Radon Testing Information

The following guidelines are condensed from the most recent U.S. EPA radon testing protocols.

When to test?

You may use this test during any season, as long as closed building conditions can be maintained. All external doors, windows, and vents should be kept closed from 12 hours before starting the test until the end of the test. You don’t need to change your normal entry and exit routines, just make sure you close the door behind you. If the building has a permanently installed radon mitigation system, air to air heat exchanger, and/or combustion air supplies for furnaces, etc., they should be operated normally. However, do not operate any whole house or window fans during the test. This test should not be started if severe weather is predicted. For example, a major storm system with winds exceeding 30 miles per hour.

How long to leave the sampler in place?

This sampler is designed to be exposed 72 to 168 hours (three to seven days). This means you must leave it in place for at least 3 days. You may expose it up to 7 days if you are not testing in a humid environment (over 55% relative humidity). Either way, your test result will be an average of approximately the last 4 days of the exposure period.


Test the lowest area of the building that is used on a regular basis. EXCEPTION: Citizens of Pennsylvania are required to test the lowest LIVABLE area of the building. This is especially important if only one test is being conducted, or if this is a follow-up test to confirm the need to mitigate for radon. Place it where it will not be disturbed. The preferred method is to hang the sampler centrally in the room. Use one sampler for every 2000 square feet of floor space being tested. It should be within the normal breathing zone (2 to 6 feet from the floor). The sampler may be hung from an interior non-masonry wall as long as the opening is not blocked (at least 4 inches clearance) and it is facing toward an open area of the room. String may be useful to hang the kit from the ceiling or light fixture. DO NOT place it in a draft. Keep it 3 feet or more from doorways, hallways, windows, exterior walls, and heating or air-conditioning vents. Do not place it in the same room with any type of operating fan or blower. Air blowing on or near an activated charcoal sampler may increase its sensitivity to radon. DO NOT place it near any heat source such as a stove, fireplace, or baseboard heater. Keep it out of direct sunlight. Heat may reduce the sensitivity of some radon measurement devices. DO NOT test areas of high humidity, such as bathrooms, kitchens, laundry rooms, closets, or damp basements. If you must test a damp or humid room (over 55% RH), then test only for the shortest recommended period. Moisture may reduce the sensitivity of some radon measurement devices. DO NOT place this sampler within 3 feet of another activated charcoal device. (Exception: you may place two of the same type and model of test device within 12 inches of each other when conducting a Quality Control audit or when testing for a real estate transaction).