When conducting a measurement be sure to consider the following mechanicals are in the correct state.
Examples of factors that could cause radon to spike:
Changes to the structure and mechanicals can also have a significant impact on the measurement. In figure 6 roofing contractors came at hour 48 and tore off and replaced the shingles and roofing paper on back half of the roof. At hour 72 the roofing contractors returned to replace the soffits, fascia and attic baffle vents. Some might argue that in this case a 96 hour test was to the seller’s demise.
However, we did retest and the overall results indicated very low results, shown in figure 7. Also, consider this: What if this was a 48-hour test conducted only on day 3 & 4. Those ‘spikes’ could be misconstrued for a consistent diurnal cycle or the natural stack effect of the home if gas forced-air furnace is used in the winter.