In the “Consumer’s Guide to Radon,” the EPA offers a Radon Testing Checklist, which states: For reliable test results, follow this Radon Testing Checklist carefully. Testing for radon is not complicated. Improper testing may yield inaccurate results and require another test. Disturbing or interfering with the test device, or with closed-house conditions, may invalidate the test results and is illegal in some states. If the seller or qualified tester cannot confirm that all items have been completed, take another test.

Before Conducting a Radon Test:

• Notify the occupants of the importance of proper testing conditions. Give the occupants written instructions or a copy of this Guide and explain the directions carefully.
• Conduct the radon test for a minimum of 48 hours; some test devices have a minimum exposure time greater than 48 hours.
• When doing a short-term test ranging from 2-4 days, it is important to maintain closed-house conditions* for at least 12 hours before the beginning of the test and during the entire test period.
• When doing a short-term test ranging from 4-7 days, EPA recommends that closed-house conditions be maintained.
• If you conduct the test yourself, use a qualified radon measurement device and follow the laboratory’s instructions. Your state may be able to provide you with a list of do-it-yourself test devices available from qualified laboratories.
• If you hire someone to do the test, hire only a qualified individual. Some states issue photo identification (ID) cards; ask to see it. The tester’s ID number, if available, should be included or noted in the test report.
• The test should include method(s) to prevent or detect interference with testing conditions or with the testing device itself.
• If the house has an active radon-reduction system, make sure the vent fan is operating properly. If the fan is not operating properly, have it (or ask to have it) repaired and then test.
• *Closed-house conditions means keeping all windows closed, keeping doors closed except for normal entry and exit, and not operating fans or other machines which bring in air from outside. 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. 

During a Radon Test:

• Maintain closed-house conditions during he 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, operate only air-conditioning units which 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.

After a Radon Test:

• If you conduct the test yourself, be sure to promptly return the test device to the laboratory. Be sure to complete the required information, including start and stop times, test location, etc.
• If an elevated level is found, fix the home. Contact a qualified radon-reduction contractor about lowering the radon level. EPA recommends that you fix the home when the radon level is 4 pCi/L or more.
• Be sure that you or the radon tester can demonstrate or provide information to ensure that the testing conditions were not violated during the testing period.