United States
Environmental Protection
Agency
Air and Energy
Engineering Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-88/098 Jan. 1989
&EPA Project Summary
Follow-Up Alpha-Track
Monitoring in 40 Eastern
Pennsylvania Houses with
Indoor Radon Reduction
Systems (Winter 1987-88)
Arthur G. Scott and Andrew 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
reduction in indoor radon concen-
trations achieved in each house was
described in an earlier report.
The purpose of the current study
was to make follow-up alpha-track
detector (ATD) measurements of
radon concentrations in these
houses, approximately one year after
the last of the installations was
completed, in order to determine
how well the radon reduction per-
formance of the systems was being
maintained. The ATD measurements
were made over a 3-month period
during the winter (December 1987-
March 1988), to assess system
performance when cold weather
would be giving the systems a
significant challenge. These 1987-88
ATD results are compared with
comparable post-mitigation ATD
measurements made during the
previous winter (1986-87), 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
1988 compared well with those
measured in 1987 (or any differences
appeared explainable) in all but one
house, indicating no significant
degradation in system performance:
in House 10, an exterior drain tile
suction installation), levels had
increased 50-70% from those
measured in 1987, with no apparent
reason. The well water radon
removals achieved by the carbon
adsorption units appeared not to
have degraded since the previous
water measurements.
Of the 34 houses having operating
active soil systems, two have
experienced fan failure or need for
fan maintenance in the 1-2 years
that the fans have been in operation.
This Project Summary was devel-
oped 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 USEPA is conducting a program to
develop and demonstrate cost-effective
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 picoCunes per liter (pCi/L), or 740
Becquerels per cubic meter (Bq/m3).
These houses had substructures repre-
sentative of the region - basements
having block or poured concrete foun-
dation walls, sometimes with an adjoining
slab-on-grade or crawl space wing.
Active soil ventilation systems, utilizing a
fan - sub-slab suction, drain tile suc-
tion, or block wall suction or pres-
surization - were tested in most of the
houses. Heat recovery ventilators were
tested in three houses having only
moderate radon elevations, and carbon
treatment of well water was tested in two
houses. The installations in these 40
houses, and the initial system perform-
ances, were reported in an earlier report.
To test the durability of these instal-
lations, 3-month ATD measurements of
radon concentrations were made
between December 1987 and March
1988 in the 38 of the 40 houses still
having operating systems. Winter was
chosen for this measurement to
determine system performance when the
system was facing the challenge of cold
weather.
Of the two houses no longer having
operating systems, one was moved from
its original site after the system was
installed; and the owner decided to
discontinue participation in the project.
Measurement Procedures
The measurements were made using
Terradex "Type SF" Track Etch ATDs. In
each house, a cluster of 3 ATDs were
hung together from a central floor joist in
the basement; a second cluster of 3 was
hung in the living area (the story above
the basement), from an interior wall or
ceiling. Clusters of three were used to
reduce measurement uncertainties and
facilitate identification of outliers. The
exposed detectors were returned to the
Terradex laboratories for analysis.
The detectors were deployed in
December, and retrieved in March, by an
experienced professional.
For quality assurance, 14 unexposed
detectors were returned to Terradex as
blanks, to determine the zero correction.
Also, 13 detectors were exposed to
known radon environments in a test
chamber for selected durations, 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 one house, the fan had failed during
the period; and in the other three, the
owner had turned the fan off while on
vacation. 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 con-
centrations listed in the column "1988"
are from this 1987-88 measurement
effort; each number (for the basement
and for the living area) is the average of
the three ATDs in the cluster. Results are
also shown for comparable post-
mitigation ATD measurements during the
previous winter ("1987"); most of the
1987 measurements were made between
December 1986 and March 1987,
although some began later (due to the
installation schedule) and extended into
April. Results are also shown for post-
mitigation measurements 2 years before
("1986"), where available. Premitigation
results, usually from an ATD measure-
ment during an earlier heating season,
are also shown for each house
Comparison of the 1988 and 1987
radon levels indicates that concentrations
have remained fairly steady in most
houses during the year between the two
measurements. Thus, the performance of
the radon mitigation systems does not
generally appear to be degrading. One
house where a degradation is apparent is
House 10, which has a draintile suction
system; radon levels in this house have
increased progressively since the 1986
measurement. Increases between 1987
and 1988 are also apparent in Houses 18
(a heat recovery ventilator) and 25 (a
sub-slab suction system). Part of the
increase in these houses could be
because the 1987 measurements in
these two houses were made between
February or March 1987 and April 1987;
these 1987 readings might be biased low
since more of the measurement period
could have included mild weather.
Radon concentrations were measured
in the well water of House 30, entering
and leaving the carbon treatment unit.
Water concentrations were being
reduced from 83,400 to 3,320 pCi/L (3.1
to 0.12 MBq/m3) for 96% removal,
consistent with the 95-99% removals
measured on a number of occasions
since the carbon unit was installed in
August 1986. Thus, the performance
this unit does not appear to I
degrading.
Fans in 2 of the 34 houses with acti
soil ventilation installations (Houses 2 a
4) have failed or needed repair in the
2 years that they have been operating.
Overall conclusions from an earl
report still appear valid. Reductions
90-99 + % are still being achieved w
the active soil ventilation systems. H<
recovery ventilators give lower, le
predictable reductions, usually no grea
than about 50%; the apparent reducti
of about 80% in House 28 is question!
since the ventilator gave reductions
only 15-45% during short-term bai
to-back measurements with the vei
lator on and off. Carbon filtration c
remove 95-99% of the radon in wa
at least over the 16-month test per
here.
-------
Table 1. Summary of Results to Date for Houses with Mitigation Fans Operating Throughout the 1988 Measurement Period
Average Rn (pCi/L)
Post-Mitigation"*
House
No.
3
5
6
7
8
9
10
12
13
14
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
House
Type"
1
1
1
1
1
1
1
1
1
1
2
1
1
1
2
1
3
3
4
4
1
1
1
5
1
1
1
4
Final
Mitigation System
Wall + sub-slab suction
Wall pressurization
Sub-slab suction
Sub-slab * wall suction
Wall suction
Wall + sub-slab
pressurization (baseboard
duct Over French drain)
Drain tile suction (exterior)
Drain tile suction (exterior)
Sub-slab + drain tile
suction (exterior)
Wall suction
Wall suction
Heat recovery ventilator
Heat recovery ventilator
Wall suction
Sub-slab + wall suction,
•* suction under slab in
crawl space
Sub-slab suction
Sub-slab suction
(basement * slab)
Sub-slab suction
(basement + slab)
Sub-slab suction
Sub-slab suction
Drain tile suction (exterior)
Drain tile suction (exterior)
Heat recovery ventilator
Drain tile suction (interior
sump) + suction under
crawl space line
Carbon adsorption
treatment of well water
Sub-slab suction
Sub-slab suction
Sub-slab suction
Average Rn
(pCi/L)~
Pre-Mitigation
350
(110)
60
(402)
183
533
626
(11)
64
36
395
9
12
32
210
172
24
98
66
122
(89>
21
21
61
17
(485)
(6)
82
1988
B
3.5
5.0
4.1
4.9
3.5
10.4
15.2
2.2
2.6
1.1
5.7
8.2
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
2.8
1.2
3.5
LA
2.3
4.4
3.2
3.8
1.5
12.9
9.9
2.2
3.9
1.4
2.5
6.4
3.4
0.8
10.0
2.7
4.4
16
3.8
6.0
1.6
2.2
4.4
2.0
1.6
8.3
4.4
1.2
1987
B
3.5
4.3
3.3
4.1
3.9
11.6
9.0
3.7
23
05
5.4
7.6
8.8
32.0
5.8
3.1
7.6
—
4.3
5.4
2.1
3.8
2.4
1.9
3.0
1.8
1.0
2.2
LA
2.1
43
4.9
2.8
1.8
14.5
6.5
2.5
2.0
0.7
1.7
4.1
2.1
0.6
9.9
2.6
2.7
—
4.6
3.0
1.5
2.2
5.3
1.4
1.3
5.7
3.2
1.1
1986
B LA
4.4 1.7
- -
- -
- -
3.1 1.3
— —
3.3 3.0
- -
— _
0.7 0.6
_ _
- -
- -
- -
— —
- -
— —
— —
- -
- —
- -
- —
_ _
— —
_ _
- -
_ _
_ _
-------
Table 1. (Continued)
Average Rn (pCUL)
Post-Mitigation""
House
No.
34
35
36
37
38
40
House
Type"
4
4
3
3
1
4
Final
Mitigation System
Sub-slab suction
Sub-slab suction
Sub-slab suction
(basement + slab)
Sub-slab suction
(basement only)
Sub-slab suction
Sub-slab suction
Average Rn
(pci/tr
Pre-Mitigation
470
144
300
87
309
148
1988
B
54
1.0
1.1
1.2
8.7
1.9
LA
5.5
0.9
1.0
0.7
7.2
1.2
1987
B LA
5.5 3.7
0.8 0.7
1.6 0.7
0.6 1.7
- —
— —
1986
B LA
- -
- -
— —
— —
— -
- -
"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 Track Etch 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 (e.g., was inside a sump), or where the ATD result is 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 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 three alpha-track detectors
exposed 3 months during the winter: 1988 measurements were made during this study (December 1987 - March 1988): 1987
measurements were generally made between December 1986 and March 1987: and 1986 measurements were generally made
between December 1985 and March 1986. All results are modified for gain and zero correction. Absence of figures for 1986
or 1987 for a given house indicates that: ATD measurements were not made in that house that winter: or the radon mitigation
system was changed significantly between that and the following winter: or the ATD measurement was made significantly
outside the December - March window due to the system installation schedule. B = Track Etch measurements in the
basement. LA = Track Etch measurements in the living area (story above basement).
-------
Arthur G. Scott and Andrew Robertson are with American ATCON, lnc.;~
Wilmington, DE 19899.
D. Bruce Henschel is the EPA Protect Officer (see below).
The complete report entitled, "Follow-Up Alpha-Track Monitoring in 40 Eastern
Pennsylvania Houses with Indoor Radon Reduction Systems (Winter 1987-
88)," (Order No. PB 89-110 035/AS; Cost: $13.95) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Protect 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/S8-88/098
0000329 PS
0 S ENVIR PROTECTION AGENCY
REGION 5 LIBRARY
230 $ DEARBORN STREET
CHICAGO IL 60604
------- |