1 November 1996
11. POST CONSTRUCTION RADON MITIGATION. When post construction radon measurements are
greater than 4 pCi/L, mitigation systems designed into the facility will be activated incrementally until the
radon level is reduced to less than 4 pCi/L. The incremental steps are as follows:
a. Activate sub-slab suction systems or power ventilate crawl spaces.
(1) Install passive vent stack(s) to sub-slab systems for low and moderate radon levels. If
subsequent radon measurements are greater than 4 pCi/lL, then install exhaust fans for active vent stack.
(2) Install active vent stack(s) with exhaust fans for high and very high radon levels.
b. Increase interior positive air pressure.
c. Increase the outside-air exchange rate.
12. DESIGN DETAILS.
a. Design details are included in appendix A. The design details are generic in nature to depict a
variety of typical conditions that are adaptable to specific building designs. Some details may not be
applicable to every building; unique conditions are not included. Each detail and/or portions thereof are
identified with letter codes that relate to table 1. Additional design guidance may be found in ASTM E 1465
and the EPA publications listed in the references.
b. Reinforcing for concrete and masonry construction shall be provided according to specific design
requirements and is not indicated in the details. Minimum reinforcement to control shrinkage cracks in
concrete slabs on grade will be 6x6-w1.4xw1.4 welded wire fabric.