The USEPA Protocols for Radon and Radon Decay Product Measuments in Homes specify the “Closed Building Measuements” that are to be maintained before and during radon tests as follows:

Conduct the radon test for minimum of two days..

• In homes with an active radon reduction system, check that the fan is running at least 24 hours before starting a short-term test lasting less than four days. Air exhaust fans that typically
operate for short periods (e.g., bathroom fan) may be used during the test.

• EPA recommends that short-term radon testing, which lasts for no more than a week in length, be dne under closed-building conditions. Closed-building conditions means keeping all
windows closed, keeping doors closed except for normal entry and exit, and not operating fans or other machines that bring in air from outside. Note that fans that are part of a radon reduction system or small exhaust fans operating for only short periods of time may run during the test.

• When doing short-term testing lasting less than four days, it is important to maintain closed building conditions for at least 12 hours before the beginning of the test and for the entire test period. Do not operate fans or other machines that bring in air from the outside.

During the radon test:

• Maintain closed-building conditions during the entire time of a short-term test, especially for tests shorter than one week in length.

• Operate the home’s heating and cooling systems normally during the test. For tests lasting less than one week, only operate air conditioning units that recirculate interior air.

• Do not disturb the test device at any time during the test.

• If a radon reduction system is in place, make sure the system is working properly and will be in operation during the entire radon test.