Radon Reporter March 2022

16 | Mach 2022 MITIGATION The initial radon level of a single-family one-story 1800 ft 2 newly constructed home near the coastline of Massachusetts was 6.5 pCi/l in May 2016. It has a poured concrete wall basement with sand gravel mix under the slab, and an adjoining two-car garage slab. The HVAC system in the mostly unfinished 1653 ft 2 basement is gas-fired hot air with central air conditioning. The 1653 ft 2 basement is unfinished except for a 200 ft 2 finished workroom. In June 2016, a certified company installed a single suction point into the basement slab with a GP501 fan. The post-mitigation test in August 2016 was 4.9 pCi/l. After four additional tests ranging from 3.9 to 5.7 pCi/l, the contractor installed another basement sub-slab suction and sealed the perimeter. A long-term follow-up test in 2017 was 4.2 pCi/l. In March 2021, the mitigator changed the fan to a high-capacity RN4EC3 and added a third basement suction. The radon levels came back at 7.8 pCi/l. The owner then purchased a Radon Eye monitor and observed radon levels averaging around 11 pCi/l. Increasing fan speed did not lower radon levels. The homeowner then contacted the radon hotline, which connected him to Fantech engineer Hamid Massali, who suggested concrete or the garage sub-slab may be the source. In May 2021, the mitigator installed a garage suction, but it produced no additional radon reduction. At this point, the mitigation contractor gave up on the house and returned the money he had charged for the additional work. With help from hotline advisors and a borrowed micro- monometer, the homeowner measured the basement sub-slab as negative 25 to 50 pascals (- 0.100” to – 0.200”). Thirty charcoal test kits were spread around the basement and first floor. The basement detectors read between 9.8 and 11.6 pCi/l. I was contacted about flux testing the slab and foundation wall. Radon flux coming through or out of concrete is best measured with a small CRM and a 3- or 5-liter stainless steel mixing bowl. The Radon Eye (or newer Eco-Tracker) works well for this test because of its small size and high sensitivity to changing radon levels, although it requires an external charger unless a small battery is used. The Where is the Radon Coming From? Bill Brodhead, President of WPB Enterprises, Inc. FIGURE 1