Real-Estate Test Invalidated by Open Window and Poor Placement
On a tight real-estate deadline, you place a continuous radon monitor (CRM) in the finished basement family room of a 1970s ranch. The CRM sits on a bookshelf 5 ft above the floor, 8 in from the exterior wall and 2 ft from a sliding window. You instruct the seller to maintain closed-house conditions for 12 h before and during the 48-h test. At hour 30 the seller opens the window for 45 min to clear paint fumes and leaves the basement door open to the upstairs hallway, where another window is open. The CRM logs an 8.1 pCi/L average and an 11.2 pCi/L peak; the tamper flag is not triggered. The buyer's agent asks whether the 8.1 pCi/L can be used to demand mitigation before closing. You have the hourly data and a signed closed-house checklist.
1. Is the 8.1 pCi/L result valid for a real-estate decision under closed-house and placement requirements? Explain your reasoning.
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No. The result has two independent protocol failures. First, placement is wrong: the CRM is only 8 in from an exterior wall and 2 ft from a window, while it should be at least 3 ft from exterior walls and 3 ft from windows and other openings. A height of 5 ft is acceptable because devices should be roughly 20 in to 6 ft above the floor. Second, closed-house conditions were broken: a window was open for 45 min at hour 30 and an upstairs window was open with the basement door open. Closed-house conditions must exist for 12 h before and throughout the test, with normal HVAC operation and only momentary entry/exit. The absence of a tamper flag does not cure either defect. The 8.1 pCi/L average is not representative and must not be used to negotiate or size mitigation.
2. What should you do before and after restarting the test?
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Invalidate the current test in writing and do not average it with any follow-up data. Explain the specific deviations to the buyer and seller. Then restore closed-house conditions for at least 12 h before restarting. Relocate the CRM to an interior location: 20 in to 6 ft above the floor, at least 3 ft from exterior walls, windows, and doors, at least 4 in from other objects, and away from sumps, drains, and HVAC returns. Run a new 48-h test and keep the hourly data. Because a real-estate deadline is involved, schedule the restart immediately and tell the agents that the prior result cannot be salvaged. If the client wants a result before closing, the only defensible option is a compliant new test, not a shortened or adjusted version of the invalid one.
3. How should the invalid result be documented and communicated?
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Document it as an invalid test caused by protocol deviation, not as a low or high radon result. Record the placement measurements, the time and duration of window opening, the open basement door, the checklist signature, and the hourly data. The report should state that no conclusion about radon concentration or mitigation need can be drawn. Do not include the 8.1 pCi/L in a table of valid results and do not average it with the restart. Communicate in writing to both agents and the client, with a clear restart date and the conditions required. If the closing cannot wait, the honest recommendation is to proceed without a radon contingency or delay, not to rely on an invalid number.