The Open Sliding Door and the Four-Day Deadline
A two-story 1978 colonial with a finished basement goes under contract, and the buyer's agent orders a 48-hour short-term test using two activated charcoal devices. On arrival for placement, the tester finds the basement sliding door open to the yard, a window air conditioner running in the first-floor family room, and the homeowner's dehumidifier set to continuous drain. The tester notes the conditions, places one device in the basement laundry room on a shelf 5 feet above the floor and one in a first-floor bedroom, and returns 48 hours later. Readings are 3.9 pCi/L in the basement and 2.2 pCi/L on the first floor. The seller insists the house was closed up the whole time. The tester's own report template has a checkbox for closed-house conditions confirmed, and the tester had already checked it based on the seller's assurance before noticing the door. The buyer demands a mitigation quote before the inspection contingency expires in four days.
1. Is this a valid short-term test under closed-house protocol? Identify specifically what passes and what fails.
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The test fails on conditions, not on the device or the duration.
Conditions - fail. Closed-house protocol requires all exterior windows and doors closed for at least 12 hours before deployment and for the entire test period. A basement sliding door standing open to the yard breaks that, and the effect on the basement number cannot be corrected after the fact. The window air conditioner is a second problem if it draws outside air: window units introduce outdoor air and change room pressure, so they should not be running during a test. The continuously draining dehumidifier is generally acceptable but should be documented.
The pre-checked checkbox is the worst part. A report that asserts conditions that were not true is a misrepresentation, not a clerical slip.
Placement - pass. A basement laundry room on the lowest livable level, on a shelf 5 feet up, sits in the breathing zone and is not against an exterior wall. That is close to what EPA and AARST placement guidance asks for.
Duration - pass. 48 hours meets the minimum for a real estate short-term test.
Verdict: conditions fail, everything else passes, and the report cannot be delivered as a completed closed-house test.
2. How should the 3.9 pCi/L basement result be reported and interpreted against the 4.0 pCi/L action level?
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3.9 is not a pass. The action level is 4 pCi/L, but charcoal devices carry a precision on the order of ±25% at that level, so 3.9 and 4.3 are the same number within measurement uncertainty. A single canister cannot distinguish 3.9 from 4.1, and it certainly cannot certify a house as clear.
The result also lands in the 2–4 pCi/L band, which EPA describes as "consider mitigation," not "no action." Interpretation should say: at or near the action level, retest and consider mitigation, rather than clearing the property.
The 2.2 pCi/L upstairs does not rescue the basement number. The decision location is the lowest livable level; report each location separately and label the basement as the decision number. Do not average devices, do not average floors, and do not split the difference - all of those manufacture a lower number out of the same data.
What the report should carry: the measurement itself, the device type, the placement, the observed conditions, a statement that the closed-house requirement was not met, and a recommendation to retest under correct conditions before any mitigation decision or quote.
3. The buyer wants a mitigation quote within four days. What do you tell the buyer's agent, and what goes in writing?
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Tell the agent plainly that a calendar does not change measurement physics. A mitigation price quoted off an invalid test is a guess that can be wrong in either direction - the buyer might pay for a system the house does not need, or clear a house that reads 6 pCi/L on a proper test.
Options to put in writing:
- Retest correctly. Twelve hours closed before placement plus 48 hours, one device in the basement and one on the first floor. Results in about three days, which fits inside a short extension.
- Request an extension of the inspection contingency, or draft the contract so mitigation is negotiated after a valid test.
- Long-term testing (90-day alpha-track or a long-term monitor) is more defensible but slower; it is the right answer if the clock cannot move and the parties can wait.
In the written report, document the conditions found, the deviations, the placement, and an explicit statement that the results are qualified and do not represent closed-house conditions. The tester should also correct the pre-checked box and note why.
What the tester must not do is present invalid data as a completed test to hit a deadline. The professional obligation is to the accuracy of the measurement, not to the transaction schedule.