Best Radon Detector for Home: Continuous Monitors Compared

The EPA recommends fixing your home if radon is 4 pCi/L or higher and considering a fix between 2 and 4 pCi/L. For comparison, the EPA puts the average indoor level at about 1.3 pCi/L and outdoor air at about 0.4 pCi/L. There is no known safe level, so lower is better.

Consumer continuous monitors track trends well once they have run for several days, but short readings swing a lot because radon itself changes by the hour. Judge your home by the multi-day or long-term average, not a single hourly number. For a home sale, buyers usually require a test by a certified professional or an accredited lab kit.

The EPA says a short-term test runs 2 to 90 days and a long-term test runs more than 90 days. Run any detector at least 48 hours before trusting the result. A long-term average is the best picture of your year-round exposure because radon is often higher in winter when the house is closed up.

Put it on the lowest lived-in level of the home, such as a finished basement or first-floor bedroom. The EPA advises placing it at least 20 inches above the floor, away from drafts, exterior walls, high heat and humidity, and out of kitchens and bathrooms.

The EPA estimates that nearly 1 in 15 US homes has radon at or above the 4 pCi/L action level. Radon is the leading cause of lung cancer among nonsmokers and is linked to about 21,000 lung cancer deaths a year in the US, according to the EPA.

The EPA's consumer guide puts the cost of having a contractor fix a home at about $800 to $2,500, similar to other common home repairs. Most systems use a fan that runs all the time; a fan drawing 60 W uses about 526 kWh a year, roughly $89 at 17 cents per kWh.

A kit gives one result for one period and is mailed to a lab, while a continuous detector keeps measuring for years with no lab fees. A detector is worth it if you want to watch seasonal changes, check a mitigation system, or test several rooms. A one-time kit is enough for a single check.

Only if you want alerts away from home. The Ecosense EcoQube EQ100 has built-in 2.4 GHz Wi-Fi, while the Airthings Wave Radon and Corentium Home 2 use Bluetooth and need an Airthings Hub for 24/7 remote data. The Ecosense RD200 uses Bluetooth and its own screen.

No. Radon is a gas, so HEPA filters do not remove it and a dehumidifier does not change it. The standard fix is active soil depressurization, a pipe and fan that pull radon from under the slab and vent it above the roof.

Ecosense lists a first reading 10 minutes after the RD200 or EQ100 is powered on. Airthings detectors build their short-term and long-term averages over days and months. Whichever you use, wait at least 48 hours before acting on a number, and use the long-term average for decisions.