Help us get an accurate radon reading.
The buyer has asked for a radon test as part of the home inspection. The test runs for 48 hours, and a few simple conditions need to be in place before and during it. Following the steps below keeps the result valid under the ANSI/AARST measurement protocol — which Colorado state law requires licensed radon professionals to follow.
What you need to do
Close the house 12 hours before the test starts
All exterior windows on every level must be closed for at least 12 hours before I arrive to start the test. Exterior doors stay closed too, except for normal entry and exit. This is the single most important step — the test is invalid without it.
Keep the house closed for the full 48 hours
Once the test starts, exterior windows stay shut and exterior doors are only opened briefly to come and go. Interior doors can be used normally. Live in the home as you typically would otherwise — eat, sleep, watch TV, all of it.
Don't move, cover, or unplug the monitor
The continuous radon monitor needs to stay exactly where I place it for the full 48 hours. Don't move it, cover it, set anything on top of it, or unplug it. The screen will go to sleep — that's normal. The test is still running in the background.
Run heating and cooling normally
Set the thermostat to a normal occupied temperature (roughly 65–80°F). Forced-air furnace, heat pump, mini-split, baseboard, wall, and ceiling heat are all fine. If the home has a permanent radon mitigation system, leave it running.
Turn off anything that ventilates with outside air
Whole-house fans, window fans, attic fans, and standalone humidifiers or dehumidifiers that exchange air with the outside should be off for the duration. Permanently installed ERV/HRV systems may continue normal operation.
That's it — I'll come back to pick up the device
The buyer's agent will coordinate a pickup time once the test has run its full course. That's usually right around 48 hours, but sometimes it's a bit longer depending on schedules. If anything unusual happens during the test — a window left open, a power outage — please text or call me so I can note it.
Quick reference
You can
- Open and close exterior doors briefly to come and go
- Use the heating or cooling system as you normally would
- Open and close interior doors freely
- Cook, shower, do laundry, and live in the home normally
- Run a permanent radon mitigation system (in fact, please do)
- Run a permanently installed ERV/HRV system
Please don't
- Open exterior windows during the 12 hours before or the 48-hour test
- Leave exterior doors propped open
- Move, cover, or unplug the radon monitor
- Run whole-house fans, window fans, or attic fans
- Burn a fireplace or wood stove if it pulls combustion air from outside
- Schedule fireplace use, parties, or unusual activity during the test
Common questions
Is radon dangerous? Should I be worried?
Radon is a naturally occurring, odorless gas that comes up out of the soil. Many homes across Colorado test above the level where mitigation is recommended, and a working mitigation system reduces it effectively. A high test result is a fixable issue, not a deal-breaker.
Where in the house will the monitor go?
In the lowest level of the home that could be occupied. For a real-estate test that usually means a basement — finished, partially finished, or even unfinished if it could reasonably be used as a work area, playroom, or bedroom someday. If there's no basement, the test goes on the lowest floor with living space. The monitor sits at least 20 inches off the floor, away from drafts, exterior walls, and direct sunlight, and not in a closet, kitchen, bathroom, or laundry room.
The screen on the monitor turned off — is it still working?
Yes. The LED display goes to sleep after a few minutes to save power, but the monitor is still running and recording data the whole time. Please don't tap, wake, or otherwise mess with it to check — just leave it alone and let it do its job.
Can I still use my fireplace or wood stove?
It's best not to during the test. Fireplaces and wood stoves that draw combustion air from inside the house can change the pressure dynamics enough to affect the reading. If you have a sealed direct-vent unit, it's generally fine — but if you're unsure, please ask before lighting it.
What if the weather changes — storms, wind, temperature swings?
Continuous radon monitors are designed to handle normal weather variation, and the 48-hour test is meant to average out short-term fluctuation. You don't need to do anything differently. If there's a major event (an extended power outage, for example), give me a heads-up.
What happens if the result comes back high?
I'll report the result to the buyer's agent along with the full continuous data log. From there, the buyer and seller typically negotiate mitigation as part of the transaction. A radon mitigation system is a relatively standard fix, usually installed in a day by a licensed contractor.
Questions during the test?
Text or call anytime — I'm happy to help with anything that comes up during the test.
Thank you for helping us get this right. — Jeff Sand, Straight Edge Home Inspections
