EPA Radon Testing Recommendations

EPA Recommends -

Measurement Conditions: The following conditions should exist prior and during a measurement periods to standardize the measurement conditions as much as possible. This list may be applied to most of the measurement devices in use today. However, there may also be method–specific conditions that are mentioned in the applicable protocol for testing.

Short term testing

Measurements lasting 90 days or less should be made under closed-building conditions. To the extent reasonable, all windows, outside vents, and external doors should be closed (except for normal entrance and exit) for 12 hours prior to and during the measurement period.

Normal entrance and exit includes opening and closing a door, but an external door should not be left open for more than a few minutes. These conditions are expected to exist as normal living conditions during the winter in northern climates.

In addition to maintaining closed-building conditions during the measurement, closed-building conditions for 12 hours prior to the initiation of the measurement are a required condition for measurements lasting less than four days, and are recommended prior to measurements of up to a week in duration.

Internal-external air exchange systems (other than a furnace) such as high-volume attic and window fans should not be operating during measurements and for at least 12 hours before measurements are initiated. Air conditioning systems that recycle interior air may be operating. Normal operation of permanently installed air-to-air heat exchangers may also continue during closed-building conditions.

In buildings where permanent radon mitigating systems have been installed, these systems should be functioning during the measurement period.

Short-term tests lasting just two or three days should not be conducted if severe storms with high winds (e.g., > 30 mph) or rapidly changing barometric pressure are predicted during the measurement period. Weather predictions available on local news stations can provide sufficient information to determine if these conditions are likely.

For measurements that must be made during the warm season, the closed-building conditions are satisfied by meeting the criteria above. The closed-building conditions must be verified and maintained more rigorously, however, when they are not the normal living conditions.

Measurement Device Location Selection

The following criteria should be applied to select the location of the detector within a room. Remember, there may be method-specific criteria that is not covered here.

A position should be selected where the detector will not be disturbed during the measurement period and where there is adequate space for the device.

The measurement should not be made near drafts caused by heating, ventilating and air conditioning vents, doors, fans, and windows. Locations near excessive heat, such as fireplaces or in direct sunlight, and areas of high humidity should be avoided.

The measurement location should not be within three feet of windows or other potential openings in the exterior wall. If there are no potential openings (e.g., windows) in the exterior wall, then the measurement location should not be within one foot of the exterior walls of the building.

The detector should be at least 20 inches from the floor, and least 4 inches from other objects. For those detectors that may be suspended, and optimal height for placement is in the general breathing zone, such as 6 to 8 feet from the floor.

In general, measurements should not be made in kitchens, laundry rooms, closets, or bathrooms.

Measurement Strategy

The choice of measurement strategy depends upon the purpose of the radon measurement and the type of building where the measurement is made, such as a home, school or workplace. EPA’s recommendations for measuring radon in various situations are outlined in documents such as the second edition of “A Citizen’s Guide to Radon” (U.S. EPA 19992a), the EPA “Home Buyer’s and Seller’s Guide to Radon” (U.S. EPA 1992b), the “Protocols for Radon and Radon Decay Product Measurements in Homes” (U.S. EPA 1992c).