ETL 1110-3-438
15 SEP 93
according to air flow and pressure losses due to pipe length and
number of turns.
(6) Fan Selection. The fan selected will have cfm and horse
power ratings adequate to maintain 1 inch wc static pressure at the
slab penetration under constant operation. This will be mounted
directly in or to the vertical riser with air tight connections and
will be of such design that condensation of soil gas moisture will
drain either back down the stack or onto the roof. Fans may be an in-
line configuration and installed in the stack or a standard curb
mounted exhaust fan.
(7) Naturally Ventilated Buildings. Naturally ventilated
buildings that are neither heated or cooled by mechanical systems and
are in any of the facility priorities 1 through 4 will be designed to
include passive barriers (letter code A) only.
POTENTIAL
RADON CONCENTRATION
FOR
NEGLIGIBLE LOW
MODERATE
HIGH
VERY HIGH
FACILITY 0 TO
4 TO8
8 TO
20 TO
Over
TYPES
4pCi/1
pCi/l
20 pCi/l
200 pCi/l
200 pCi/l
A
A,B
A,C
1
A,D,E
A,D,F
A
A,B
A,B
2
A,D,E
A,D,F
A
A,B
A,B
3
A,C
A,D,E
A
A
A
4
A,B
A,C
TABLE 1. DESIGN REQUIRMENTS FOR RADON PREVENTION
b. Existing Buildings. Radon mitigation requirements
incorporated into the design of building alterations will be based
upon the facility priority and actual radon measurements in the
building. The design requirements in Table 1 will be evaluated
according to life cycle cost/benefit analysis and engineering
judgment. For example, removal of slab-on-grade floors to install a
sub-slab suction system may not be cost effective when compared to
the differential in equipment and operating costs to increase
interior air pressure or the outside-air exchange rate.
10. POST CONSTRUCTION RADON MEASURE:
a. After completion of construction, indoor radon measurements
will be made with all HVAC systems operating on normal cycles.
Radon detectors and laboratory analytical services will be obtained
through U.S. Army Center for Pubilc Works. Ft. Belvoir. Virginia
22060-5516.
b. The severity of potential. indoor radon concentration cannot
be accurately predicted. The time duration for post construction
radon measurements and the extent of mitigation work that may be
5
A-7
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