Testing Equipment
Radon Reduction uses three types of testing equipment. The
following is information about each.
CONTINUOUS MONITOR
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We use a continuous monitor whenever possible. When a
radon atom decays it momentarily increases the conductivity of the air.
Our continuous monitor uses this to count radon decays in an active
volume. It only takes only an hour or so for the air in the monitor to
equilibrate with the room air. Once that has occurred, the monitor
accurately evaluates the air radioactivity. The continuous monitor has a built-in data logger and records the radon every half hour. (It doesn’t really record the time of each decay-which would make it really continuous-but records the number of counts each half hour.) This time record provides automatic quality assurance in the measurement. You can see the measurement levels vary according to standard sampling statistics as expected. You can also usually see the day to night variation that results from the stack effect. Occasionally, you can see household activities that increase the influx of radon. An extreme example of this would be starting a fire in a wood stove while a gentler source would be turning on a clothes drier. One type of continuous monitor is the femto-Tech |
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CHARCOAL CANISTERS
We use charcoal canisters for additional measurements.
These are small canisters that contain activated (clean) charcoal (almost
pure carbon). Impurities in the air will adsorb (adhere) to the carbon according
to a partition constant. We know that the radon in the air of a room will
partition between the gas phase and the phase stuck to the carbon surface with a
certain time constant. After the canister is opened and exposed to the air of
the room for a certain period of time, the number of atoms of collected radon
may be carefully measured (assayed) with radiation detection crystals. The time
of collection is recorded and since the assay time is also known, an accurate
estimate of the average radon in the room air may be calculated. Since radon
levels go up and down, you can see that this type of measurement is biased
towards the conditions at the end of the measurement period. Nevertheless, these
are economical devices and provide good data.
ALPHA-TRACK DEVICES
We use alpha-track devices for long-term measurements. These are nothing more than a fancy holder for a small piece of photographic film. When a radon atom decays near the film, the alpha particle so produced can make a “track” on the surface of the film. By evaluating the density of tracks on the film and correlating this with the length of time it is exposed, one can get an accurate estimate of the average ambient radon. To get enough tracks for good sampling statistics, the film should be exposed for a relatively long period of time. We use alpha tracks for measurements of three months to one year.
