How to Read a Radon Detector

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Radon is an odorless, tasteless and invisible gas typically found in basements or areas of a home that are beneath the ground. Radon is also the No. 1 cause of lung cancer in nonsmokers in the United States, according to the Centers for Disease Control and Prevention. Meters typically range in cost from $20 to $150 depending on the type of test being done. Charcoal tests are cheapest and typically take 48 to 96 hours to test the air. But digital kits, which require an electrical source, are more expensive but give a reading almost immediately.


Step 1

Purchase a test kit, either charcoal-based or digital, from a local hardware store. The digital monitor can be left plugged in to regularly monitor the air for radon, which can increase over time in an area.

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Step 2

Prepare the area for testing. All windows and doors should have been closed for at least 24 hours before testing.


The canister that comes with the charcoal kit or the digital monitor should be placed 2 feet above the floor, 1 foot away from all exterior walls, 4 inches away from any other objects in the room and at least 3 feet away from any windows, doors or other openings. Also, do not place the canister in a cupboard or box. The canister should be exposed to the air that is being breathed by all occupants of the home.


Step 3

Do not move the test canister or digital reader while the test is being conducted. A digital reader can be read after approximately 90 seconds.

Step 4

Read the results. In a charcoal test, the canisters are typically sent off to a lab. You will need to carefully close the canister and then place it in the pouch that it came with. Then, follow the shipment instructions. The results are usually available within 48 hours after the test facility receives the canister. Results are typically mailed or sent via email in some cases. You can also call the lab company to retrieve your results.


On a digital reader, the radon reading will be between 0.1 to 999.9 picocuries per liter, or pCi/L. Any reading over 4.0 pCi/L is considered dangerous, and an alarm will typically sound on the reader.

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