uncertainty from temporal
and spatial variability in particle concentrations, from limitations on sampling locations due to air
handling unit configurations, and from the use of field instrumentation. These factors may result in lower
accuracy and precision in the calculated fractional efficiencies compared to laboratory measurements.
This International Standard is intended to provide a practical method in which the accuracy and precision
of the result are maximized (and the precision of the result quantified) by recommending appropriate
sampling locations, sample quantities, and instrumentation. This International Standard is not intended
to serve as a filter performance rating method. The results obtained from the test method described in
this International Standard do not replace those obtained through tests conducted in the laboratory.
vi © ISO 2013 – All rights reserved

INTERNATIONAL STANDARD ISO 29462:2013(E)
Field testing of general ventilation filtration devices and
systems for in situ removal efficiency by particle size and
resistance to airflow
1 Scope
This International Standard describes a procedure for measuring the performance of general ventilation
air cleaning devices in their end use installed configuration. The performance measurements include
removal efficiency by particle size and the resistance to airflow. The procedures for test include the
definition and reporting of the system airflow.
The procedure describes a method of counting ambient air particles of 0,3 μm to 5,0 μm upstream and
downstream of the in-place air cleaner(s) in a functioning air handling system. The procedure describes
the reduction of particle counter data to calculate removal efficiency by particle size.
Since filter installations vary dramatically in design and shape, a protocol for evaluating the suitability
of a site for filter evaluation and for system evaluation is included. When the evaluated site conditions
meet the minimum criteria established for system evaluation, the performance evaluation of the system
can also be performed according to this procedure.
This International Standard also describes performance specifications for the testing equipment and
defines procedures for calculating and reporting the results. This International Standard is not intended
for measuring performance of portable or movable room air cleaners or for evaluation of filter installations
with and expected filtration efficiency at or above 99 % or at or below 30 % when measured at 0,4 μm.
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.
ISO 7726, Ergonomics of the thermal environment — Instruments for measuring physical quantities
ISO 14644-3, Cleanrooms and associated controlled environments — Part 3: Test methods
ISO 21501-4, Determination of particle size distribution — Single particle light interaction methods —
Part 4: Light scattering airborne particle counter for clean spaces
3 Terms, definitions, and abbreviations
3.1 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1.1
air filter bypass
unfiltered air that has passed through the AHU filter installation but remained unfiltered because it
bypassed the installed air filters
ISO 29462:2013(E)
3.1.2
air velocity
rate of air movement at the filter
Note 1 to entry: It is expressed in m/s (fpm) to three significant figures.
3.1.3
allowable measurable concentration of the particle counter
fifty percent of the maximum measurable concentration as stated by the manufacturer of the particle counter
3.1.4
coefficient of variation
CV
standard deviation of a group of measurements divided by the mean
3.1.5
diluter
dilution system
system for reducing the sampled concentration to avoid coincidence error in the particle counter
3.1.6
filter efficiency
removal efficiency of a filter as determined by this International Standard, where upstream and
downstream particle count measurements are taken close to the filter being tested
3.1.7
filter installation
filtration devices and systems such as a single filter or a group of filters mounted together with the same
inlet and outlet of air
3.1.8
general ventilation
process of moving air from outside the space, recirculated air, or a combination of these into or about a
space or removing it from the space
3.1.9
isoaxial sampling
sampling in which the flow in the sampler inlet is moving in the same direction as the flow being sampled
3.1.10
isokinetic sampling
technique for air sampling such that the probe inlet air velocity is the same as the velocity of the air
surrounding the sampling point
[Source: ISO 29464:2011; 3.1.144]
3.1.11
particle counter
device for detecting and counting numbers of discrete airborne particles present in a sample of air
[Source: ISO 29464:2011; 3.1.27]
3.1.12
particle size range
defined particle counter channel
3.1.13
reference filter
small dry media-type filter that has been laboratory tested for removal efficiency by particle size
2 © ISO 2013 – All rights reserved

ISO 29462:2013(E)
3.1.14
removal efficiency by particle size
ratio of the number of particles retained by the filter to the number of particles measured upstream of
the filter for a given particle-size range
3.1.15
resistance to airflow
loss of static pressure caused by the filter and filter loading which is measured with the filter operating
at the measured air velocity
Note 1 to entry: It is expressed in Pa (in WG) to two significant figures.
3.1.16
system efficiency
removal efficiency of a filter system where upstream and downstream particle count measurements
may be across several filter banks or other system components
3.2 Abbreviations
AHU Air Handling Unit
CV Coefficient of Variation
HEPA High Efficiency Particle Air (as per ISO 29463-1)
HVAC Heating, Ventilating and Air-Conditioning
MERV Minimum Efficiency Reporting Value
OPC Optical Particle Counter
RH Relative Humidity
ULPA Ultra Low Penetration Air
VAV Variable Air Volume
VFD Variable Frequency Drive
4 Test equipment and setup
4.1 Particle counter
The particle counter should be capable of measuring particles in the size range 0,3 µm ― 5,0 µm, in a
minimum of four ranges with a minimum of two ranges below 1,0 μm (for example: 0,3 µm ― 0,5 μm,
0,5 µm ― 1,0 μm, 1,0 µm ― 2,0 μm and 2,0 µm ― 5,0 μm). For maintenance and calibration of the particle
counter, see 4.9
4.2 Diluter
A dilution system capable of diluting the aerosol concentration so the particle concentration level is
within the acceptable concentration limit may be used. Choose a suitable dilution ratio so that the
measured concentration of particles is well within the allowable measurable concentration limits of the
particle counter so as to achieve good statistical data (see 9.1.2). If a dilution system is used, it is to be
used for both upstream and downstream sampling. The dilution system shall not change air flow to the
particle counter.
ISO 29462:2013(E)
4.3 Pump
A pump may be used to control the rate of the sample flow (q ) through the sampling probes. A pump is
s
not necessary when the counter flow (q ) to the counter or diluter is sufficient for isokinetic sampling.
pc
In this case the sample flow (q ) and the counter flow (q ) are the same.
s pc
4.4 Sampling system
4.4.1 General
Figure 1 shows the elements of a typical sampling system.
Key
1 sampling downstream 6 diluter
2 manometer 7 particle counter
3 valve 8 q – flow to particle counter
pc
4 Computer 9 pump
5 q – primary flow 10 flow meter
s
Figure 1 — Sampling system
4.4.2 Sampling probes
The sampling probe should consist of a sharp edged nozzle connected to the sample line leading to the
auxiliary pump or particle counter. The diameter of the nozzle is dependent on the sample flow (q ) in
s
order to get isokinetic sampling. The diameter should not be less than 8 mm.
4 © ISO 2013 – All rights reserved

ISO 29462:2013(E)
4.4.3 Sampling lines
Sampling lines upstream and downstream should be of equal length and as short as possible to avoid
losses. Material should preferably be of a type with minimum particle losses for filter installations.
[2]
Software is available to calculate line losses.
4.4.4 Sampling locations
Sampling locations should be placed close to the filter as shown in Figure 2. If the system efficiency is
to be tested, the sampling locations should be further away to achieve good mixing of airflow through
filters, frames, doors, etc. Measurement the system efficiency is more difficult and therefore it is good
practice to plan the measurement carefully and describe in detail how it was made.
Key
A minimum distance between the sampling probe and the filter
B distance between the end of the filter and the sampling probe
C location of sample points in y-z plane for filter efficiency tests
1 downstream sampling probe location for filtration system efficiency test
Figure 2 — Sample locations
4.4.5 Valve (manual or automatic)
A valve may be used to switch between upstream and downstream sample locations. The valve should
be constructed so that particle losses are identical in upstream and downstream measurements. No
influence on efficiency due to the valve construction is permitted (for example, four-point ball valves of
sufficient diameter may be used).
4.4.6 Isoaxial sampling nozzle
If a pump (see 4.3) is used to obtain isokinetic sampling, the sample line should then be fitted with an
isoaxial sampling nozzle directly connected to the particle counter or diluter as shown in Figure 3.
ISO 29462:2013(E)
Key
1 pump flow
2 q – flow to particle counter
pc
3 q – sample flow
s
Figure 3 — Isoaxial sampling line to particle counter
4.4.7 Flow meter
A flow meter is necessary if a pump is part of the sampling system. The flow meter should be located
in-line with the pump inlet or outlet.
4.5 Air velocity measurement instrument
The instrument used to measure the air velocity should have sufficient operational limits such that the
system airflow is within the limits of the instrument. The instrument should be chosen in accordance
with ISO 7726 . An instrument that records data values and will average those values is recommended.
Ideally, the instrument should have the ability to correct measurements to standard sea level conditions.
4.6 Relative humidity measurement instrument
The instrument used to measure the relative humidity of the system airflow should have sufficient
operational limits such that the system relative humidity is within the limits of the instrument and
should be chosen in accordance with ISO 7726. An instrument that records data values and will average
those values over time is recommended.
4.7 Temperature measurement instrument
The instrument used to measure the temperature of the system airflow should have sufficient operational
limits such that the system temperature is within the limits of the instrument and should be chosen in
accordance with ISO 7726. An instrument that records data values and will average those values over
time is recommended.
4.8 Resistance to airflow measurement instrument
The instrument used to measure the resistance of the filter bank should have sufficient operational
limits such that the filter bank resistance is within the limits of the instrument, and should be chosen
6 © ISO 2013 – All rights reserved

ISO 29462:2013(E)
in accordance with ISO 14644-3. An instrument that records data values and will average those values
over time is recommended.
4.9 Test equipment maintenance and calibration
Maintenance items and schedules should conform to Table 1.
Table 1 — Apparatus maintenance schedules
After a change that
Incorporated
Maintenance item Annually may alter Comment
into each test
performance
Particle counter zero check X
Sampling system zero check X
Resistance to airflow X
Air velocity X
Temp, RH in sample air stream
X
and at particle counter
Upstream concentration test X
Reference filter test (field) optional
Reference filter test (lab) X X
Particle counter primary
X X
calibration
Temp, RH, air velocity, resist- * or as required by
ance to airflow equipment X* X equipment
calibration manufacturer
Dilution system ratio check X X
Check sample probes for
X
damage
5 Site evaluation
5.1 General
This section identifies the recommended minimum site requirements for performing a removal
efficiency test.
5.2 Filter installation pre-testing inspection
Pre-inspection of filters and air handling units is necessary to determine whether a filter installation is
suitable for evaluation using this International Standard. It is also used to gauge whether any potentially
hazardous conditions exist that would exclude or restrict access to the air handling unit.
Items to inspect include (but are not limited to) those provided in Annex A.
5.3 Approval for testing
Once the pre-testing inspection has been completed and the filter installation determined to be suitable
for testing, then the “approval for testing form” should be completed and signed by representatives of the
building owner or manager and the company performing the testing. A suitable form is shown in Annex B.
ISO 29462:2013(E)
6 Test procedure
6.1 Air velocity
Air velocity through the filter installation should be maintained constant for the duration of the test.
This is possible if the fan speed is controllable through Variable Frequency Drive (VFD) or Variable Air
Volume (VAV) boxes and other modulating dampers are not allowed to adjust. In addition, the percentage
of outside air in the supply air should also be kept constant to reduce fluctuations in particle count that
would influence the test results.
The air velocity at the face of the filters should be measured using the instrument identified in 4.5. Air
velocity measurements may be taken either upstream or downstream of the filters, but downstream
is recommended. Since air velocity can vary significantly over the area of a filter installation, sampling
points should be chosen such that measurements are taken at a minimum of 25 % of the filters and
are distributed uniformly over the area of the filter installation. The measurement device should be
extended away from turbulence caused by personnel or other obstructions. The velocity coefficient of
variation (CV) (see 9.3) should be less than 25 %.
Air velocity measurements should be conducted as close in time to resistance to airflow and removal
efficiency testing as possible. This is to ensure that the system air velocity does not change significantly
between the time of the velocity measurements and the time of the resistance to airflow and removal
efficiency tests. Preferably, air velocity measurements should be conducted before and after the
resistance to airflow and removal efficiency testing, with the velocity measurements averaged.
EXAMPLE
st
1 test: velocity measurement [average velocity = 2,0 m/sec (394 ft/min)]
nd
2 test: resistance to airflow measurements
rd
3 test: removal efficiency testing
th
4 test: velocity measurements [average velocity = 2,2 m/sec (433 ft/min)]
In this example, the reported average velocity would be 2,1 m/sec (414 ft/min).
More frequent velocity measurements may be taken in systems exhibiting a high degree of variability
in velocity over time.
6.2 Relative humidity
The instrument(s) identified in 4.6 should be used for these measurements. The relative humidity (RH)
of the air passing through the filter installation is recommended to be within the range of the particle
counter and/or the RH measurement device used for the duration of the test. If system efficiency is being
determined, the RH should be measured and recorded at the locations of the upstream and downstream
probes. If measuring filter efficiency, the RH should be measured and recorded at one of the locations
of the upstream or downstream probes. In addition, the RH should be recorded at the particle counter
location. Wet-bulb temperature measurements may be used in lieu of RH measurements.
6.3 Temperature
The instrument(s) identified in 4.7 should be used for this measurement. The temperature of the air
passing through the filter installation should be within the operating range of the particle counting
equipment. If system efficiency is being determined, the temperature (i.e., dry-bulb temperature) should
be measured and recorded at the locations of the upstream and downstream probes. If measuring filter
efficiency, the temperature should be measured and recorded at one of the locations of the upstream or
downstream probes. In addition the temperature should be recorded at the particle counter location.
Care should be exercised if temperatures are extreme and/or outside of a normal equipment operating
range. Particle counts should not be measured if temperatures are below freezing (see Clause 8).
8 © ISO 2013 – All rights reserved

ISO 29462:2013(E)
6.4 Resistance to airflow
Resistance to airflow across the filter installation should be measured using the resistance to airflow
instrument(s) identified in 4.8. If existing pressure reading equipment is installed, the resistance to
airflow equipment may be connected to use the existing installed pressure probes. If existing probes are
to be utilized, care shall be taken to ensure the existing probes are properly installed to read the static
pressure and no component of velocity pressure. To read static pressure, the hole in the probe should
be perpendicular to the flow with no obstructions prior to the probe so as to create a vortex. If air is
being forced into the pressure probe, it will read velocity pressure instead of static pressure. Do not use
existing probes if they appear to be bent, broken, clogged, non-functioning or not installed properly so
they will give an accurate reading of the resistance to airflow from the filters only. If the existing probes
cannot be restored to an acceptable level of functioning prior to the testing, they should not be used.
Ideally, resistance to airflow measurements will be recorded for each filter bank separately. However, in
some cases the resistance value recorded will be a combination of multiple filters in series as it will be
physically impossible to measure separate resistance to airflow values.
It is good practice to measure at least 25 values for resistance to airflow over at least two total minutes
and then average the measured values to determine the resistance to airflow. The CV should be calculated
and recorded for this data.
6.5 Removal efficiency
6.5.1 Removal efficiency tests
There are three types of tests described herein.
Filter efficiency
The purpose of this test is to determine the efficiency of the filter(s) for removing airborne particles.
Downstream sampling locations should be chosen such that representative samples of air passing
through the filters are obtained.
System efficiency
The purpose of this test is to determine the efficiency of the filtration system for removing airborne
particles. The filtration system includes the filters and filter-holding frames. Downstream sampling
locations and/or methods should be chosen such that representative samples of the total airflow passing
through the filtration system are obtained. This includes air passing through the filters and around the
filters (i.e. air filter bypass).
Other “system” tests
In addition to measuring filtration performance at the air filtration installation, this International
Standard may also be used to compare the concentration of airborne particles in different sections of an
air handling unit and therefore test the air handling system as a whole.
NOTE In this International Standard the results of other “system” tests are not referred to as “efficiencies”
since the term “efficiency” implies that only particle-removal processes (and not particle addition) are involved.
As the definition of the “system” gets larger due to the addition of other HVAC system components between the
upstream and downstream locations, significant sources of particles (e.g. from leaks in the air handling unit
housing) may affect the downstream particle concentrations.
For example, consider the following air handling unit:
st
1 component: prefilter installation
nd
2 component: cooling coil
rd
3 component: supply fan
ISO 29462:2013(E)
th
4 component: final filter installation
In this example, samples may be taken upstream of the prefilter installation and downstream of the
final filter installation to determine the difference in airborne particle concentrations across the four air
handling unit components as a group. In this case, the “system” consists of all the components between
the upstream and downstream sampling locations.
6.5.2 Sampling method
6.5.2.1 Particle counter instrument
Particle concentrations should be measured using the particle counter identified in 4.1. The same particle
counter shall be used to measure both the upstream and downstream counts because matching of counters
cannot be guaranteed if field particles are different from the laboratory particles used for calibration.
6.5.2.2 Sample volume
Samples for all tests (including the zero test) shall be drawn for the time required to sample 1,0 l
(0,035 ft ) of air or 20 seconds, whichever time is longer. The recommended sample volume is expected
to provide sufficient particle counts for statistically acceptable results according to Clause 9. For a
removal efficiency value to be calculated, the average upstream concentration for the discrete particle
size should be a minimum of 37 counts/l (1 048 counts/ft ).
In some systems the minimum sample volume required may not yield statistically acceptable counts for
all particle sizes. In this case, a longer sampling time can be used to improve the statistical validity of the
measurement. It may not be possible to achieve statistically acceptable results in all particle size ranges.
The sample volume and sample time shall not be changed at any time once particle counting for efficiency
has been started. If a change to sampling volume or sample time is necessary to improve statistical validity,
the test shall be restarted so that all samples are measured using the same sample volume and sample time.
6.5.2.3 Purge sampling lines
Purging should be carried ou
...