There are two basic types of radon testing equipment: passive and electronic. While no test device is absolutely tamperproof, the passive test systems make it much easier to manipulate the test results downward. 

    To understand why, let’s first review the Environmental Protection Agency’s (EPA) protocol for the a radon test:

1. All windows must be kept closed. Exterior doors should be kept closed, except for momentary entrance and exit.
2. HVAC system should operate normally, with the thermostat set between 67º and 77º F.
3. Whole-house fans, fireplaces and wood stoves should not be operated. 
4. The test device should not be moved or otherwise tampered with.

    The premise of the test standard is to replicate the way most people live in their homes: with the windows closed and the HVAC system on. It is a “closed house test.” The occupant of the house can come and go as often as they want, as long as they do not leave a door open.

    While all houses have a small amount of air exchange between the interior and outside, even with the doors and windows closed, opening them will usually reduce the radon level somewhat. Any kind of air exhaust systems also tend to the reduce the radon concentration, although they may possibly increase it and, of course, moving the test device outside will lower the radon reading significantly. 

    Examples of passive devices would a charcoal canister or Electret Ion Chamber (EIC). They are both small, simple, and do not require any electric power to operate or have any type of environmental monitoring sensors. The only test result obtainable is the average radon level for the duration of the test. When these systems are used, the single tamper-resistant feature that can be added is securing the device in place with a special tape that shreds when moved to indicate tampering.

    Electronic monitors require power, but have a battery in case the power fails during the test. The one that we use, the Radalink AirCat, is a typical electronic monitor and has the following tamper-resistant sensors:

1. A movement sensor.
2. An air pressure sensor that keeps a continuous log of the opening of any doors or windows and the length of time they remain open. 
3. A temperature and humidity sensor that also keeps a continuous log to indicate any temperature or humidity changes.
4. An hourly radon concentration reading.

    A technician at Radalink, in Atlanta, Georgia, reviews all the sensor data, looking for any indications of changes in the test conditions that would indicate tampering, before releasing the final report to the customer. The result is a test reading that is much less likely to have been manipulated. We occasionally have a test voided by Radalink because of evidence of tampering, and the home has to be retested. It does not happen often, but it does happen.

    While the passive radon test devices are approximately as accurate as an electronic ones, we suggest using a company with an electronic system to be assured of the  most accurate result possible when radon testing for a real estate transaction. Passive devices are just fine for testing your own home or a follow-up test after a radon mitigation system has been installed.

    Also, see our blog post Will opening the windows reduce the radon level in a house? and Will the radon test come back sky-high in a house that has been empty and closed-up for months? 

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Here’s links to a collection of our blog posts about “RADON":

• Is a radon mitigation fan required to be on a dedicated circuit breaker/fuse in the electric panel?

• What happens to a radon test result if the windows were opened, the test device moved, or there was any other evidence of tampering during the test? 

• Where do I find the Florida laws regarding radon?

• Can I test vacant land for radon before building a house? 

• Is radon mitigation possible for a condominium?

• Do radon mitigation systems require maintenance?

• What is the average life expectancy of a radon mitigation system?  

• Do older houses have higher radon levels than new houses? 

• How long does it take to get the results of a radon test? 

• What are the symptoms of radon poisoning? 

• Does Florida have radon?

• Where does radon come from? 

• For how many years does an old radon test result remain valid?

• Should homeowners get a pre-listing radon test before selling their home?

• What are a homebuyer's options when the radon test comes back high (4.0 pico-curies/liter or more)? 

• Do granite countertops emit radon?

• How can I tell if a house has a radon mitigation system? 

• Can a mobile/manufactured home have a high radon problem?

• Do I need to test for radon when buying a condominium? 

• What does a radon mitigation contractor do to lower the radon level in a home?

• How can not testing for radon be an expensive mistake for homebuyers?  

• What is radon? Should I be concerned about it?

• Should I buy a house with a high radon level? 

• What is the average radon level of indoor and outdoor air in America?

• What is the operating cost of a radon mitigation system? 

• Should I buy a house with a radon mitigation system?

• Does the buyer or seller of a home pay for radon mitigation when the radon test comes back high? 

• What is the probability of having high radon in a Florida house?

• How quickly do I need to reduce a high radon level in my house? 

• Does a home inspector check for radon?

• What are the problems with underground return air ducts? 

• What is the probability of having high radon in a Florida house?

• What factors can change radon test levels up or down?

    Visit our RADON page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.