Should I place a radon test in the basement or main floor?

Place the test in the lowest level of your home that is regularly occupied or could be regularly occupied. If you use your basement as a living space, family room, or bedroom, test there. If the basement is unfinished and you never spend time there, test on the main floor. For real estate transactions, testing typically occurs in the lowest livable level regardless of current use.

How high should a radon detector be off the floor?

Place the radon detector 20 inches to 6 feet above the floor, in the breathing zone. A table, shelf, or nightstand at normal furniture height is ideal. Avoid placing it directly on the floor, as floor-level readings may not represent the air you actually breathe. Also avoid placing it above 6 feet where air patterns differ.

Can I place a radon test in a bathroom or kitchen?

No. Bathrooms and kitchens should be avoided because high humidity, exhaust fans, and water use can interfere with test results. Moisture can affect charcoal-based test kits, and exhaust fans create air currents that disrupt accurate measurement. Choose a bedroom, living room, or family room instead.

Does radon detector placement affect results?

Yes, significantly. Placing a detector near a window, door, or vent can produce falsely low readings due to air dilution. Placing it in an enclosed closet or near a sump pit can produce falsely high readings. Proper placement in the breathing zone of a regularly occupied room, away from drafts and moisture, is essential for accurate results.

How many radon tests do I need for my home?

For most single-family homes, one test in the lowest livable level is sufficient for an initial screening. Larger homes, homes with multiple foundation types, or multi-story homes may benefit from tests on multiple levels. If your initial test shows elevated levels, a follow-up test or professional testing can confirm the results.

Where to Place a Radon Detector

A radon test is only as good as its placement. Put the detector in the wrong spot, and you could get a reading that does not reflect what your family actually breathes. This guide covers the EPA's placement guidelines with practical, room-by-room advice.

1. General Placement Rules

Lowest livable level: Test in the lowest floor of your home that is used or could be used as living space.
Breathing zone: Place the device 20 inches to 6 feet above the floor. This represents the air you actually breathe.
Away from drafts: Keep it at least 3 feet from windows, doors, and exterior walls. Air infiltration near these areas dilutes radon readings.
Away from moisture: Keep the detector away from kitchens, bathrooms, laundry rooms, and any area with high humidity or standing water.
Undisturbed location: Choose a spot where the detector will not be moved, bumped, or covered during the test period. Find answers to common radon questions on our FAQ page.

2. Best Rooms for Testing

Ideal Locations

Basement family room or rec room
Basement bedroom
Ground-floor living room
Ground-floor bedroom
Home office on lowest level

Avoid These Rooms

Kitchens (moisture, exhaust fans)
Bathrooms (humidity, ventilation)
Laundry rooms (moisture, dryer exhaust)
Closets (restricted air flow)
Utility rooms (near furnace or water heater)

3. Height and Position

The ideal height for a radon detector is in the breathing zone, which is 20 inches to 6 feet above the floor. A nightstand, end table, or bookshelf works well. Place it at least 3 feet from any exterior wall, 1 foot from any interior wall, and away from heating or cooling vents.

Quick Placement Checklist

20 inches to 6 feet off the floor
At least 3 feet from exterior walls
At least 1 foot from interior walls
At least 10 feet from any exterior door or window
Away from HVAC supply and return vents
On a stable surface where it will not be disturbed

4. Locations to Avoid

Certain locations will produce inaccurate results and should be avoided.

Near sump pits: Open sump pits concentrate radon. Placing a detector nearby will overestimate room-level exposure.
In direct sunlight: Heat from sunlight can affect charcoal-based test kits and electronic monitors.
Near ceiling fans: Air circulation from fans disrupts the air sampling pattern around the detector.
On the floor: Floor-level readings do not represent the air you breathe at standing or sitting height.

5. Testing Multi-Level Homes

For homes with multiple levels, start with the lowest livable level. If that test shows elevated radon, you may want to test upper levels to understand how radon distributes through your home. Each level will typically show lower readings than the one below it. For a comparison of all available testing devices, see our radon test kit types comparison.

6. Closed-House Conditions

For accurate short-term test results, maintain closed-house conditions starting 12 hours before the test begins and continuing throughout the test period.

Closed-House Requirements

Keep all windows and exterior doors closed
Operate HVAC as normal (heating and cooling is fine)
Avoid operating whole-house fans or attic fans
Normal entry and exit through doors is acceptable

7. Common Placement Mistakes

Testing Only the Upper Floor

If your home has a basement or ground level, testing only on the second floor will underestimate radon exposure in the lowest lived-in areas.

Placing Near an Open Window

Even slightly open windows bring in outdoor air that dilutes radon readings, producing falsely low results.

Moving the Detector

Once placed, the detector should remain undisturbed for the entire test period. Moving it can disrupt the measurement and void the results.

Getting placement right is important because radon is a serious lung cancer risk. Accurate test results help you make informed decisions about protecting your family.

Frequently Asked Questions

Get Accurate Results with Professional Testing

Our professionals know exactly where and how to place monitors for the most accurate results. Learn about our testing services.

Schedule Professional Testing

Where to Place a Radon Detector: Room-by-Room Placement Guide