EPA/600/A-96/048
95-TA33A.04
Aerosol Filtration Efficiency of
Ventilation Air Cleaners
James T. Hanley and David S. Ensor
Research Triangle Institute
P.O. 12194
Research Triangle Park, NC 27709
Leslie E. Sparks
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711

-------
95-TA33A.04
INTRODUCTION
The use of air cleaners has steadily moved from one of protecting equipment (such as the heat
exchanger in a furnace) to one of protecting people from objectionable indoor aerosol particles (e.g.,
common dust and allergens). This shift has necessitated the development of new test methods for
determining air cleaner filtration efficiency. Under a cooperative agreement with the U.S.
Environmental Protection Agency (EPA)1 and contracts with the American Society of Heating,
Refrigerating and Air-Conditioning Engineers (ASHRAE)2, and the Canadian Electrical Association
(CEA)\ the Research Triangle Institute (RTI) has developed a test method for measuring the
fractional aerosol filtration efficiency of air cleaners. The method provides a reliable and accurate
means of measuring air cleaner fractional efficiencies over the particle diameter size range of 0.01 to
10 H-m.
The need for a fractional efficiency test comes from several sources: (1) the growing concern with
indoor air quality (IAQ); (2) the fact that filtration efficiency is often highly particle-size dependent
for particles <10 |im in diameter; (3) limitations of the current ASHRAE efficiency test (52.1-1992)
which, by design, cannot differentiate between particle sizes4; and (4) that respirable particles are
generally classified as those <10 p.m in diameter.
Implementation of the new method will provide several benefits to the air cleaner community:
•	Fractional efficiency data that will allow architects, building managers, and heating,
ventilating, and air-conditioning (HVAC) supervisors to specify air cleaners to meet their
filtration requirements;
•	Manufacturers with a standardized fractional efficiency test of known data quality to
replace the many nonstandard methods now in use;
•	Architects and IAQ researchers with fractional filtration efficiency data required for use in
air cleaning system designs and IAQ models; and
•	The consumer with a more realistic assessment of air cleaner performance than is currently
given by the single-valued efficiency and arrestance tests.
Furthermore, because the new method provides a more detailed assessment of an air cleaner's
performance than the current efficiency and weight arrestance tests of ASHRAE 52.1-1992, use of
the new method may lead to the development of improved air cleaners.
TEST DUCT
The test duct, aerosol generation, and aerosol sampling systems are illustrated in Figure 1. Like an
ASHRAE duct, the test duct is based on a 24 x 24 in. (610 x 610 mm) duct and accommodates the
fractional efficiency tests as well as the dust loading and arrestance tests. Key features of the duct
include:
•	Positive pressure to minimize room air infiltration;
2

-------
95-TA33A.04
•	Inlet air drawn from indoors to maintain temperature and humidity within the desired
range;
•	HEPA (high efficiency particulate air)-filtered inlet to remove ambient aerosol;
•	HEPA-filtered exhaust to allow indoor discharge;
•	Artificially generated, solid-phase, polydisperse potassium chloride (KC1) salt challenge
aerosol, generated from an aqueous solution using an air-atomizing nozzle;
•	Automated sequential upstream/downstream aerosol sampling;
•	A downstream mixing baffle (in addition to the upstream mixing baffle) to ensure well-
mixed aerosol conditions at downstream sample probes; and
•	180° bend in the downstream duct to bring upstream and downstream sample locations
close to each other, greatly reducing sample line length and facilitating use of a single set
of aerosol measurement instrumentation.
AEROSOL GENERATION, SAMPLING, AND MEASUREMENT
The test aerosol was composed of KC1 generated from aqueous solution. KC1 was selected because
of its relatively high water solubility, high deliquescence humidity, known crystalline structure
(facilitates complete drying), solid phase, and low toxicity. The aqueous solution was prepared by
combining 300 g of KC1 with 1 L of distilled water.
A solid-phase aerosol was desired because, due to particle bounce, solid particles tend to penetrate
air cleaners at a higher rate than do liquid particles. Thus, using solid-phase aerosol particles
provides a more stringent test. At particle sizes above a few micrometers, differences between
aerosol penetration measured using solid- and liquid-phase aerosols can be very large for some air-
cleaning devices, particularly for low efficiency filters.
To span the size range from 0.01 to 10 Jim, three methods of aerosol generation and three methods
of aerosol measurements were used (Table 1). This was necessary to optimize measurement
accuracy over the entire size range.
From 0.01 to 0.07 (im, the up- and downstream aerosol concentrations were measured with a TSI,
Inc., Model 3071 Electrostatic Classifier with a Model 3020 Condensation Nucleus Counter. This
instrument measures particle size based on the electrical mobility of the aerosol particles. A Laskin
Nozzle using a dilute 0.1% by weight KC1 aqueous solution was used to generate the challenge
aerosol.
From 0.09 to 3 pim, the aerosol concentrations were measured with a Particle Measuring Systems,
Inc. (PMS) LAS-X Laser Aerosol Spectrometer. This instrument measures particle size based on
wide-angle light scattering using a laser light source to illuminate the particles. A Collison nebulizer
containing a 20% by weight KC1 solution was used to generate the test aerosol.
3

-------
95-TA33A.04
A Climet Instruments Company Model 226 Optical Particle Counter (OPC) with Model 8040
Multichannel Analyzer was used to measure aerosol concentrations over the range of 0.3 to 10 fim
diameter. This is a wide-angle light scattering instrument that uses a high intensity white-light
illumination source. The aerosol was generated by nebulizing 20% by weight aqueous KC1 solution
with a two-fluid (air and water) air atomizing nozzle as illustrated in Figure 1.
The aerosol output from each generator was injected into a spray tower (as shown in Figure 1). The
tower served two purposes. It allowed the salt droplets to dry by providing an approximate 40
second mean residence time and it allowed larger-sized particles to fall out of the aerosol. After
generation, the aerosol passed through a TSI Model 3054 aerosol neutralizer (Kr85 radioactive
source) to neutralize any electrostatic charge on the aerosol (electrostatic charging is an unavoidable
consequence of most aerosol generation methods). To improve the mixing of the aerosol with the air
stream, the aerosol was injected counter to the airflow as illustrated in Figure 1.
SYSTEM QUALIFICATION TESTS
As part of a program with EPA, the new test duct was put through a series of system qualification
tests to demonstrate its capability to accurately measure fractional efficiency. The purpose of these
tests was to quantify that the test rig and sampling procedures were capable of providing reliable
fractional penetration measurements. It is strongly recommended that such tests be included in the
new test standard. Similar qualification tests are specified in the Institute of Environmental Sciences
Recommended Practice "Testing ULPA Filters"5 and are an important part of any quantitative test
method.
Qualification tests were performed for:
•	Airflow uniformity in the test duct,
•	Aerosol uniformity in the test duct,
•	Downstream detection of aerosol,
•	Overloading tests of the OPC,
•	0% penetration test,
•	100% penetration test,
•	Aerosol generator response time,
•	Duct leak test, and
•	Duct temperature and relative humidity.
Table 2 summarizes the results from the system qualification tests. (In the table, "CV" is the
coefficient of variation which is equal to the standard deviation of a set of measurements divided by
their mean.) Also included are recommended goals for these parameters. In specifying these goals,
the objective was to have tight enough control over the critical test parameters to yield accurate and
reproducible results and yet not be so tight that the test becomes unrealistically difficult or expensive
to perform. The recommended levels are based on a combination of judgment as to what will be
required for dependable results and practical experience in trying to achieve optimum test conditions.
All of the recommended levels were met or exceeded in the test duct. As data from interlaboratory
comparisons become available, these goals may need to be strengthened to improve interlaboratory
comparison or relaxed to increase the utility of the method.
4

-------
95-TA33A.04
Results from the 100% penetration tests are presented in Figure 2. These tests provide a relatively
stringent test of the adequacy of the overall duct, sampling, rfieasurement, and aerosol generation
system. The test is performed as a normal penetration test except that no air cleaner is used. A
perfect system would yield a measured penetration of 1 at all particle sizes. Deviation from 1 can
occur due to particle losses in the duct, differences in the degree of aerosol uniformity (i.e., mixing)
at the upstream and downstream probes, and differences in particle transport efficiency in the
upstream and downstream sample lines. Results show that, at particle sizes below about 2 (im, the
losses were less than 2%. Maximum loss of approximately 10% was observed in the 4 to 10 |im
range.
TEST PROCEDURES
The penetration was calculated from the average of 10 upstream and 10 downstream samples taken
sequentially (i.e., one upstream, one downstream, one upstream, one downstream, . . . until 10 each
were obtained). This sequential sampling scheme minimizes the effect of aerosol generator
variability. Each sample was 2 min in duration. This was based on having the sample duration long
enough to obtain a minimum of 50 particles counted in each sizing channel for each upstream sample
(providing a minimum total of 500 particle counts in each channel for the combined 10 upstream
samples). For each test, measurements were also made with the aerosol generator off to measure the
upstream and downstream background aerosol concentrations.
For each test, we have the following information for each particle size:
•	A series of background upstream and downstream measurements performed with the
aerosol generator off. These are averaged to obtain Ubkg and Dbkg.
•	A series of upstream and downstream particle counts performed with the aerosol
generator on. These are averaged to obtain Uavg and Davg.
•	A series of 0% filtration efficiency correction factors, F0.
From these quantities, the filtration efficiency at each particle size was computed as:
Filtration Efficiency = 1 - ( 1-F0) (Davg - Dbkg) / (Uavg - Ubkg) .
RESULTS
A series of triplicate tests was performed with the test air cleaners (Table 3) to illustrate the
characteristic shape of the fractional efficiency curves for the various air cleaners. Under the
ASHRAE program, the test air cleaners consisted of a furnace filter, a pleated-paper filter, and a
two-stage electrostatic precipitator (ESP). The fractional efficiency measurements were made over
the size range of 0.3-10 (im. Under the CEA program, the air cleaners consisted of a furnace filter, a
single-stage ESP, a charged-media electronic air cleaner (EAC), and a two-stage ESP. The fractional
efficiency measurements on the CEA program covered the size range from approximately 0.01 to
5

-------
95-TA33A.04
10 )im. On each program, the devices were selected to cover a wide range of filtration efficiencies.
Figures 3 and 4 summarize the fractional efficiency results.
Table 4 shows the upstream and downstream particle counts associated with one of the pleated-paper
air cleaner tests covering the 0.3 - 10 (im size range. The upstream counts were similar for the other
tests with the downstream counts dependent upon the degree of particle penetration of the air cleaner.
A misunderstanding often encountered in fibrous filter testing is that an air cleaner's filtration
efficiency will continuously decrease as the particle size decreases. Actually, this statement holds
true only over a certain range of particle sizes and this range is dependent on the filter media. For
example, most media-based air filters are least efficient at particle diameters of about 0.2 to 0.3 |im.
For both larger and smaller particles, efficiency increases. The increase in efficiency for larger
particles results from increased effectiveness of the filtration processes to collect particles due to the
physical mechanisms of inertial impaction and interception, as well as straightforward sieving of
particles when the particle diameter is greater than the "pore size" of the filter. The increase in
efficiency for smaller particles is caused by diffusion. Particle diffusion is the consequence of the
Brownian motion that small particles undergo due to bombardment by air molecules. Particle
diffusion increases rapidly with decreasing particle size. Thus, smaller particles diffuse to the filter
fibers and are collected more rapidly than larger ones, resulting in increasing filtration efficiency as
particle diameter decreases below 0.1 Jim. Additionally, particle bounce and reentrainment can
reduce an air cleaner's efficiency for the larger particles (i.e., >3 jim diameter). These particles have
sufficient kinetic energy to rebound off the air cleaner's collection surface (e.g., a fiber) and bounce
their way through the air cleaner.
For ESPs, particles are collected by different mechanisms than for filters. Field charging is
responsible for the charging of large particles, and diffusion charging is responsible for the charging
of small particles. Both processes are relatively weak in the 0.1-|im size range, resulting in a relative
minimum in that range. The falloff in efficiency in the 0.01 to 0.03-|im diameter range is attributed
to incomplete charging of these small-diameter particles.
CONCLUSIONS AND RECOMMENDATIONS
Based on the test results, the following principal conclusions are presented:
•	The test system provides a reliable means of evaluating the fractional aerosol efficiency
of air cleaners over the 0.01-10 |im diameter size range. Specification of appropriate
quality control criteria, such as those presented in Table 2 (system qualification tests), are
needed to ensure reliable measurements.
•	Particle loss in the test duct appears to be <10% in the 2 to 10 (im range and <1% at
smaller sizes. These losses were repeatable and relatively low in comparison to the
particle removal efficiency of most air cleaners that will be tested with this method.
Thus, air cleaner penetration data can be confidently corrected for these losses using the
100% penetration data.
•	The fractional efficiency of air cleaners is highly particle-size dependent.
6

-------
95-TA33A.04
• The common furnace filter had fractional efficiencies of <20% over the 0.01 to 10
size range. The highest efficiency was seen for the 2-stage ESP which had a minimum
efficiency of 62% over the entire 0.01 - 10 Jim size range.
ACKNOWLEDGEMENTS
The authors gratefully acknowledge the significant contributions of ASHRAE, CEA, and EPA to this
effort to develop fundamental information on the fractional aerosol efficiency of air cleaners.
REFERENCES
1.	J.T. Hanley, "Fractional Aerosol Filtration Efficiency of In-Duct Ventilation Air
Cleaners," Indoor Air, 4:169-178 (1994).
2.	J.T. Hanley, D.D. Smith, D.S, Ensor, "Define a Fractional Efficiency Test Method That Is
Compatible with Particulate Removal Air Cleaners Used in General Ventilation," Final
Report on ASHRAE Research Project 671-RP, (1992).
3.	Canadian Electrical Association, "Testing Criteria for Electronic Air Cleaners: Phase II,"
(1993).
4.	American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc.
Standard 52.1-1992 "Gravimetric and Dust-Spot Procedures for Testing Air-Cleaning
Devices Used in General Ventilation for Removing Particulate Matter." (1992).
5.	Institute of Environmental Sciences Recommended Practice IES-RP-CC007.1 "Testing
ULPA Filters," Mount Prospect, IL. 1992.
7

-------
95-TA33A.04
Table 1
Aerosol Generators and Measurement Instrumentation
Diameter Size
Range, |im
Aerosol Analyzer
Aerosol Generator
0.01 - 0.07
TSI Model 3071
Electrical Mobility Particle Sizer
with Condensation Nucleus
Counter
Laskin Nozzle with
0.1% by weight KC1
in distilled water.
0.09 - 3
Particle Measurement Systems
Model LAS-X Laser Aerosol
Spectrometer
Collison nebulizer
with 20% by weight
KC1 in distilled
water
0.3 - 10
Climet Model 226 Optical Particle
Counter with Model 8040
Multichannel Analyzer
Two-fluid spray
nozzle
8

-------
95-TA33A.04
/
Table 2. System Qualification Measurements and Goals
Parameter
Level Achieved
Recommended
Goal
Airflow Uniformity:
Based on traverse measurements
made over a 9-pt equal-area grid at
each test flow rate.
CV* = 4.1% @ 1,000 cfm**
CV = 2.7% @ 2,000 cfm
CV = 4.1% @ 3,000 cfm
CV <5%
Aerosol Uniformity:
Based on traverse measurements
made over a 9-pt equal-area grid at
each test flow rate.
CV <7% @ 1,000 cfm
CV <10% @ 2,000 cfm
CV <10% @ 3,000 cfm
CV<10%
Downstream Mixing:
Based on a 9-pt perimeter
injection grid and center-of-duct
downstream sampling.
CV = 4.6% «
CV = 1.0% «
CV= 1.7% «
§ 1,000 cfm
1 2,000 cfm
1 3,000 cfm
CV <5%
0% Penetration Test:
Based on HEPA filter test.
<1%

<1%
100% Penetration Test:
Based on five replicate tests at each
test flow rate.
90 to 100%
for all sizing
channels

90 to 110%
for all sizing
channels
Upper Concentration Limit:
Based on limiting the concentration
to below the level corresponding to the
onset of coincidence error.
10/cm3
(>0.3 n.m)

No pre-
determined level.
Aerosol Generator Response Time
10 minutes

No pre-
determined level.
Duct Leakage:
Ratio of leak rate to test airflow rate.
0.12%

<0.5%
Duct Air Temperature
75 to 85 °F***
50 to 100 °F
Duct Relative Humidity
35 to 55%

<65%
Compressed Air Relative Humidity
<30%

<30%
{*) Coefficient of variation.
(**) 1,000 cfm = 0.47 m3/s.
{***) °C = (°F - 32J/1.8
9

-------
95-TA33A.04
Table 3. Description of the Test Air Cleaners
Air Cleaner	Flow Rate, Size Range,
cfm (L/s)	|j.m
Pleated paper
65% dust-spot efficiency
24 x 24 x 6 in,
(610 x 610 x 150 mm)
2,000
(940)
o
¦
CO
o
Two-Stage ESP
16 x 25 x 6 in.
(406 x 635 x 150 mm)
1,200
(560)
0.3- 10
Furnace Filter
Spun fiberglass
24 x 24 x 1 in.
(610x610x25 mm)
2,000
(940)
0.3 - 10
Two-Stage ESP
16 x 25 x 6 in.
(406 x 635 x 150 mm)
1,000
(470)
0.01 - 10
Single Stage ESP
16 x 25 x 1 in.
(406 x 635 x 25 mm)
1,000
(470)
0.01 - 10
Charged-Media Panel
Electronic Air Cleaner
16 x 25 x 1 in.
(406 x 635 x 25 mm)
1,000
(470)
0.01 - 10
Furnace Filter
Spun fiberglass
16 x 25 x 1 in.
(406 x 635 x 25 mm)
1,000
(470)
0.01 - 10
10

-------
95-TA33A.04
Table 4. Upstream and Downstream Particle Counts from One Test
of the Pleated-Paper Filter
Particle Counts per Indicated OPC Channel (2-Minute Samples @ 0.25 cfm*)
OPC Channel Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Min. Diam. (um)
0.3
0.4
0.5
0.6
0.8
1
1.5
2
3
4
5.5
6
7
8
9
Max. Diam. (um)
0.4
0.5
0.6
0.8
1
1.5
2
3
4
5.5
6
7
8
9
10
Geo. Mean Diam (um)
0.35
0.45
0.55
0.69
0.89
1.2
1.7
24
3.5
4.5
5.7
6.5
7.5
8.5
9.5
Upstream-Bkg
5
0
0
1
0
1
0
1
0
0
0
0
0
0
0
Upstream-Bkg
37
1
0
0
0
0
0
0
0
0
0
0
0
0
0
Upstream-Bkg
6
3
1
0
2
2
4
5
3
7
3
2
1
1
0
Upstream-Bkg
21
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Upstream-Bkg
8
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Upstream
20860
20630
15350
18990
9893
16490
20470
7695
2757
1507
249
339
197
91
39
Upstream
21530
21300
15770
19620
10070
16860
21070
8050
2791
1602
244
361
192
108
58
Upstream
20340
20350
15060
18660
9839
15980
19970
7718
2695
1380
225
281
171
106
58
Upstream
20640
20410
14980
18710
9976
16020
20250
7794
2635
1511
220
360
188
122
65
Upstream
21100
20780
15580
19490
9972
16280
20930
7903
2761
1541
247
315
179
99
59
Upstream
21220
20850
15570
19280
10090
16550
20870
8124
2701
1488
240
342
189
93
62
Upstream
20690
20660
15360
18790
9846
16330
20370
7608
2739
1459
193
342
170
129
51
Upstream
20520
20310
14970
18680
9643
15920
20390
7683
2626
1504
249
327
167
100
52
Upstream
20990
20660
15530
19070
10060
16530
20580
7953
2803
1569
230
327
172
138
69
Upstream
20260
20320
14910
18690
9725
16000
20180
7632
2691
1487
240
340
157
104
50
Upstream-Bkg
142
2
0
0
0
1
0
0
0
0
0
0
0
0
0
Upstream-Bkg
168
0
0
0
0
0
2
1
0
0
0
1
1
1
0
Upstream-Bkg
157
4
1
0
1
0
2
1
0
0
0
0
0
0
0
Upstream-Bkg
142
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Upstream-Bkg
142
0
0
1
0
0
0
0
0
0
0
0
0
0
0
Downstream-Bkg
12
1
1
0
0
0
0
0
0
0
0
0
0
0
0
Downstream-Bkg
37
0
0
0
0
0
1
0
0
0
0
0
0
0
0
Downstream-Bkg
35
13
20
13
4
2
14
7
4
7
2
0
0
0
0
Downstream-Bkg
23
0
0
0
0
0
1
1
1
1
0
0
0
0
0
Downstream-Bkg
16
1
3
6
6
8
15
1
2
0
0
0
1
0
0
Downstream
17060
15830
10940
11670
4938
6056
3353
259
32
22
3
2
1
0
0
Downstream
17030
16010
10920
11640
5027
6036
3424
257
23
12
5
3
2
0
0
Downstream
17280
15840
10920
11990
5004
6021
3363
262
27
14
4
3
1
0
0
Downstream
17180
16120
10930
11580
4952
6047
3370
235
25
3
1
1
1
0
0
Downstream
17400
15980
10890
11640
5028
6124
3464
271
27
18
6
1
2
0
0
Downstream
17280
15800
10860
11590
4881
6004
3342
249
19
14
3
1
0
0
0
Downstream
16530
15270
10540
11280
4960
5851
3168
237
26
6
1
2
1
0
2
Downstream
16950
15500
10680
11330
4866
6024
3358
247
24
1
0
0
1
1
0
Downstream
17370
15790
10970
11700
5033
6007
3347
270
29
13
5
1
1
1
0
Downstream
17680
16370
11170
11930
5154
6239
3529
253
26
8
0
1
3
1
0
Downstream-Bkg
142
0
0
1
1
0
0
0
0
0
0
0
0
0
0
Downstream-Bkg
182
23
18
10
6
2
5
5
1
1
0
1
0
0
0
Downstream-Bkg
148
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Downstream-Bkg
133
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Downstream-Bkg
158
1
0
0
1
0
1
0
0
0
0
0
0
0
0
Meas. Penetration
0.82
0.77
0.71
0.61
0.50
0.37
0.16
0.03
0.01
0.01
0.01
0.00
0.01
0.00
0.00
P100 Correction Value
0.99
0.98
0.99
0.99
0.99
0.99
1.00
0.99
0.98
0.96
0.94
0.96
1.02
1.08
1.14
Corrected Penetration
0.84
0.78
0.72
0.62
0.51
0.37
0.16
0.03
0.01
0.01
0.01
0.00
0.01
0.00
0.00
(*) 0.25 cfm = 0.00012 m3/s.
11

-------
95-TA33A.04
Exhaust
ASME Nozzle
Outlet Filter Bank
Room
Downstream Mixer
Room
Air
OPC
Device
Section
Backup
Filter
Holder
'Used When
)ust-loading)
Inlet Filter
Bank
Upstream Mixer
Blower
Aerosol
Generator
Flow Control
Valve
(*) Optica] Particle Counter
Overview of Test Duct Configuration (Top View)
Spray Nozzle
Spray Tower	j
mF—
Syringe Purrp
Aerosol Charge
Neutnalizer
Dtyii
• Aiomizing Air
/yr" j H£PAF8ter
—£ br Capsules
Air Control Panel
		 Air Source
I ¦*
Test Dud
HEPA
Fiter Bank
Aerosol Generation System
(Side View)
90" Bend to
Point Inlet Upstream
Sample Lines
Vafve
Actuator
Bail Valve
interchangeable
Isokinetic
Sampling Tip
90* Bend to
Point Inlet Upstream
tectricaf
Cable
Downstream Pud
Upstream Duct
Machined 'Y*
Mulichann«
Analyser
Data AcquMlon
Computer
Aerosol Sampling System
(Side View)
Figure 1. Schematic diagram of air cleaner test duct,
aerosol generator, and sampling system.
12

-------
95-TA33A.04
0.9-
0.8-
c 0.7-
0
*| 0.6-
1	0.5-
0.4-
0.3-
0.2- -
0.1-
0.1
Particle Diameter (micrometers)
1,000cfm*--«— 2,000 cfm 3,000 cfm
(*) 1,000 cfm = 0.47 m3/s.
Figure 2. Average results for the 100% penetration tests.
13

-------
95-TA33A.04
100
90
80
^ 70
>
C 60
"o
3= 50
LU
.2 40
15
Ll 30
20
10
0
0.01
Two-Stage ESP
BDOUSSOnBl

Charged-Media EAC Q.
Single-Stage ESP
fa*	1 a
Furnace Filter
i i it i
0.1	1
Particle Diameter (micrometers)
10
Figure 3. Fractional efficiency of several air cleaners
over the 0.01 -10 nm diameter size range.
14

-------
95-TA33A.04
>*
O
c
0)
*¦¦¦
o
it=
LLI
100
90
80
70
60
50
| 40
co
v_
ir 30
20
10
0
0.1
Two-Stage ESP
a^ii
Pieated-Paper
Furnace Filter


10
Particle Diameter (micrometers)
Figure 4. Fractional efficiency of several air cleaners over
the 0.3 -10 nm diameter size range.
15

-------
07„ TECHNICAL REPORT DATA
Jiiixxi-i r LA i 0 (Please read Instructions on the reverse before completir
1, REPORT NO, 2.
EPA/600/A-96/048
3. 1
4, TITLE AND SUBTITLE
Aerosol Filtration Efficiency of Ventilation Air
Cleaners
S. Rt. uni DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
J. T. Hanley and D. S. Ensor (RTI), and L. E. Sparks
(EPA)
8. PERFORMING ORGANIZATION REPORT NO.
95-TA33A.04
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, North Carolina 27709
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
CR817083
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper; 1/92-12/94
14. SPONSORING AGENCY CODE
EPA/600/13
15. supplementary notes ^EERL project officer is Leslie E. Sparks, Mail Drop 54, 919/
541-2458. Presented at AWMA annual meeting, San Antonio, TX, 6/18-23/95.
16. abstract^.paper discusses a test method for measuring the fractional aerosol fil-
tration efficiency of air cleaners. The method provides a reliable and accurate way
to measure air cleaner fractional efficiencies over the particle diameter size range
of 0.01 to 10 micrometers. (NOTE: The use of air cleaners has moved steadily from
one of protecting equipment (e. g., the heat exchanger in a furnace) to one of protec-
ting people from objectional indoor aerosol particles; e. g., common dust an aller-
gens. This shift has necessitated the development of new test methods for determin-
ing air cleaner filtration efficiency.) The need for a fractional efficiency test comes
from several sources; (l) the growing concern with indoor air quality (IAQ); (2) that
filtration efficiency is often highly particle-size dependent for particles <10 micro-
meters in diameter; (3) limitations of the current American Society of Heating, Re-
frigerating and Air- Conditioning Engineers (ASHRAE) efficiency test which, by de-
sign, cannot differentiate between particle sizes; and (4) that respirable particles
are generally classified as those <10 micrometers in diameter.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution Measurement
Aerosols
Filtration
Ventilation
Air Cleaners
Particles
Pollution Control
Stationary Sources
Particulate
13 B
07 D
13	A
131
14	G
18, DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)

-------