How to Prepare Your Home for a Radon Test

A radon test is only as accurate as the conditions it runs under. Unlike most home inspections, where you can go about your day while someone works, radon testing asks something of you: your house needs to behave a certain way for the duration of the test.

The requirements are not complicated, but they are easy to accidentally violate. Here is exactly what to do before and during a test so the number you get is a real reflection of your home.

Closed-House Conditions, Explained

The single most important requirement is what the industry calls closed-house conditions. Radon accumulates indoors. If a house is being actively ventilated during a test, the measured concentration drops — not because the home has less radon, but because you are temporarily flushing it out.

Closed-house conditions mean:

• Windows stay closed on all levels of the home.
• Exterior doors stay closed except for normal entry and exit — walking in and out is fine, propping the door open while you unload groceries for twenty minutes is not.
• Window air conditioners and whole-house fans stay off.
• Fireplace dampers stay closed unless the fireplace is in use.
• Attic and crawl space vents that you can control stay in their normal position.

Critically, closed-house conditions must begin 12 hours before the test starts, not when the device is placed. If a tester arrives at 9 a.m. Monday, your windows should have been closed since roughly 9 p.m. Sunday. This pre-conditioning period lets the home reach the equilibrium the test is meant to measure.

For a standard 48-hour short-term test, that means about 60 hours of keeping the house closed up.

What You Can Still Run Normally

Closed-house conditions cause more anxiety than they should. Plenty of normal life continues:

• Your furnace and central air run normally. These recirculate indoor air rather than bringing in outside air, so they do not compromise the test. In a Syracuse winter, nobody expects you to turn off the heat.
• Bathroom and kitchen exhaust fans can be used for their normal short duration. Running a bath fan for ten minutes after a shower is fine; leaving it running for eight hours is not.
• The clothes dryer is fine with normal use.
• Coming and going is fine. Doors opening and closing in the ordinary course of a day will not ruin a test.
• Ceiling fans are fine — they move indoor air rather than exchanging it.

Where the Device Goes and Why

Testing happens in the lowest livable level of the home. That phrase does specific work, and it is worth understanding.

Radon enters from the soil, so concentrations are highest at the lowest point of the structure and decrease as you move up. “Livable” means space that is or reasonably could be occupied. A finished basement family room is clearly livable. An unfinished basement is generally treated as livable for testing purposes, because it could be finished and because people use basements for laundry, storage, and hobbies.

Placement within that level follows protocol as well. The device should be positioned:

• Roughly 20 inches to 6 feet above the floor, in the breathing zone.
• At least 3 feet from exterior doors and windows.
• At least 1 foot from exterior walls.
• Away from direct sunlight, heat sources, and drafts.
• Away from areas of high humidity, which can affect certain devices.

It should not go in a closet, a crawl space, a kitchen, or a bathroom. These locations produce readings that do not represent the air people actually breathe.

Do Not Move or Disturb the Device

Once placed, leave it alone. Do not relocate it, cover it, unplug it, or open windows near it. Continuous radon monitors log hourly readings and many detect movement or power interruption, which means tampering shows up in the data and can invalidate the test.

If you have curious children or pets, mention it when scheduling so the device can be positioned somewhere out of reach while still meeting placement requirements.

Timing Considerations in Central New York

A few local factors are worth planning around.

Severe weather. Testing during high winds or rapidly shifting barometric pressure can produce readings that are not representative. Storms change the pressure relationship between soil and house, which affects how much soil gas gets drawn indoors. If a major system is moving through Central New York, rescheduling by a day or two is reasonable.

Season. Radon levels in this region typically run higher in winter, when homes are sealed tight and the stack effect is strongest. A summer test with windows that have been closed only 12 hours may read lower than the same home would in January. This does not invalidate summer testing, but it is context for interpreting a result near the action level.

Real estate timelines. If testing is part of a transaction, build in the full window. A 48-hour test plus 12 hours of pre-conditioning plus scheduling means you want several days of margin before your inspection contingency expires, not hours.

A Simple Checklist

The night before: close all windows on every level. Turn off window AC units and whole-house fans. Close the fireplace damper. Let the house sit closed overnight.

Test day: keep windows closed. Use exterior doors normally but do not prop them open. Let the tester place the device where protocol requires rather than where seems convenient.

During the test: do not touch the device. Keep windows closed. Run heat or AC as usual. Use exhaust fans only briefly.

If something goes wrong — a window got left open, a contractor propped the door, the power went out — say so. A tester would far rather rerun a test than hand you a number that does not mean anything.

Why Getting This Right Matters

An inaccurate radon test is worse than no test, because it produces false confidence. A home that reads 3.2 pCi/L because a basement window was open all weekend might genuinely be at 6 pCi/L — and the homeowner now believes they are fine and will not retest for years.

Onondaga County is EPA Radon Zone 1, the highest-risk designation. Elevated readings here are common enough that an accurate measurement is worth the minor inconvenience of a closed-up house for a couple of days.

If your result comes back above 4.0 pCi/L, a mitigation system is a permanent fix, typically installed in a single day. And if it comes back low, you have a documented number and genuine peace of mind.

Ready to schedule certified radon testing in the Syracuse area? Call (315) 234-2853 and we will walk you through exactly what to do before test day.

Preparation matters most for closed-house testing in Manlius and Camillus, where basement use patterns vary widely from home to home.