ASTM F1471-93
(Test Method)Standard Test Method for Air Cleaning Performance of a High-Efficiency Particulate Air- Filter System
Standard Test Method for Air Cleaning Performance of a High-Efficiency Particulate Air- Filter System
SCOPE
1.1 This test method covers the procedure and equipment for measuring the penetration of test particles through high-efficiency particulate air (HEPA) filter systems using a laser aerosol spectrometer (LAS). This test method provides the capability of evaluating the overall effectiveness of HEPA filter systems consisting of one or two filter stages.
1.2 The aerosols used for testing have a heterodisperse size distribution in the submicrometer diameter range from 0.1 to 1.0 µm.
1.3 The purpose for conducting in-place filter testing by this test method is in the ability to determine penetration of multi-stage installations, without individual stage tests. Particle penetration as low as 10-8 can be measured by this test method. Also, the LAS provides a measure of penetration for discrete particle sizes.
1.4 Maximum penetration for an installed HEPA filter system is 5 X 10-4 for one filter stage, and 2.5 X 10-7 for two stages in series is recommended.
Note 1--Acceptance penetration criteria must be specified in the program, or owners specifications. The penetration criteria suggested in this test method is referenced in Ref (1).
1.5 The values stated in SI units are to be regarded as the standard.
1.6 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.Specific precautionary statements are given in 9.6.
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Designation: F 1471 – 93
Standard Test Method for
Air Cleaning Performance of a High-Efficiency Particulate
Air Filter System
This standard is issued under the fixed designation F 1471; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 Military Standard:
MIL-STD 282 Military Standard Filter Units, Protective
1.1 This test method covers the procedure and equipment
Clothing, Gas Mask Components, and Related Products:
for measuring the penetration of test particles through high-
Performance Test Method
efficiency particulate air (HEPA) filter systems using a laser
aerosol spectrometer (LAS). This test method provides the
3. Terminology
capability of evaluating the overall effectiveness of HEPA filter
3.1 Definitions of Terms Specific to This Standard:
systems consisting of one or two filter stages.
3.1.1 diluter—a device used to reduce the aerosol particle
1.2 The aerosols used for testing have a heterodisperse size
concentration to eliminate coincidence counting is in the LAS.
distribution in the submicrometer diameter range from 0.1 to
3.1.2 dilution ratio—the ratio of the undiluted aerosol
1.0 μm.
particle concentration entering the diluter to the diluted portion
1.3 The purpose for conducting in-place filter testing by this
of the particle concentration. Because diluters have inherent
test method is in the ability to determine penetration of
particle losses that may vary according to the particle size, the
multi-stage installations, without individual stage tests. Particle
−8 dilution ratio may not be constant with respect to size.
penetration as low as 10 can be measured by this test method.
3.1.3 laser aerosol spectrometer (LAS)—a precision particle
Also, the LAS provides a measure of penetration for discrete
detector that allows single particle counting and sizing by the
particle sizes.
amount of scattered light from individual particles, where the
1.4 Maximum penetration for an installed HEPA filter
−4 −7 signals can be grouped into categories corresponding to par-
system is 5 3 10 for one filter stage, and 2.5 3 10 for two
ticle size.
stages in series is recommended.
3.1.4 penetration—the number of particles passing through
NOTE 1—Acceptance penetration criteria must be specified in the
the filter stage, to the number of particles challenging the
program, or owners specifications. The penetration criteria suggested in
upstream side of the filter stage. The penetration, or the
this test method is referenced in Ref (1).
challenge aerosol, may be associated for each particle size of
1.5 The values stated in SI units are to be regarded as the
interest.
standard.
4. Summary of Test Method
1.6 This standard does not purport to address all of the
safety problems, if any, associated with its use. It is the
4.1 A challenge aerosol produced by Di(2-Ethylhexyl) Se-
responsibility of the user of this standard to establish appro-
bacate (DOS) or Di(2-Ethylhexyl) Phthalate (DOP) is injected
priate safety and health practices and determine the applica-
upstream of the filter system and allowed to mix with the
bility of regulatory limitations prior to use. Specific precau-
airstream. Using a LAS, samples of the aerosol are collected
tionary statements are given in Note 2.
from the airstream through probes, both upstream and down-
stream of the filter system. With this test method, the penetra-
2. Referenced Documents
tion of the filter system can be calculated either as a function
2.1 ASTM Standards:
of particle size, or in a particular size of interest. Due to high
F 328 Practice for Determining Counting and Sizing Accu-
particle concentrations that may be required to evaluate the
racy of an Airborne Particle Counter Using Near-
performance of HEPA filter systems, it may become necessary
Monodisperse Spherical Particulate Materials
to dilute the upstream sample to avoid errors due to coinci-
dence counting by the LAS.
4.2 If a diluter is required, the diluter system is calibrated
This test method is under the jurisdiction of ASTM Committee D22 on using lower particle counts of the same aerosol and using the
Sampling and Analysis of Atmospheresand is the direct responsibility of Subcom-
LAS for the measurements (refer to Annex A1 for calibration).
mittee D22.09on ISO TAG for ISO/TC 146.
Current edition approved Feb. 15, 1993. Published April 1993.
The boldface numbers in parentheses refer to a list of references at the end of
this standard. Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700
Annual Book of ASTM Standards, Vol 10.05. Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
F 1471
4.3 Heterodisperse submicrometer aerosols spanning the dence counting losses in the LAS. The diluter must have
diameter range from 0.1 to 1.0 μm are used in the testing. minimum particle losses over the size range of interest and that
the losses are constant with particle size. Calibration of the
5. Significance and Use
diluter is done with the LAS. The diluter calibration procedure
5.1 This test method describes a procedure for determining
is indicated in Annex A2. A schematic diagram of the diluter in
the penetration of aerosols through a one- or twostage HEPA
calibration mode is shown in Fig. A2.1. The diluter calibration
filter installation. Testing multiple filter stages as a single unit
plot is presented in Fig. A2.2. A typical diluter with dimensions
eliminates the need for: installation of auxiliary aerosol bypass
is illustrated in Fig. A2.3.
ducts, installation of aerosol injection manifolds between filter
6.8 Aerosol Generation —It is required that the generator
stages, and entry of test personnel into contaminated areas. It
produce a particle-size distribution covering the diameter range
provides for filter testing without interruption of plant pro-
from 0.1 to 1.0 μm. It must have the capability of achieving up
cesses and operation of ventilation systems.
to 3000 p/s in gas streams when testing multiple-stage HEPA
5.2 The procedure is applicable for measuring penetrations
filter systems.
requiring sensitivities to 0.1 μm.
6.9 For streams where large volumes of aerosol are not
5 3
5.3 A challenge concentration of 2.5 3 10 particles/cm (p/
required, an air-operated or small gas-thermal generator may
3 6
cm ), is required for evaluation of one-filter stage, and 2 3 10
be used.
p/cm , or about 30 μg/L (assuming unit density), is required to
6.10 Injection ports, or manifolds, must be provided for
properly evaluate a two-stage HEPA filter system as one unit.
distributing the aerosol uniformly with the gas stream. Up-
5.4 This test method can determine the penetration of HEPA
stream and downstream probes are required to extract aerosol
filters in the particle-size range from 0.1 to 0.2 μm where the
samples from inside the filter housing. The location of injection
greatest penetration of particles is likely to occur.
ports and sample collection probes or manifolds must be
located in accordance with the requirements in Annex A3.
6. Apparatus
6.11 It is recommended that sample lines between the LAS,
6.1 LAS —The LAS is a particle detector for the purpose of
diluter, and the upstream and downstream probes be the same
sizing and counting single particles in a gas stream. Up to 3000
size and material, and the same length as practicable.
particles per second (p/s) can be counted with less than 10 %
coincidence, or electronic loss at its maximum flow rate. The 7. Reagent and Materials
quantitative particle size distribution shall be a distribution by 8
7.1 DOP or DOS is used as the liquid material to form test
number, not mass, volume, or surface area.
aerosols.
6.2 The test aerosol should be in the diameter range from 9
7.2 Polystyrene Latex Spheres.
0.1 to 1.0 μm.
8. Calibration and Standardization
6.3 The primary particle-size calibration of the LAS by the
manufacturer shall be based on at least three sizes of mono-
8.1 Perform the primary calibration of the LAS by the
disperse polystyrene latex spheres (PSLs), covering the dy-
instrument manufacturer or by qualified personnel using ac-
namic range of the LAS. Calibration standards must be
ceptable standard methods in accordance with Ref (2). Perform
traceable to the National Institute of Standards and Technology
calibrations at regular twelve-month intervals and following
(NIST).
any repair or modification of the instrument. Place a label
6.4 Sample flow accuracy through the LAS of 65% is
showing the due date of the next calibration on the instrument.
required, based on the manufacturer’s specifications. (Refer to
8.2 A check calibration by the operator is recommended
manufacturer’s guide for altitude adjustments of the sample
periodically if the instrument is used continuously or is moved
volume.)
to a new test location requiring vehicle transportation or rough
6.5 The LAS must have the capability for producing a
handling. The calibration check consists of testing the LAS
listing of the particle size distribution over the LAS range. A
with at least two sizes of PSLs. The LAS must correctly size
standard RS-232C interface signal for line printers, tape
the calibration aerosols and reproduce the spectral peak to
recorders, and computers is usually provided with the instru-
within 0.05 μm. If the instrument cannot be adjusted to within
ment.
those calibration limits, then it must be returned to the
6.6 For calibration aerosol having a median size two times
manufacturer for service and calibration. Annex A1 describes a
the minimum detectable size of the LAS, the relative standard
procedure for calibration of the LAS.
deviation of the particle size distribution indicated by the LAS,
8.3 Aerosol Diluter—It is recommended that the same
shall not be increased more than 10 % over the actual relative
aerosol used in the in-place testing be used for diluter calibra-
standard deviation of the calibration aerosol.
tion. If more than one dilution stage is required, each stage
6.7 An aerosol diluter is required to reduce the number of
particles of the upstream sample to avoid significant coinci-
Aerosol generators are available from the following sources: Air Techniques
Division of Hamilton Associates, Inc., Baltimore, MD 21207, Particle Measure-
Laser aerosol spectrometers are available from the following sources: Particle ments Systems, Inc., 1815 South 57th Court, Boulder, CO 80301 (Calibration), and
Measuring Systems, Inc., 1815 South 57th Court, Boulder, CO 80301, TSI Nuclear Consulting Services, Inc., P.O. Box 29151, Columbus, OH 43229.
Incorporated Particle Instruments Group, P.O. Box 64394, St. Paul, MN 55164, and Di(2-Ethylhexyl) Phthalate (DOP) and Sebacate (DOS) are available from C.P.
Met One, Inc., 481 California Avenue, Grants Pass, OR 97526. Hall Co., Chicago, IL 60635, and Nuclear Consulting Services, Inc., P.O. Box
Available from TSI Incorporated Particle Instrument Group, P.O. Box 64394 St. 29151, Columbus, OH 43229.
Paul, MN 55164. Available from Duke Scientific Corp., Palo Alto, CA 94303.
F 1471
must be calibrated independently. A procedure for calibration the sample line from the LAS to the diluter. Sampling periods
of the diluter using the LAS is outlined in Annex A2. are usually 20 s, refer to Annex A2.
9.8 Purge the sample collection system and zero the LAS
9. Procedure
before proceeding to the next step in the procedure. The
9.1 An example of an in-place filter test system and sam- purging procedure is described in A2.1.2 of Annex A2.
pling arrangement is illustrated in Fig. 1. Components include
9.9 Accumulate two successive samples from the down-
the gas-flow duct, filter housing with filters, the LAS, diluter,
stream location. Sampling time periods should be selected to
and aerosol generator.
yield net particle counts over background of at least 100.
9.2 Aerosol Mixing Uniformity Tests— Conduct these tests
A10-min sampling period is usually sufficient. The difference
upon completion of initial installation and after any modifica-
between each set of samples shall not exceed 5 % of the larger
tions or repair to the filter system. It is not required to conduct
count. If penetration of only one filter stage is being measured,
these tests each time the in-place test is performed. However,
shorter sampling times may be used because of higher particle
if aerosol mixing and sampling parameters are changed, then
counts. If significant penetration is experienced downstream of
new air aerosol mixing uniformity tests are required. Refer to
one-filter stage and coincidence counting is suspected in the
Annex A3 for procedure.
LAS, then the diluter must be used in the sample line. See 6.1
9.3 Measure the airflow of the test gas stream and the
and 6.7.)
resistance across the filter stage following the procedure
outlined in Annex A3. 10. Calculation
9.4 Establish the arrangement of sample lines between the
10.1 Calculate the penetration of the filter system for each
probes, the diluter, and LAS. Make the upstream and down-
discrete particle-size. The equation holds for each specific size
stream sample lines as equal in length as practicable.
particle diameter as:
9.5 Because of expected low particle counts that can pen-
C 2 C
d b
etrate HEPA filter systems, it is necessary to measure the
P 5 (1)
C D
u
non-test particles in the gas stream to serve as background
samples. With no aerosol generation and no sample dilution,
where:
use the LAS to sample the gas stream from the downstream
P = penetration,
sample probe only. Collect samples at this location for the
C = particle counts downstream,
d
same duration as will be required for the test aerosol. The
C = particle counts of background,
b
background particle counts may vary depending on external C = particle counts upstream, and
u
D = dilution ratio.
leaks to the filter housing, but should not exceed 30 % of the
expected test aerosol. If higher background particles are found 10.2 To calculate the uncertainty of the upstream and
than those suggested and if leaks in the filter housing are
downstream penetration measurements, a theoretical value was
suspected, they must be plugged before testing can continue. used in the following equation. The value is based on standard
9.6 Generate the challenge aerosol at the suggested particle
propagation-of-error techniques neglecting covariance terms
concentration, see 5.3. and using Poisson statistics to estimate uncertainties. The
equation is as follows:
NOT
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