Chapter 5 - Quality Assurance & Quality Control
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Non-Interference Methods

There are many ways to protect the test environment. Some methods or protocols are mandatory while others are simply best practice. Professionals who approach the radon measurement process with a comprehensive approach and a goal of quality and accuracy will often employ multiple methods that complement each other. Check with your state to ensure you are employing methods of protecting the test environment that comply with your state regulations.

At a minimum, the following measures must be taken to promote non-interference with the measurement:

Prior Notification

  • Written Instructions The person responsible for the home must be provided written instructions regarding required test conditions, information about closed-building conditions and key compliance issues. Prior to scheduling a radon measurement, a consultation with the homeowner, occupant, controlling party or builder is essential to protecting the test environment, especially when testing a home involved in a real estate transaction. The measurement professional should take this opportunity to educate the homeowner/agent/builder on the mandatory closed-building conditions and obtain a signature on the non-interference agreement.  It is also wise for the measurement professional to obtain a general idea of how the property will be used during the measurement period.   This conversation can help avoid potential interference by third parties such as building contractors, houseguests, housekeepers, etc., which can cause delays in closing.
  • Radon-Test-In-Progress – A radon Test-In-Progress notification should be placed at every entrance/exit of the property in a highly visible area.  Doorknob placards, laminated signs affixed with tape, or extra – large sticky-type notes are all good examples of test notification signage.
  • Non-Interference Agreement [NIA]– to obtain a signed non-interference agreement (NIA) (or compliance agreement) by the seller or controlling party of the property when testing in a real estate transaction.  The NIA serves as a binding contract in which the seller or controlling agent agrees to comply with test conditions and indicates an understanding of the consequences of violating the agreement. Therefore, it is important that a non-interference agreement specifically outlines the legal and financial ramifications of any interference.
  • Radon Information – Consumers should be provided information for obtaining state-specific or EPA information about radon.

Post-Test Verification

A thorough inspection of the property should be conducted upon device retrieval to ensure closed-building conditions were not violated or to detect other manners of interference. As a best practice, professionals should verify that:

  • Closed-building conditions are still in effect
  • Dectectors have not been moved or tampered with
  • Tamper seals on windows are intact [when used]
  • HVAC and other ventilation/circulation appliances are operating according to set procedures
  • Other non-interference measures have not been compromised

The following examples of non-interference methods are complementary options to the mandatory methods previously listed:

Tamper Tape

A specially formulated tape is readily available for purchase by radon professionals.  This tape can serve as a first line of protection against interference in particularly difficult situations such as multi-family dwellings, homes involved in a real estate transaction, etc. It should be noted that tamper tape is not a fail-safe method for ensuring closed-building conditions are maintained. Tamper seals are often broken during the home inspection. As well, it is a common practice for tamper seals to be affixed solely on lower level windows. This often gives the homeowner a false message that only lower-level windows should remain closed. 


Strategically placed business cards, carrying cases, and painter’s tape are excellent choices to mark the original location of monitor placement or compliance notifications. Common sense and innovation are wonderful complements to a comprehensive system.