Question 1

What happens when radon decays?

Accepted Answer

When radon decays, it “explodes” into two smaller atoms, or “decay products”, one of which is radioactive, plus several very high energy particles.  Because radon gas does not interact with any known substances or objects, including any form of detection equipment, it is not possible to measure radon gas directly. Therefore, it is this smaller, radioactive decay product and the very high energy particles that are used to measure the presence of radon gas.

Question 2

Does radon make my home radioactive?

Accepted Answer

No. Radon, and the products it decays into, do not attach themselves to the home building materials or furnishings, and these items will pose no radiation risks to the occupants of the home.

Question 3

Will radon gas continue to build up as my home is closed?

Accepted Answer

No.  If a homeowner opens all the doors and windows to bring fresh air into the home, the radon level will decrease.  Within roughly 12 hours of closing the doors and windows, the radon level will have risen to its average, normal level in the home.  At that point, the number of radon atoms entering the house will equal the number of radon atoms that are decaying away at that time, and this “radioactive equilibrium” maintains the radon level at a fairly constant level in the home over time.  The radon level will not continue to build up to higher and higher levels.  Vacant homes are not at risk of obtaining a "false positive" simply because there has not been activity in a home for several months.

Question 4

Are charcoal canisters as accurate and reliable as continuous radon monitors (CRMs)?  Are all CRMs equally reliable and accurate?

Accepted Answer

Any radon test, properly conducted, will yield valid test results. The major difference between the two is that an activated charcoal test only gives one reading, the average radon level during the entire test period, while a CRM test provides hourly readings of the radon level during the test period. Activated charcoal tests can be performed by home inspectors, realtors, and home owners, while a CRM test usually requires a radon professional to conduct the test.
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Activated charcoal tests are sensitive to moisture and humidity in the air, cooking smells, and other household odors, and it is possible to alter the effectiveness of these test kits if they are exposed to these conditions. Furthermore, if the radon level during the last 12-24 hours is significantly higher or lower than the average radon level earlier in the test, activated charcoal kits can be influenced (biased) by this change at the end of the test and yield a false reading.  Finally, there is no way of detecting any changes to the test environment with an activated charcoal kit.
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CRM tests, on the other hand, are not sensitive to moisture and odors, and are not biased towards the last 12-24 hours of the test period. They have the capability to record not only the radon level on an hourly basis, but also relative humidity, room temperature, and barometric pressure, thus making any changes in the test environment more obvious. Normal hourly variations in radon levels can be seen in the graph accompanying the radon report.  While CRMs are tamper evident, they are not tamper proof.
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It is also important to note that not all CRMs are equivalent.  Expensive models, like the FemtoTech 510LP model we use, are much more sensitive and can gather more data than less expensive CRMs.  This increased sensitivity and precision can allow them to be more accurate and reliable than less expensive models, some of which are prone to yield false positive and/or false negative readings.

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Frequently asked questions

What happens when radon decays?

Does radon make my home radioactive?

Will radon gas continue to build up as my home is closed?

Are charcoal canisters as accurate and reliable as continuous radon monitors (CRMs)? Are all CRMs equally reliable and accurate?