AARST_Radon_Reporter_Q42025

THE RADON REPORTER | 7 MITIGATION Basement Garage T2 T1 T3 T5 T4 S1 Green Line: Pressure Differential at T2 EXAMPLE 1 Weakest test point T2 = -5Pa When I Was on Site Simple house, right? We had good PFE. We should be good to go, right? Unfortunately, we were not good to go. Radon concentrations were still elevated. For clarity, T4 and T5 are in a main floor garage, and we did have great PFE up there from the suction point in the basement. We could have put a second suction point at T2, since that was the weak point. However, there appeared to be enough pressure differential between the basement and sub-slab that a second suction point there would not have helped. So, we measured the pressures over time. The next image is the pressure vs time graphed. The green line represents the pressure differential between the sub-slab and the basement at T2. It goes above the zero line a significant amount of time and goes as high as 8 Pa positive. It also spends some time below zero, where we want it to be. When I had measured this pressure differential previously it was when the pressure differential was below the zero line. We measured radon concentrations while we were taking these pressure differential measurements. As expected, radon concentrations were elevated when the pressure differential was above the zero line. A second suction point was added near T2 and the problem was solved. This is the only time we have needed to overcome this much baseline pressure differential, so it did not make sense to us to add another pipe run to this basement without knowing it was needed.