United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-89/083 Jan. 1990
Project Summary
Follow-up Alpha-Track
Monitoring in 40 Eastern
Pennsylvania Houses with
Indoor Radon Reduction
Systems (Winter 1988-89)
A. G. Scott and A. Robertson
Between June 1985 and June 1987,
developmental indoor radon reduc-
tion systems were installed in 40
houses in the Reading Prong region
of eastern Pennsylvania. Most of
these systems involved some form of
active soil ventilation, although three
involved heat recovery ventilators
and two included carbon filters for
removing radon from well water. The
Initial reductions in indoor radon
concentrations achieved in each
house were described earlier. Follow-
up alpha-track detector (ATD) meas-
urements of radon concentrations in
these houses during the winter of
1987-88 were also described earlier.
The purpose of the current study
was to make follow-up ATD measure-
ments in these houses over the
Winter of 1988-89, two to four years
after the installations were com-
pleted, in order to further determine
how well the radon reduction
performance of the systems was
being maintained. The ATD measure-
ments were made over a 4-month
period during the winter (December
1988 - early April 1989), to assess
system performance when cold
weather would be giving the systems
a significant challenge. These 1988-
89 ATD results are compared with
comparable ATD measurements
made during the two previous winters
and with those made prior to the
installation of the radon reduction
system.
Of the 34 houses where the radon
mitigation system was In operation
during the entire measurement
period, the radon levels measured in
1989 compared well with those
measured in prior years (or any
differences appeared explainable) in
all but two of the houses. In those
two houses, concentrations in the
basement had increased by 220 to
360% for no apparent reason, probab-
ly because the system performance
had been marginal. Well water radon
removal was maintained at 97% at the
one house that had a charcoal unit
designed specifically for radon, but
had fallen to 65% at the house with a
general-purpose charcoal unit.
Two additional soil ventilation fans
failed during the past year, bringing
to five the number of fan failures over
two to four years of operation in the
34 houses having operating active
soil ventilation systems.
This Project Summary was
developed by EPA's Air and Energy
Engineering Research Laboratory,
Research Triangle Park, NC, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The U.S. Environmental Protection
Agency (EPA) is conducting a program to
develop and demonstrate cost-effective
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methods for reducing the concentrations
of naturally occurring radon gas inside
houses. As part of this program, EPA
sponsored the installation of develop-
mental radon reduction measures in 40
existing houses in eastern Pennsylvania
having high initial radon levels - above 20
picocuries per liter (pCi/f), or 740 Bec-
querels per cubic meter (Bq/m3). These
houses had substructures representative
of the region - basements having block
or poured concrete foundation walls,
sometimes with an adjoining slab-on-
grade or crawl-space wing. Active soil
ventilation, utilizing a fan - sub-slab
suction, drain tile suction, or block wall
suction or pressurization - was tested in
most of the houses. Heat recovery
ventilators (air-to-air heat exchangers)
were tested in three houses having only
moderately elevated radon levels, and
charcoal treatment of well water was
tested in two houses. The installations in
these 40 houses and the initial system
performances were reported earlier.
To test the durability of these
installations, 3- to 4-month ATD measure-
ments of radon concentrations have been
made during the winter periods since the
installations were completed, Measure-
ments during the winter of 1987-88 were
reported earlier; measurements during
the winter of 1988-89 are reported here.
Winter was chosen for this measurement
to determine system performance when
the system was facing the challenge of
cold weather.
The measurements reported here
were completed in the 38 of the 40
houses which still have operating sys-
tems. Of the two houses no longer having
operating systems, one was moved from
its original site after the system was
installed; in the other, the owner decided
to discontinue participation in the project.
Measurement Procedures
The measurements were made using
Terradex Type SF Track Etch alpha-track
detectors (ATDs). In each house, two
ATDs were hung together from a central
floor joist in the basement; a second pair
was hung in the living area (the story
above the basement) from an interior wall
or ceiling. Pairs were used to permit
identification of outliers.
The detectors were deployed in mid-
December and retrieved in early April by
an experienced professional. The ex-
posed detectors were returned to the
Terradex laboratories for analysis.
For quality assurance, seven unex-
posed detectors were returned to
Terradex as blind blanks, to determine
the zero correction. Also, 10 detectors
were exposed to known radon
environments in a test chamber for a
selected duration, and returned to
Terradex as blind spikes, to determine
the gain correction.
Results and Discussion
Of the 38 houses in which ATDs were
deployed, it was found upon retrieval of
the detectors that the mitigation system
fans had been off in four houses during
some portion of the measurement period.
In two houses, the soil ventilation fan
failed; in a third house, the soil ventilation
fan had been inadvertently unplugged;
and in the fourth house, the fan motor in
a heat recovery ventilator failed. Thus, in
only 34 houses do the ATD results give
radon concentrations representative of
uninterrupted system operation.
The results from these 34 houses are
presented in Table 1. The radon concen-
trations listed in the column "1989" are
from this 1988-89 measurement effort;
each number (for the basement and for
the living area) is the average of the
paired ATDs. Results are also shown for
comparable post-mitigation ATD mea-
surements during the previous two
winters ("1988" and "1987"). Where
available, results are also shown for post-
mitigation measurements 3 years before
("1986"). Pre-mitigation results, usually
from an ATD measurement during an
earlier heating season, are also shown for
each house.
An analysis of the data in Table 1
indicates that the mean heating season
radon concentration measured in 1989 is
similar to that measured the previous
year for almost all houses, indicating no
overall degradation in system perfor-
mance. Of the 34 houses in the table, 16
have 1989 ATD results, both in the
basement and upstairs, which vary from
the 1988 results by less than 1 pCW; in
24 of the houses, no one result varies by
more than 2 pCi/f from 1988. Considering
the variability of radon levels in houses,
and the accuracy of the measurement
method, this agreement suggests no
degradation within our ability to measure.
Of the 24 houses in Table 1 which
changed by less than 2 pCi/f, most
(58%) decreased in radon level. The fact
that such a large percentage decreased
in concentration could be partially due to
the fact that, in 1989, the measurement
period extended to early April, thus
encompassing an additional 2 weeks of
possibly mild weather compared to the
1988 period, which extended only to late
March. Also, the 1988/89 winter was
reported by the homeowners to hav«
been relatively mild.
Of the 10 houses, where either th<
upstairs or basement levels changed b<
2 pCi/l or more: in three houses (House:
4, 15, and 39), levels dropped dramal
ically in 1989 because the mitigatioi
system had been off for part or all of thi
1988 measurement period; in two othe
houses (Houses 10 and 19), level
decreased by about 5 pCi/f for unknowi
reasons, reflecting the variability of th
system and the house dynamics; in thre
houses (Houses 2, 9, and 22), level
increased by 2.0 to 4.2 pCi/J (an increas
of 25 to 32%), either due to systerr
house dynamics variability or perhap
due to some limited degradation; and i
the final two houses (Houses 33 and 40
there was a significant increase in rado
levels in the basements (by 220% i
House 33, by 360% in House 40
sufficiently large to suggest that som
real degradation had in fact occurred.
Houses 33 and 40 have largi
unexplained increases in the basemei
which possibly suggest some degradi
tion. In both these houses, radon upstai
did not increase nearly so dramatically.
fact, in House 33, the upstairs coi
centration went down. House 33 was
small basement house with poure
concrete foundation walls and r
adjoining living wing. Suction is drawn <
a concrete-lined, concrete-bottom sun
pit having no drain tiles; holes we
drilled through the concrete walls of tl
pit to provide access to the sub-sla
While communication under the slab h
not yet been measured, diagnosl
smoke stick testing after installation
the system had suggested that tl
distribution of the suction under the si
was ambiguous. Thus, one possit
explanation for the observed increase
that the system might have be
marginal to begin with, and somethi
happened prior to or during this particu
measurement period to reduce syste
effectiveness, increasing radon from I
pCi/* in 1988 to 11.2 pCi/f in 191
House 40 was a very large basenru
house with poured concrete walls, havi
multiple slab pours and extremely pi
sub-slab communication. Twenty si
slab suction pipes penetrate the slab <.
connect to a single Kanalflakt K6 f
most of the 20 pipes have soil gas flc
of less than 1 cfm (0.5 Us). Although
system has many suction pipes, it n
be marginal due to the very pi
communication, and this could be
explanation for the increase in basem
concentrations from 1.9 pCi// in 198E
8.8pCi/f in 1989.
-------
With two fan failures this year, fans
lave now failed in five of the 34 houses
with active soil ventilation systems over
an operating period of two to four years.
Failure has usually been due either to
bearing failure, or to failure of the
capacitor. All of the failed fans have been
(or are being) replaced under warranty.
The failure of the fan motor in the heat
recovery ventilator this year is the first
failure among the three heat recovery
ventilators installed under this project;
this unit has been repaired.
Radon concentrations were measured
in the well water at Houses 2 and 30,
entering and leaving the charcoal
treatment unit. In House 30, water
concentrations were being reduced from
156,000 pCi// to 4,360 pCi/f (from 5.77 to
0.16 MBq/m3), for a removal efficiency of
97%, consistent with the removals being
achieved when the unit was first installed
over 2 years previously. Thus, there was
no apparent degradation in the
performance of this unit, which contains a
charcoal specifically selected for radon
removal. However, in House 2, water
concentrations were being reduced from
57,200 to 19,900 pCi/* (2.12 to 0.74
MBq/m3), a removal of only 65%; this
represents a continuing degradation from
the removals of up to 95% observed
mmediately after installation two years
previously. This unit was not designed
specifically for radon removal but was
being marketed for organics removal.
Overall earlier conclusions still appear
to be valid. Reductions of 90-99 + % are
still being achieved with the active soil
ventilation systems. Heat recovery
ventilators give lower, less predictable
reductions, usually no greater than about
50%; the apparent reduction of about
80% in House 28 is questioned, since
this ventilator gave reductions of only 15-
45% during short-term back-to-back
measurements with the ventilator on and
off. Carbon filtration can remove 95-99%
of the radon in water, at least over this
28-month test period, if the charcoal is
appropriately selected for radon removal.
-------
Table 1. Summary of Results to Date for Houses with Mitigation Fans Operating Throughout the 1989 Measurement Period
Average Radon Concentration (pCi/l)
Post-Mitigation"*
House
/D#
2
3
4
5
6
8
9
10
12
13
15
16
18
19
20
21
22
23
24
25
26
27
28
29
30
32
33
34
35
36
37
38
39
40
Type"
1
1
1
1
1
1
1
1
1
1
1
2
1
1
2
1
3
3
4
4
1
1
1
5
1
1
4
4
4
3
3
1
1
4
Final System
Wall + sub-slab pressurization
(baseboard duct) + carbon adsorption
on well water
Wall * sub-slab suction
Sub-slab suction
Wall pressurization
Sub-slab suction
Wall suction
Wall + sub-slab pressurization
(baseboard duct)
Drain tile suction
Drain tile suction
Sub-slab suction + drain tile suction
Drain tile suction
Wall suction
Heat recovery ventilator
Wall suction
Sub-slab * wall suction, + suction
under crawl space slab
Sub-slab suction
Sub-slab suction (basement * slab)
Sub-slab suction (basement •*• slab)
Sub-slab suction
Sub-slab suction
Drain tile suction
Drain tile suction
Heat recovery ventilator
Drain tile suction (interior sump)
* suction under crawl space liner
Carbon adsorption treatment of
well water
Sub-slab suction
Sub-slab suction
Sub-slab suction
Sub-slab suction
Sub-slab suction (basement * slab)
Sub-slab suction (basement only)
Sub-slab suction
Sub-slab suction
Sub-slab suction
Pre-
Mitigation"
413
350
25
(110)
60
183
533
626
(11)
64
(18)
395
12
32
210
172
24
98
66
122
(89)
21
21
61
17
(S)
82
470
144
300
87
309
111
148
1989
B
5.5
3.0
1.2
5.0
3.2
2.9
12.4
10.4
1.6
2.7
1.3
4.8
12.7
28.5
8.3
1.9
10.8
2.4
4.3
7.2
0.6
5.6
3.6
2.1
3.9
0.5
11.2
5.1
2.4
0.8
0.9
7.0
7.5
8.8
LA
8.7
1.9
1.0
4.4
2.7
1.0
17.1
8.9
2.1
2.8
1.3
1.1
5.1
0.6
9.3
2.7
4.0
1.5
3.7
5.3
1.1
2.1
5.1
2.3
2.1
3.2
0.7
5.5
1.0
0.7
0.5
7.3
1.8
2.5
1988
B
4.8
3.5
7.3
5.0
4.1
3.5
10.4
15.2
2.2
2.6
19.7
5.7
13.5
33.5
6.5
2.0
8.6
2.6
3.6
7.7
1.1
4.0
4.1
1.6
4.0
1.2
3.5
5.4
1.0
1.1
1.2
8.7
46.1
1.9
LA
6.7"
2.3
3.1 *
4.4
3.2
1.5
12.9
9.9
2.2
3.9
11.0s
2.5
3.4
0.8
10.0
2.7
4.4
1.6
3.8
6.0
1.6
2.2
4.4
2.0
1.6
4.4
1.2
5.5
0.9
1.0
0.7
7.2
17.5a
1.2
1987 1986
B
2.6
3.5
0.7
4.3
3.3
3.9
11.6
9.0
3.7
2.3
1.1
5.4
8.8
32.0
5.8
3.1
7.6
-
4.3
5.4
2.1
3.8
2.4
1.9
3.0
1.0
2.2
5.5
0.8
1.6
0.6
-
-
-
LA B
5.2
2.1 4.4
0.8
4.3
4.9
1.8 3.1
14.5
6.5 3.3
2.5
2.0
1.0
1.7
2.1
0.6
9.9
2.6
2.7
-
4.6
3.0
1.5
2.2
5.3
1.4
1.3
3.2
1.1
3.7
0.7
0.7
1.7
-
-
-
LA
'
1.7
-
-
-
3.1
-
3.0
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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Table 1. Notes
House Type:
1 = Block basement walls
2 = Block basement walls * paved crawl space
3 = Poured concrete basement walls •*• slab on grade
4 - Poured concrete basement walls
5 = Block basement walls + unpaved crawl space
Pre-mitigation radon concentrations reported here represent a single Terradex alpha-track detector
measurement arranged by the Pennsylvania Department of Environmental Resources during a heating
season prior to installation of EPA's radon mitigation system. Where it is known that the pre-mitigation
ATD was not placed in a representative location, or where the ATD result was clearly not representative
of subsequent Pylon measurements made by EPA, the pre-mitigation concentration shown here is the
average of at least 48 hours of hourly radon measurements made in the basement during cold weather
using a Pylon AB-5 continuous radon monitor. Where Pylon measurements have been used, the pre-
mitigation value is shown in parentheses. The Pylon measurements were made during the 1985-87
system installation period.
"" Post-mitigation radon concentrations reported here represent the average of clusters of two or three
alpha-track detectors exposed for a 3- to 4-month period during the winter. 7989 measurements were
made during this study (December 1988 - April 1989). 1988 measurements made during the period
December 1987 - March 1988; 1987 measurements generally made during the period December 1986 -
March 1987; 1986 measurements generally made during the period December 1985 - March 1986. All
results corrected for gain and zero where needed.
a A superscript "a" indicates that the ATD measurements in that house during that year are not
representative of an operating mitigation system, because the system was off for part or all of the
measurement period.
Absence of results for 1986 or 1987 for a given house indicates that: alpha-track measurements were
not made in that house that winter; or the radon mitigation system was changed significantly between
that winter and the following winter; or the alpha-track measurement was made significantly outside the
December - March window due to the system installation schedule.
B » Track Etch measurements in basement
LA = Track Etch measurements in living area (story above basement)
-------
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A. G. Scott and A. Robertson are with American Atcon, Inc., Wilmington, DE
19899
D. Bruce Henschel is the EPA Project Officer (see below).
The complete report, entitled "Follow-up Alpha-Track Monitoring in 40 Eastern
Pennsylvania Houses with Indoor Radon Reduction Systems (Winter 1988-
89)," (Order No. PB 90-134 1721AS; Cost: $15.00, subject to change) will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S8-89/083
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