Making Sure Your Home is Radon Safe: A New Tool

A hazard, though little heard of

There is a health hazard in as many as 1 in 10 U.S. homes that is poorly understood. Radon. If you do not specifically test for it, you will never know it is there!

Radon is a gas that results from the radioactive decay of trace elements commonly found within rocky soils. Principle among these is naturally occurring trace uranium, which, over billions of years slowly decays through a sequence of different chemical elements, one of which is radon. The radioactive decay of radon, however, is rapid, which is why it is hazardous.

Radon decay, and the further decay of daughter elements over a lengthy pathway to eventual stability, produces fast moving negatively charged electrons (called beta particles) and fast moving positively charged helium nuclei (called alpha particles). Both are of high enough energy to break chemical bonds and cause genetic damage in living tissue. Being a gas, when radon is inhaled, its decay can cause damage within lung tissue. With long-term exposure, this can increase a person’s chances of getting lung cancer.

In the U.S., some 228,000 people are diagnosed with lung cancer every year. [Ref. 1] Smoking, of course, is the leading cause. However, radon also takes its toll. The U.S. Environmental Protection Agency (EPA) estimates radon is the cause of 21,000 deaths in the U.S. every year. [Ref. 2]

Some portion of this ongoing tragedy is preventable. Smoking is a choice. It is also a choice whether or not to investigate your home for hazardous levels of radon and then take well-known and effective mitigation steps, some of which are not even very costly.

The greatest determinant of whether your home may have a radon issue is where it is situated. The underlying geology is the single most critical factor. The EPA has published maps of the U.S. showing the location of the rocky soils from which radon is emitted. [Ref. 3] Outdoors, such emissions are of no concern due to the immediate dilution of radon into the vast volume of the atmosphere. Indoors, however, the air within your home turns over slowly. Modern homes are now more tightly constructed for energy efficiency, exasperating the problem. Radon gas can seep in from soil through cracks in slabs and foundations, inadequate sealing around sumps, and to a lesser extent from well water. Depending upon the season, indoor warmer air being at a lower pressure than its surroundings, a home may exhibit a “chimney effect,” actively drawing in radon. Seasonal water table variation is also a factor.

The EPA has recommended mitigation actions definitely be taken when radon, as measured by its radioactive decay, exceeds 4 pico-Curies per hour per liter of air (4 pCi/hr/l). Consideration of mitigation actions is recommended at 2 pCi/hr/l. Some 34 states have also put in place various regulations. These mainly relate to testing upon the pending sale of real estate (and civil and criminal penalties for non-disclosure) and mandatory testing in schools and certain civic buildings. The EPA has compiled a convenient guide to state-by-state resources on radon. [Ref. 3]

Detection methods

There are numerous methods by which a consumer may test for radon without the aid of a professional home inspector or radon mitigation contractor. Each has advantages and disadvantages. The first choice is between so-called “passive” and “active” approaches.

Passive approaches employ materials that may be set in homes for weeks or months and then packed up and sent away for laboratory analysis. Examples are plastic films that can be developed to show tracks left by alpha and beta particles and activated carbon pouches that can trap the particulate daughter products of radon from circulating air. There are also electret devices where an otherwise permanent charge placed on a plastic is gradually lost through contact with the high-energy emissions of radioactive decay.

At $10-30 per test kit, passive methods are inexpensive. However, if used as recommended (generally to be put in place for 5 to 90 days), variations due to location within the home and seasonality make not be captured without a well-planned multi-sample approach costing as much as simply acquiring a portable “active” device. Supporting this, in 2019, the University of Calgary published a study of radon levels in 11,727 residential buildings [Ref. 4], a conclusion of which is “…short term radon tests display a 96-99% imprecision (i.e. failure) in predicting radon levels between seasonal extremes.”

The University of Calgary study also concluded, “…across a broad North American region… newer homes [are now] containing greater and greater radon…” This is likely due to new energy efficient construction being more air-tight, less ventilation due to the use of air conditioning, and the larger footprint of newer, mostly single story, homes.

Active approaches are defined as those employing powered devices to detect radioactive decay. There are several such technologies, but only two are available as products a consumer can purchase at a reasonable price. These use either semiconductor detectors or ion chamber detectors. The semiconductor-based approaches do not have the sensitivity of the ion chamber approach that is the subject of this article. Thus, they are slower to develop stable and accurate data. Moreover, clear distinctions between consumer-oriented products can be made on the basis of the convenience of well-designed smartphone-based set-up and information display software.

The RadonEye RD200 from Ecosense          

Ecosense, Inc., based in Silicon Valley, was formed in July of 2019 to professionally introduce the novel ion chamber approach to radon measurement pioneered by FTLab of Korea to the North American market. FTLab’s consumer product, the RadonEye RD200, has been well received throughout its test marketing on Amazon. Between North America and Korea nearly 40,000 of these devices have been sold. New however, Ecosense is has now begun to more actively promote both this consumer product and the newly introduced RadonEye Pro 200P, a WiFi-equipped device which has been designed especially for fleet use by the professional home inspectors and radon mitigators enabling the simultaneous reporting of the inspection of multiple properties.

Significantly, the RadonEye RD200 and the RadonEye Pro 200P share the same radon detection technology, a pulsed ion chamber read by super-sensitive U.S.-patented analog measurement electronics capable of 30 counts per hour per pico-Curie per liter count rate. The approach used is very fast, updating readings every 10 minutes and achieving +/- 10% of the final average value within one hour of set-up. The technology is very accurate and in academic studies has compared favorably to the RAD7 by Durridge Inc., a benchmark professional monitor priced at several thousand dollars. [Ref. 5] Ecosense has introduced the RadonEye RD200 consumer product at $179.

The RadonEye RD200 is easily set up using Bluetooth communications to your smartphone. Either an Android or iOS smartphone is fine. The appropriate RadonEye app may be downloaded from Google Play or the Apple App Store. Once synched, the RadonEye RD200 is best first used as a “sniffer.” Because the device is so fast, the unit may be moved around a home every 30 to 40 minutes to find areas with high radon levels. The built-in OLED display displays the last measurement taken and scrolls through averages determined over longer periods of time. The data may also be accessed through the RadonEye app, which synchs the RadonEye RD200’s locally stored data to your phone and constructs graphic displays of radon levels over time. Once the most meaningful area of your home is identified, the device can be left to monitor on a continuous basis.

If your readings are high

There are several actions that may be taken if radon in your home reads high. First, it would be wise to see how readings trend over time placing the RadonEye RD200 in different locations. Opening windows more often on hot days may be helpful. If readings are consistently high, you may wish to explore means of sealing cracks in your slab or foundation should they be accessible. Similarly, are through-holes for sumps or piping well sealed? In the case of consistently elevated readings it may be wise to bring in a radon mitigation professional, who may recommend installing a 24-hour fan to duct basement or crawl space air above your roofline. The beauty of having a continuous measurement device like the RadonEye RD200 is that a sequence of steps may be explored prior to determining whether increasing levels of expenditure are necessary. Whatever they are, avoiding the chances of serious health issues may be well worth it.


With the RadonEye RD200, you can keep a close eye on radon levels in your home and monitor for seasonal changes. The minimum outcome is the peace of mind that comes with knowing your home is safe. If it is, great! Lend the device to friends and neighbors or donate it to a school for science classes. If you find issues, work the problem step-by-step. Should sealing or active ventilation appear necessary, Ecosense can recommend trusted radon mitigation professionals to help you lower the radon levels within your home to within safety guidelines. We stand by to become your partner in your quest to insure you and your family breathe the healthiest possible indoor air.

Peter C. Foller, Ph.D.


  4. F.K.T. Stanley, et al., Scientific Reports, 9, Article number 18472 (2019)
  5. “Intercomparison of Commercially Available Active Radon Measurement Devices in a “Discovered” Radon Chamber,” Marco Carmona, et al, Radiological Health Engineering Laboratory Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Consortium for Verification Technology under the Department of Energy National Nuclear Security Administration, award number DE-NA0002534.