Short-Term Testing:

The quickest way to test is with short-term tests. Short-term tests remain in your home for two days to 90 days, depending on the device. "Charcoal canisters," "alpha track," "electret ion chamber," "continuous monitors," and "charcoal liquid scintillation" detectors are most commonly used for short-term testing. Because radon levels tend to vary from day to day and season to season, a short-term test is less likely than a long-term test to tell you your year-round average radon level. If you need results quickly, however, a short-term test followed by a second short-term test may be used to decide whether to fix your home.

 

How To Use a Test Kit:

Testing is easy and should only take a few minutes of your time.
Follow the instructions that come with your test kit. If you are doing a short-term test, close your windows and outside doors and keep them closed as much as possible during the test. Heating and air-conditioning system fans that re-circulate air may be operated. Do not operate fans or other machines which bring in air from outside. Fans that are part of a radon-reduction system or small exhaust fans operating only for short periods of time may run during the test. If you are doing a short-term test lasting just 2 or 3 days, be sure to close your windows and outside doors at least 12 hours before beginning the test, too. You should not conduct short-term tests lasting just 2 or 3 days during unusually severe storms or periods of unusually high winds. The test kit should be placed in the lowest lived-in level of the home (for example, the basement if it is frequently used, otherwise the first floor). It should be put in a room that is used regularly (like a living room, playroom, den or bedroom) but not your kitchen or bathroom. Place the kit at least 20 inches above the floor in a location where it won't be disturbed - away from drafts, high heat, high humidity, and exterior walls. Leave the kit in place for as long as the package says. Once you've finished the test, reseal the package and send it to the lab specified on the package right away for analysis. You should receive your test results within a few weeks.

 

Long-Term Testing:

Long-term tests remain in your home for more than 90 days. "Alpha track" and "electret" detectors are commonly used for this type of testing. A long-term test will give you a reading that is more likely to tell you your home's year-round average radon level than a short-term test.

EPA Recommends the Following Testing Steps:

Step 1. Take a short-term test. If your result is 4 pCi/L or higher take a follow-up test (Step 2) to be sure.
Step 2. Follow up with either a long-term test or a second short-term test:
For a better understanding of your year-round average radon level, take a long-term test.

If you need results quickly, take a second short-term test:

The higher your initial short-term test result, the more certain you can be that you should take a short-term rather than a long-term follow up test. If your first short-term test result is more than twice EPA's 4 pCi/L action level, you should take a second short-term test immediately.
Step 3. If you followed up with a long-term test: Fix your home if your long-term test result is 4 pCi/L or more. If you followed up with a second short-term test: The higher your short-term results, the more certain you
can be that you should fix your home.
Consider fixing your home if the average of your first and second
test is 4 pCi/L or higher.
 

What Your Test Results Mean:

Test your home now and save your results. If you find high radon levels, fix your home before you decide to sell it.
The average indoor radon level is estimated to be about 1.3 pCi/L, and about 0.4 pCi/L of radon is normally found in the outside air. The U.S. Congress has set a long-term goal that indoor radon levels be no more than outdoor levels. While this goal is not yet technologically achievable in all cases, most homes today can be reduced to 2 pCi/L or below.
Sometimes short-term tests are less definitive about whether or not your home is above 4 pCi/L. This can happen when your results are close to 4 pCi/L. For example, if the average of your two short-term test results is 4.1 pCi/L, there is about a 50% chance that your year-round average is somewhat below 4 pCi/L. However, EPA believes that any radon exposure carries some risk - no level of radon is safe. Even radon levels below 4 pCi/L pose some risk, and you can reduce your risk of lung cancer by lowering your radon level.
If your living patterns change and you begin occupying a lower level of your home (such as a basement) you should retest your home on that level.
Even if your test result is below 4 pCi/L, you may want to test again sometime in the future.

 

Short-term or long-term measurements should be made in the lowest lived-in level of the house.

The following criteria should be used to select the location of the detectors within a room on this level:

• The measurements should be made in the lowest level which contains a room that is used

regularly. Test areas include family rooms, living rooms, dens, playrooms, and bedrooms. A

bedroom on the lower level may be a good choice, because most people generally spend more

time in their bedrooms than in any other room in the house (Chapin 1974, Moeller and Underhill

1976, Szalai 1972). If there are children in the home, it may be appropriate to measure the

radon concentration in their bedrooms or in other areas where they spend a lot of time, such as

a playroom, that are situated in the lowest levels of the home.

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

measurements should not be made in a kitchen because of the likelihood that an exhaust fan

system and changes in small, airborne particles (caused by cooking) may affect the stability of

WL measurements. Measurements should not be made in a bathroom because relatively little

time is spent in a bathroom, because high humidities may affect the sensitivity of some

detectors, and because of the likelihood that use of a fan may temporarily alter radon or decay

product levels.

Although radon in water may be a contributor to the concentration of airborne radon, radon in air

should be measured before any diagnostic radon-in-water measurements are made. (Diagnostic

measurements may be made in the bathroom; however, such diagnostic measurements should

not be used to determine the need for mitigation.)

• A position should be selected where the detector will not be disturbed during the measurement

period and where there is adequate room 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 heat, such as on appliances, near

fireplaces or in direct sunlight, and areas of high humidity should be avoided.

• Because some detectors are sensitive to increased air motion, fans should not be operated in

the test area. Forced air heating or cooling systems should not have the fan operating

continuously unless it is a permanent setting.

• The measurement location should not be within 90 centimeters (three feet) of the doors and

windows or other potential openings to the outdoors. If there are no doors or windows to the

outdoors, the measurement should not be within 30 centimeters (one foot) of the exterior wall of

the building.

• The detector should be at least 50 centimeters (20 inches) from the floor, and at least 10

centimeters (four inches) from other objects. For those detectors that may be suspended, an

optimal height is in the general breathing zone, such as two to 2.5 meters (about six to eight

feet) from the floor.

Sound judgment is required as to what space actually constitutes a room. Measurements made

in closets, cupboards, sumps, crawl spaces, or nooks within the foundation should not be used

as a representative measurement.

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2.3 Initial Measurements

2.3.1 Rationale

EPA recommends that a homeowner assessing the need for mitigation should first make a short-term

test. Short-term measurements can be simple, produce results quickly, and allow the public to make

decisions about radon reduction that are cost-effective and protective of human health.

The duration of short-term measurements can range from 48 hours to 90 days, depending upon the

method used.

2.3.2 Closed – Building Conditions

Short-term measurements lasting between two and 90 days should be made under closed-building

conditions. Closed-building conditions are necessary for short-term measurements in order to stabilize

the radon and radon decay product concentrations and increase the reproducibility of the

measurement. Windows on all levels and external doors should be kept closed (except during normal

entry and exit) during the measurement period. Normal entry and exit include a brief opening and

closing of a door, but--to the extent possible--external doors should not be left open for more than a few

minutes. In addition, external-internal air exchange systems (other than a furnace) such as highvolume,

whole-house and window fans should not be operating. However, attic fans intended to control

attic and not whole building temperature or humidity should continue to operate. Combustion or makeup

air supplies must not be closed.

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 lasting up to

a week in duration. Normal operation of permanently installed energy recovery ventilators (also known

as heat recovery ventilators or air-to-air heat exchangers) may also continue during closed-building

conditions. In houses where permanent radon mitigation systems have been installed, these systems

should be functioning during the measurement period.

Closed-building conditions will generally exist as normal living conditions in northern areas of the

country when the average daily temperature is low enough so that windows are kept closed. Depending

on the geographical area, this can be the period from late fall to early spring. In some houses, the most

stable radon levels occur during late fall and early spring, when windows are kept closed but the house

heating system (which causes some ventilation and circulation) is not used. Available information about

variations of indoor radon levels in a particular area can be used to choose a measurement time when

the radon concentrations are most stable.

It may be necessary, however, to make measurements during mild weather, when closed-building

conditions are not the normal living conditions. It will then be necessary to establish some more

rigorous means to ensure that closed-building conditions exist prior to and during the measurements.

Those performing measurements in southern areas that do not experience extended periods of cold

weather should evaluate seasonal variations in living conditions and identify if there are times of the

year when closed-building conditions normally exist. Ideally, measurements should be conducted

during those times. The closed-building conditions must be verified and maintained more rigorously

when they are not the normal living conditions. Air conditioning systems that recycle interior air can be

operated during the closed-building conditions when radon measurements are being made. However,

homeowners should be aware that any air circulation system can alter the radon decay product

concentration without significantly changing the radon concentration.

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Short-term tests lasting just two or three days should not be conducted during unusually severe storms

or periods of unusually high winds. Severe weather will affect the measurement results in several ways.

First, a high wind will increase the variability of radon concentration because of wind-induced

differences in air pressure between the building interior and exterior. Second, rapid changes in

barometric pressure increase the chance of a large difference in the interior and exterior air pressures,

consequently changing the rate of radon influx. Weather predictions available on local news stations

can provide sufficient information to determine if these conditions are likely. While unusual variations

between radon measurements may be due to weather or other effects, the measurement system

should be checked for possible problems.

During any short-term test, closed-house conditions should be maintiained as much as possible while

the test is in progress. In test lasting less than four days (96 hours), closed-house conditions should be

maintained for at least 12 hours before conditions should be maintained while the test is in progress;

while recommended, the 12 hour closed-house conditions should be maintained as much as possible

while the test is in progress.

2.3.3 Interpretation of Initial Measurement Results

If the initial measurement result is less than 4 pCi/L, or 0.02 WL, follow-up measurements are probably

not needed. There is a relatively low probability that mitigation is warranted if the result is less than 4

pCi/L or 0.02 WL (EPA 400-R-92-011; U.S. EPA 1992g). Even if the measurement result is less than 4

pCi/L, or 0.02 WL, however, a homeowner may want to test again sometime in the future. If the

occupants' living patterns change or renovations are made to the home and they begin using a

lower level (such as a basement) as a living area, a new test should be conducted on that level.

The average year-round residential indoor radon level is estimated to be about 1.3 pCi/L, and about 0.4

pCi/L of radon is normally found in outside air. The U.S. Congress has set a long-term goal that indoor

radon levels be no more than outdoor levels. There is some risk from radon levels below 4 pCi/L, and

EPA recommends that the homeowner consider reducing the radon level if the average of the first and

second short-term measurements or if a long-term follow-up measurement is between 2 and 4 pCi/L

(0.01 and 0.02 WL). While it is not yet technologically achievable for all homes to have their radon

levels reduced to outdoor levels, the radon levels in some homes today can be reduced to 2 pCi/L or

below.

If the result of the short-term measurement is equal to or greater than 4 pCi/L, or 0.02 WL, the occupant

should conduct a follow-up measurement using a short-term or long-term test, as described in Section

2.4.

 

2.4 Follow-Up Measurements

2.4.1 Rationale

The purpose of a follow-up measurement is to provide the homeowner with enough information to make

an informed decision on whether to mitigate to reduce radon levels. The follow-up measurement,

whether it is short-term or long-term, provides an additional piece of information to confirm that radon

levels are high enough to warrant mitigation. There are two major reasons why a second measurement

is necessary. First and most important, radon levels fluctuate over time (see Section 1), and a second

short-term measurement, when averaged with the first test result, will provide a more representative

value for the average radon level during the period of the test. If a long-term follow-up measurement is

conducted, that result should provide an even more representative value for the long-term average

radon concentration. The second reason for making a follow-up measurement prior to mitigation is that

there is a small chance of laboratory or technician error in all measurements, including radon

measurements, and a second test will serve as a check on the first.

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Homes tested using the protocol in this section should not be mitigated on the basis of a single shortterm

test. A follow-up test is necessary for mitigation decision-making regardless of the initial test result.

2.4.2 Short-Term and Long-Term Follow-Up Testing

Follow-up testing should be conducted in the same location as the first measurement (see Section 2.2).

A follow-up test can be conducted with either a short-term or long-term measurement device. Longterm

tests (> 90 days) will produce a reading that is more likely to represent the home's year-round

average radon level than a short-term test. However, if the initial test result is high (for example, greater

than about 10 pCi/L, or 0.05 WL) or if results are needed quickly, EPA recommends a second shortterm

test. This will allow the homeowners to obtain information necessary to decide quickly on the need

for mitigation. If the result of the initial measurement is between 4 pCi/L and 10 pCi/L (or between 0.02

WL and 0.05 WL), then either a short-term or long-term test can be taken.

If the long-term follow-up test result is 4 pCi/L, or 0.02 WL, or higher, then EPA recommends remedial

action. Likewise, if the average of the initial and second short-term results is equal to or greater than 4

pCi/L, or 0.02 WL, radon mitigation is recommended. These recommendations are summarized in

Exhibit 2-1.

As with the initial short-term test, the second short-term test should be conducted under closed-building

conditions (Section 2.3.2). These conditions, however, are not necessary for long-term tests (those

lasting longer than 90 days).