Protocol
ANSI/AARST closed-building conditions for multifamily radon tests
August 26, 2026
What are closed-building conditions on a multifamily radon test?
Closed-building means the property is run like occupied housing during the test window: windows closed, exterior doors not propped, and HVAC in its normal setting. The goal is a measurement that reflects how the building is actually lived in, not a week of airing units out. ANSI/AARST multifamily guidance treats those conditions as part of a valid test, not a footnote.
NOI Radon confirms protocol with your quote so the scope matches the lender or program. Devices are placed and retrieved to that guidance, with closed-building conditions accounted for during the test window.
How long do closed-building conditions need to hold?
Typical short-term measurements ask for closed-building roughly twelve hours before devices start and then for the full test window. Exact timing is confirmed with the protocol for that job. The operational point for property managers is simple: do not open windows to "freshen" units the night before, and tell residents the same.
If a unit cannot stay closed because of a repair or a vacancy turnover, say that before placement. Moving a device after the fact is worse than planning around the unit.
What does ANSI/AARST change compared with a casual placement?
Placement locations, device count, and quality controls are specified. You do not drop a kit in a lobby and call the building tested. Ground-contact units, unique foundations, and representative sampling all matter. Retrieval has to hit the same protocol clock as placement. That is why nationwide scheduling still has to respect the window, not just the travel day.
The current ANSI/AARST multifamily measurement standard (MAMF) is the usual citation reviewers expect to see named, alongside any program overlay from FHA MAP or an Agency lender.
What should site staff tell residents?
Give clear notice: devices will be in designated units for a short window, windows stay closed, and staff will place and retrieve without a long disruption. Residents do not need a physics lecture. They need the dates and the closed-window rule. NOI Radon coordinates that notice with on-site staff so the test week stays quiet.
How do closed-building conditions show up in the report?
The report should state that conditions were required, how they were communicated, and any units that broke the rule. A lender-ready write-up is honest about exceptions. Hiding an open-window unit helps nobody when a reviewer asks.
| Closed-building check | Why it is in the plan |
|---|---|
| Windows and exterior doors closed | Keeps outdoor air from washing out the measurement |
| HVAC in normal occupied operation | Matches how the building actually runs |
| Notice to residents and staff | Prevents helpful airing-out the night before |
| Exceptions logged | Gives reviewers a defensible file |
| Retrieval on the protocol clock | Protects the test window you already paid for |
Protocol questions on a live deal belong in the quote form, with the program and deadline attached.