CHAMBER SIMULATION OF FINE PARTICLE PENETRATION INTO HOUSES
R. B. Mosley* and D. J. Greenwell. U. S. Environmental Protection Agency, National Risk
Management Research Laboratory, Research Triangle Park, NC 27711.
ABSTRACT
Exposure to fine particles of outdoor origin has garnered increased interest of late. A number of
recent studies have shown a correlation of negative health effects with increases in outdoor fine
particles. Since people spend up to 90% of their time indoors, the relationship between indoor
and outdoor fine particles has taken on added significance. This paper describes some results
from a study in which the processes of particle removal from infiltrating air by building
envelopes are simulated in a chamber. The chamber consists of two compartments, each having
a volume of 19 m3. Particles with aerodynamic diameters in the range of 0.015 to 5 um are
generated in one compartment and then transported through simulated leakage paths to the other
compartment under the action of applied pressure differentials. The simulated leakage paths
described in this paper consist of horizontal slits (0.508 mm high, 102 mm deep, and 433 mm
wide) between aluminum plates. The penetration factor for each size particle is determined by
simultaneously measuring the concentrations in the two compartments as a function of time. The
penetration factor is obtained through a mathematical solution of the mass balance equations.
The measured values of penetration are compared to predictions of a mathematical model
describing deposition by the mechanisms of settling and diffusion. At applied pressures of 2 Pa,
only 5% of 0.01 um particles and 60% of 0.025 urn particles pass through the 0.508 mm high
slits. At a pressure of 5 Pa, 30% of 0.01 um particles and 80% of 0.025 um particles pass
through the slits. At 10 Pa, 54% of 0.01 urn particles and 90% of 0.025 um particles pass
through the slits. At 20 Pa, 72% of 0.01 urn particles and 94% of 0.025 um particles pass
through the slits.
Key words: penetration, fine particles, filtering, deposition
Introduction
Concern over exposure to fine particles (< 2.5 um in diameter), particularly in the indoor
environment, continues to grow. This concern has resulted in increased interest in understanding
the exposure one obtains indoors to fine particles that originate outdoors. The entry mechanisms
of particles into buildings are not well understood. The sizes and distribution of openings in
building shells are especially unclear. Two recent studies, Thatcher and Layton (1995) and
Ozkaynak et al. (1996), have concluded that the penetration factor for particles with diameters
smaller than 10 um is unity. Thatcher and Layton (1995) performed particle penetration
measurements in a closed, two-story house in California. The entire house was treated as a well-
mixed zone even when analyzing the deposition of particles (1-25 um) resuspended on the first
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floor. Measurements were performed only on the first floor. Penetration of outdoor particles
was ignored during the particle deposition measurements (an assumption that was, at best, valid
only during the very early stage of those measurements). Particle concentrations were
interpreted in terms of mass concentration lumped into rather wide size bands. The paper
concluded that the penetration factor is approximately unity for all particle sizes up to 25 um,
Ozkaynak et al. (1996) reported on a large "Particle Total Exposure Assessment Methodology
(PTEAM)" study performed in Riverside, California. This study reported an average air
exchange rate of 0.97 h"1 and a penetration factor of about unity even for 10 um diameter
particles. This relatively large average value of air exchange rate suggests that many of the
houses may have been operated with windows open, a circumstance that is likely to imply a
penetration factor near unity. The conclusion that the penetration factor is unity seems to imply
that particles enter buildings as easily as the air that carries them. This conclusion is quite
troublesome in light of the usual recommendations for at-risk individuals to stay indoors on days
of poor air quality or when the ambient particle count is high. The question of whether particles
penetrate through the openings in buildings with perfect efficiency plays an important role in
understanding the relationship between outdoor particle concentrations and human exposure to
those particles, especially for individuals who are largely confined to the indoors. However,
since people typically spend the majority of their time indoors, this issue is very important to
everyone's exposure. The majority of the published information about particle penetration
factors has come from the two studies mentioned above. The PTEAM study was not focused on
measuring the penetration factor, but merely tried to statistically tease it out during data analysis.
While the Thatcher and Layton study did focus on penetration, it is a study of about 2 weeks in
only one house and, consequently, is not definitive. While it seems counterintuitive that all
particles, especially the large and very small ones, would readily pass through the small openings
in a building shell, little work has been done to better understand the mechanisms by which
particles are transported into buildings. Lewis (1995) used controlled experiments with well-
defined apertures to demonstrate that penetration of particles with diameters larger than 1 um is a
function of applied pressure and particle size. None of the studies to date, however, address the
penetration of submicrometer-sized particles into the indoor environment. Penetration of
ambient particles to the indoors has important implications for personal PM exposure.
The objective of the present study is to better understand the mechanisms by which outdoor
particles enter the indoor environment. While the study is being conducted at both the
laboratory- and full-scale levels, only the laboratory results are discussed in this paper. The
laboratory study attempts to perform carefully controlled experiments in airtight chambers so
that only particles intentionally injected will be observed in the measurements. In the laboratory,
well-defined geometric shapes that are more easily modeled than those of the real world are used
to simulate the infiltration routes. This paper will report some results with rectangular slits. The
laboratory studies are intended to result in mathematical models that will be validated with well
defined entry routes and have the ability to extrapolate to the non-ideal entry routes associated
with real construction. The results presented here are an extension of a previous study, Mosley
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et al. (2001), which concentrated on the particle size range for which deposition is dominated by
gravitational settling. This study emphasizes particles in the size range for which deposition is
dominated by diffusion.
Chamber Description
The research chamber is illustrated in schematic form in Figure 1. The chamber consists of two
compartments with nearly identical volumes (nominally 19m3 each) separated by a partition
containing a 0.6 x 1.2 m window in which a panel of designed openings (capillary tubes, slits, or
other orifices) is sealed to provide simulated infiltration entry routes of a building. The walls
and ceiling of the compartments are made of gypsum board, while the plywood floors are
covered by linoleum. A great deal of effort was expended to reduce the leakiness of each
compartment. Each compartment has a leak rate of 0.1 h"1 when pressured to 125 Pa. Each
compartment has a ceiling fan that is used to mix the air in the compartment. Since the ceiling
fans in the two compartments are not identical in either size or location, the possibility exists that
the deposition rate constants will differ when the fans are running. Each compartment is
equipped with a high efficiency particle air (HEP A) filter capable of reducing the particle
concentration in that compartment to less than 1000 particles m"3 (detection limit) in about 15
minutes. The air circulation duct is shown on top of the chamber. It contains two in-line fans in
series, a HEPA filter, and a laminar flow measurement section. In order to generate the pressure
difference that drives the airflow through the simulated entry routes, air is extracted from
compartment 2, filtered, and injected into compartment 1. The rectangular slits, simulating
leakage paths, are formed by stacking aluminum plates (3.175 mm thick, 101.6 mm wide, and
521.9 mm long) separated by 0.508 mm thick spacers made of shim stock. A spacer 25.4 mm
wide and 127 mm long was placed at each end. Three additional spacers 12.7 mm wide were
placed at equal distances between the two end spacers. Each slit is then broken into four
segments of about equal length. The four segments represent a single slit with a length of 433
mm. The plates are stacked in a steel frame with long threaded rods used to uniformly compress
the plates against the spacers. While it is very difficult and tedious to measure the variability in
the height of the horizontal slits, it is easy to visually observe that the spacing of the plates
appears quite uniform. The measurements reported here were performed using 140 such slits.
The aluminum plates were purchased with a mill finish (6063 - T5/T52 which corresponds to
Federal Specification QQ-A - 200/9d). A Pitot tube using a Shortridge flow meter as a sensor
measures the flow rate. This flow measurement system was calibrated against both a Roots
meter at high flow rates and a dry gas meter at low flow rates. The calibration curve spans a
range from about 0.001 to 0.04 m3 s"1. The Roots meter had an uncertainty of ± 1.5%, and the
maximum combined uncertainty of the calibration curve for the Pitot/Shortridge combination
was 15%.
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Exhaust
Fan1
HEPA
Filter
Flow
Sensor
. c_> ' Mixing Fan
<-
~^-
4-
Compartment 2
Simulated
Entry Routes
Compartment 1
Figure 1. A schematic of the fine particle measurement chamber.
PROTECTED UNDER INTERNATIONAL COPYRIGHT
ALL RIGHTS RESERVED
NATIONAL TECHNICAL INFORMATION SERVICE
U.S. DEPARTMENT OF COMMERCE
Reproduced from jWfe
best available copy. lyf
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Experimental Methods
The experiments are intended to simulate entry of particles through building envelopes when all
windows and doors are closed. We are studying one well-defined geometric entry route at a
time. The present results are for an array of 140 slits 0.508 mm high, 102 mm deep, and 433 mm
wide. These open slits constitute an effective leakage area of about 30240 mm2 or about 0.03
m2. Compartment 1 of the chamber simulates the outdoors, while compartment 2 simulates
indoor space. The air cleaners are operated to reduce the background concentration in both
compartments to below 1000 m"3 (the detection limit of the instruments). The air cleaner in
compartment 1 is turned off and particles are injected, with the mixing fan running, until the
desired concentration is obtained. The particle concentration is raised to the optimum range of
performance for the measurement instruments. Injection is then stopped and the fan continues
running to ensure good mixing in the compartment. The mixing fan continues to operate during
the experiment except for studies in quiescent air. When the penetration experiment is ready to
start, the air cleaner in compartment 2 is turned off and the circulation fan is turned on at time
zero. The circulation fans, used to generate the driving pressure, are controlled by a variac that
is manually adjusted to yield the specified pressure. Because of the interactions between the two
compartments and the duct with a HEPA filter, it is difficult to maintain a constant pressure
between the two compartments. The setting on the variac is tweaked occasionally to maintain a
constant pressure. Concentrations in both compartments are then monitored as particles are
transported from compartment 1 to compartment 2 by advective flow. Most runs are finished
within 2 hours. In most cases, more than one measurement instrument is used to monitor the
particle concentration. Timed switching valves allow the same instrument to alternately sample
both compartments. As shown in the section on development of equations, the penetration
measurement depends, not on the absolute concentration, but on the ratio of the concentrations in
the two compartments. For this reason, both concentrations used to compute the ratio are
measured with the same instrument. Consequently, the uncertainty in the measured values of
penetration due to bias in the instrument will be reduced when the bias is multiplicative. As a
result, the importance of the absolute accuracy of the individual concentrations is reduced in the
measurement of penetration. The penetration depends on the relative measurements of the two
concentrations. Particles were generated from oil (Emery 3004), incense, or sodium chloride
(NaCl). The oil and NaCl particles were generated with a condensation monodispersed-aerosol
generator.
Data are presented from two particle counters: an electrical low-pressure impactor (ELPI) and a
scanning mobility particle sizer (SMPS). The ELPI is an impactor having 12 collection stages
with mean particle sizes ranging from 0.04 to 8.5 um. This instrument provides real-time
particle size data, as the measurement is based on the current measured on each stage. The
particles pass through a charger and receive a predictable charge before entering the impactor.
Electrometers accumulate the charge collected on each stage, and the number of particles
contacting each stage is computed. Being an impactor, this size measurement also yields an
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aerodynamic diameter. The SMPS uses an electrical classifier to select a very narrow range of
particles sizes that are then counted by a condensation nuclei counter. The classifier is
automatically scanned through a wide range of voltages covering the entire size range from 0.01
to 1 um in particle diameter. This size range can be measured in 60 seconds or less. It is
sensitive to a range 10 6 - 1013 particles m" . The penetration is computed separately for each
instrument. The measured penetration involves simultaneous measurements of particle
concentrations in each compartment of the chamber, as well as a measurement of the air
exchange rate between the compartments.
Equations Used in the Data Analysis
The principle of mass conservation can be applied to the particles in each compartment to obtain
a relationship between the two particle concentrations. A previous study, Mosley et al. (2001),
developed the method for analyzing the data to compute the penetration and deposition rate
constants. Equations (1) and (2) were derived to describe the concentrations as a function of
time in the two compartments:
+ Ks + K\d}t)
C2 (0 = exp(-[^ +K, + K2d ]0( C2 (0)
^CC^O)
V(K2 -Kl
v d d
where Ci (t) is the particle concentration in compartment 1, t is time, Ci(0) is the initial
concentration in compartment 1, Q is the volume rate of air flow between compartments, V is the
volume of each compartment, Ks is the particle decay rate due to gravitational settling, Kid is
the particle decay rate in compartment 1 due to all other deposition processes (primarily
diffusion to the surfaces), €2 (t) is the particle concentration in compartment 2, K2d is the
particle decay rate in compartment 2 due to deposition mechanisms other than settling, €2(0) is
the initial concentration in compartment 2, and P (the penetration factor) is the fraction of
particles leaving compartment 1 by advection that arrive in compartment 2.
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In the development, it was shown that, to a good approximation, the ratio of the two
concentrations reduces to a simple linear function of time provided the experiment does not last
more than an hour or so. That is
(3)
where m is the slope of the resulting linear approximation.
By forming the ratio of the simultaneously measured concentrations in compartments 1 and 2,
the ratio becomes a function that is linear with time. The slope, m (obtained for instance by
linear regression), contains the penetration factor, P. It was shown that the penetration factor is
given by:
p = ——
(Q/V)
(4)
Note that the quantity Q/V is the rate of air exchange between the two compartments.
Models for Particle Deposition in Narrow Slits
Lee and Gieseke (1980) developed Equation (5) to describe the penetration of particles through a
parallel plate channel when deposition is dominated by diffusion:
Pd = e
where Pa is the penetration associated with particle diffusion, D = (kTC) / (3uud) is the
diffusion coefficient, L is the depth of the crack, 2h is the height of the crack, u = Q/(2hw) is the
mean flow velocity, k is Boltzmann's constant, T is absolute temperature, C is the Cunningham
slip correction factor, u is the viscosity of air, d is the diameter of the particle, and w is the length
of the crack.
Fuchs (1964) provides Equation (6) for penetration through a crack resulting from gravitational
settling:
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where Pg is the penetration factor associated with gravitational settling alone, v$ is the settling
velocity, and 2h is the height of the slit. The other parameters are as previously defined. While
inertial deposition was considered in this study, no evidence of this mechanism was observed for
the operating conditions studied. Equations (5) and (6) represent individual mechanisms of
particle penetration. If the two mechanisms are independent of each other, then the combined
effect can be obtained by taking the product:
<* (7)
Equation (7) represents the model predictions that are compared with penetration measurements
in the Results section.
Results
Figure 2 contains three curves that illustrate how the analysis is carried out. The circles
represent the concentration measurements in compartment 1. Note that this concentration decays
exponentially with time. The squares represent the particle concentration in compartment 2. It
starts at zero and increases with time. Both of these concentrations are read on the axis at the left
of the figure. The triangles represent the ratio (C2/Ci) of the two concentrations. This ratio is
read from the axis on the right. The solid line is the linear regression fit to the data. The slope
[m in Equation (4)] of the straight line is shown. This value of slope, along with the appropriate
value of air exchange rate between compartments 1 and 2, is used to compute the penetration
from Equation (7). Similar calculations are performed for each experimental run until a
sufficient database of penetrations as a function of particle diameters is obtained.
Measurements of particle penetration through horizontal slits (0.508 mm high, 102 mm deep, and
433 mm wide) are shown in Figures 3-6. Data from two different instruments, a scanning
mobility particle sizer (SMPS) and an electrical low-pressure impactor (ELPI) are shown. The
continuous line shown in all four figures represents a model prediction. The model predictions
are from Equation (7). In all four figures, the circles represent averages of SMPS measurements
and the squares represent average measurements of the ELPI. The error bars on the individual
data symbols correspond to 1 standard deviation from the average.
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Figure 3 shows results for an applied pressure of 2 Pa. In Figure 3, the model agrees relatively
well with the measurements. Figure 4 shows a similar comparison for the case of 5 Pa applied
pressure. Note that slightly more particles of all sizes penetrate the slits than for the 2 Pa case.
This results because of the higher flow rate associated with the higher pressure. Higher flow
rates correspond to lower residence times for the particles in the slits. Since deposition by both
diffusion and settling depend on residence time, fewer particles deposit. This effect is also
apparent in Figures 5 and 6. In Figure 5 the applied pressure is 10 Pa, which leads to
approximately 70% of the residence time for particles in the slits compared to the 5 Pa case. The
value of penetration increases accordingly. In Figure 6 the pressure is doubled again, resulting in
a residence time that is about 70% of that in Figure 5. There is a corresponding increase in the
penetration for each particle size. Once again the number of particles of a given size that
penetrate through the slits increases.
Discussion
These measurements have attempted to simulate the entry of ambient fine particles into the
indoor environment through horizontal slits 0.508 mm high. The applied pressures (2, 5, 10, and
20 Pa) used as driving forces for the entry process are believed to span the realistic range. A
negative pressure of 2 Pa in a structure is quite common during much of the year in many regions
of moderate climates in the U. S. A negative pressure of 5 Pa in structures is common when the
outdoor temperature is near freezing. Outdoor temperatures at and just below freezing will result
in negative pressures of 10 Pa in many houses. While a negative pressure of 20 Pa would be rare
in moderate climates, it will occur more often in cold climates. A representative set of
measurements is shown in Figure 2. The experiment ran for about 1.8 hours. A linear fit to the
ratio function appears to be quite good during the entire period of the measurements. However,
closer analysis indicates that a slight deviation from linearity begins after about 1 hour. During 1
hour, 30 measurements of concentration are performed in each compartment. This set of
measurements was performed for particles with aerodynamic diameters of 1.6 urn. For some
larger particles, the deviation from linearity of the ratio function may occur as soon as 30
minutes after the experiment begins. In this case, only 15 pairs of measurements are valid for
model analysis. In any event, 15 measurements are probably still adequate for computing an
average slope and, thus, particle penetration.
A simple propagation of measurement errors in Equations (3) and (4) provides general bounds on
the uncertainty of the measured penetration. The manufacturer specifies an accuracy of ± 10%
for particle concentration measurements with the SMPS. As indicated earlier, an uncertainty of
± 15% is associated with the measurement of the flow rate. It follows that the combined
uncertainty in the slope computed from Equation (3) would be ± 20% and the combined
uncertainty in the penetration from Equation (4) would be ± 35%. The measured penetration of
1.16 (16% greater than the maximum allowed value) at 0.205 um in Figure 6 is still within the
35% estimated maximum uncertainty.
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Another potential source of error relates to the assumption that the gas volumes in the two
compartments are well mixed. While definitive measurements to establish a characteristic
mixing time have not been performed, some qualitative observations were made. With the
mixing fan in compartment 1 running on low speed, the injection was suddenly stopped and the
time required for the measured concentration to stop increasing (the sampling port was across the
compartment from the injection port) was observed. In this case, measurements were performed
every 30 seconds and generally the concentration stopped increasing within 10 minutes. For
particles with aerodynamic diameters of 5 urn, the concentration began to decrease almost
immediately after turning the injection off. At the beginning of each experiment, particles in
compartment 1 were allowed to mix (with the fan on low) for 15 to 45 minutes or longer
(depending on the particle size) after turning the injection off and before starting the experiment.
Consequently, compartment 1 was always well mixed. Since measurements in compartment 2
were taken every 3 minutes during normal runs, with the entry process continuous, the volume
may not have been fully mixed. The error due to lack of complete mixing was probably
relatively minor after several measurement cycles. However, the first few measurements
probably have substantial error due to incomplete mixing. The total impact of this experimental
error on the computed slope of the linear curve is reduced by the fact that the curve is forced to
pass through the origin. Consequently, the initial measurements in compartment 2 are less
important than the later ones in determining the slope and, thus, the penetration.
A previous study, Mosley et al. (2001), emphasized the large particle limit of these curves where
the deposition is dominated by gravitational settling. The experimental data presented in that
paper were concentrated at the large particle end of the curves and confirmed the cutoffs
suggested by the model predictions. In that study, it was concluded that only 2% of 2 urn
particles and 0.1% of 5 ^m particles pass through the slits when a pressure of 2 Pa is applied. At
a pressure of 5 Pa, 40% of 2 jim particles and less than 1% of 5 jim particles pass through the
slits. At 10 Pa, 85% of 2 ^m particles and 1% of 5 ^m particles pass through the slits. At 20 Pa,
90% of 2 }im particles and 9% of 5 jim particles pass through the slits. The present study
emphasizes the small particle end of the curves where deposition is dominated by diffusion.
Conclusions
Particle penetration through narrow (0.508 mm high, 102 mm deep, and 433 mm wide)
horizontal slits is a strong function of particle size for applied pressure ranges that are typical of
indoor/outdoor pressure differences (2 - 20 Pa). At an applied pressure of 2 Pa, only 5% of 0.01
\im particles and 60% of 0.025 urn particles pass through the 0.508 mm high slits. At a pressure
of 5 Pa, 30% of 0.01 urn particles and 80% of 0.025 ^m particles pass through the slits. At 10
Pa, 54% of 0.01 \im particles and 90% of 0.025 ^m particles pass through the slits. At 20 Pa,
72% of 0.01 urn particles and 94% of 0.025 ^m particles pass through the slits.
10
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References
Fuchs, C.N,. (1964). The Mechanics of Aerosols. Pergamon Press, New York, NY.
Lee, K.W., and Gieseke, J.A., (1980). Simplified Calculation of Aerosol Penetration Through
Channels and Tubes. Atm. Env., 14:1089-1094.
Lewis, S., (1995). Solid Particle Penetration into Enclosures. J. Haz. Mat., 43:195-216.
Mosley, R.B., Greenwell, D.J., Sparks, L.E., Guo, Z., Tucker, W.G., Fortmann, R., and
Whitfield, C., (2001). Penetration of Ambient Particles into the Indoor Environment. Aerosol
Sci. Tech. 34:127-136.
Ozkaynak, H., Xue, J., Spengler, J.D., Wallace, L.A., Pellizzari, E.D., and Jenkins, P., (1996).
Personal Exposure to Airborne Particles and Metals : Results from a Particle TEAM Study in
Riverside, CA. J. Expos. Anal, and Environ. Epidem. 6(l):57-78.
Thatcher, T.L., and Layton, D.W., (1995). Deposition, Resuspension, and Penetration of
Particles Within a Residence. Atm. Env., 29:1487-1497.
11
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120
100
E 80
u
c
o
*3
ra
60
u
§ 40
o
20
Compt 1 Cone
Compt2 Cone
Ratio
Linear (Ratio)
y = 0.3769x
R2 = 0.9943
0.8
0.6
o
0.4 I
0.2
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Time (h)
Figure 2. A typical set of concentration measurements in both compartments of the chamber for an Emery oil particle with
aerodynamic diameter of 1.6 ^,m. The ratio of concentrations is also shown to illustrate the method of computing
penetration under an applied pressure of 5 Pa.
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* SMPSData
—Model
0 +-4r
0.01
0.10 1.00
Aerodynamic Diameter (p.m)
10.00
Figure 3. Comparison of penetration measurements and model predictions for 2 Pa pressure applied across 0.5 x 102 mm
horizontal slits.
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ELPI Data
SMPS Data
Model
0.01
0.10 1.00
Aerodynamic Diameter (v m)
10.00
Figure 4. Comparison of penetration measurements and model predictions for 5 Pa pressure applied across 0,5 x 102 mm
horizontal slits.
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il*
m ELPIData
* SMPSData
— Model
_J - ™- - 1
1 - 1 - 1 - L_
-4;v;v;v; v;;v; ' J L_
0.01
0.10 1.00
Aerodynamic Diameter (urn)
10.00
FigureS. Comparison of penetration measurements and model predictions for 10 Pa pressure applied across 0.5 x 102 mm
horizontal slits.
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ELPIData
« SMPSData
—•Model
0.01
0.10 1.00
Aerodynamic Diameter (jam)
10.00
Figure 6. Comparison of penetration measurements and model predictions for 20 Pa pressure applied across 0.5 x 102 mm
horizontal slits.
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NRMRL-RTP-P-598
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA7600/A-01/038
2.
3, RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Chamber Simulation of Fine Particle Penetration
into Houses
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
R. B. Mosley and D« J. Greenwell
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING OROANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO,
See Block 12
11. CONTRACT/GRANT NO.
68C99201-008
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper; l/OQ-3/01
14. SPONSORING AGENCY CODE
EPA/600/13
15.SUPPLEMENTARY NOTES APPCD project officer is Ronald B. Mosley, Mail Drop 54, 919/
541-7865. Presented at American Filtration Society Meeting, Tampa, FL, 5/1-4/01.
16. ABSTRACT ,
The paper discusses chamber simulation of fine particle penetration into
houses. (NOTE: A number of recent studies have shown a correlation of negative
health effects with increases in outdoor fine particles. Since people spend up to 90%
of their time indoors, the relationship between indoor and outdoor fine particles has
taken on added significance.) The paper describes some results from a study in
which the processes of particle removal from infiltrating air by building envelopes
are simulated in a chamber, consisting of two compartments, each with a volume of
19 cu m. Particles with aerodynamic diameters in the range of 0.015 to 5 micro-
meters are generated in one compartment and then transported through simulated
leakage paths to the other compartment under the action of applied pressure differ-
entials. The simulated leakage paths consist of horizontal slits between aluminum
plates. The penetration factor for each size particle is determined by simultaneous-
ly measuring the concentrations in the two compartments as a function of time. The
penetration factor is obtained by mathematically solving the mass balance equations.
The measured value of penetration are compared to predictions of a mathematical
describing deposition by the mechanisms of settling and diffusion.
17.
KEY WORDS AND DOCUMENT ANALYSIS
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b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Particles
Simulation
Test Chambers
Filtration
Residential Buildings
Pollution Control
Stationary Sources
Fine Particles
Deposition
Indoor Air
Particulate
13B
14G
14B
07D
13M
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