Page 23 - Fall 2011

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LHI Analytical
P.O Box 941
Pennington, NJ 08534
There are many options for testing radon in homes. The devices below are used for short term
and long term testing. If you are considering doing a radon test of your home you should only
hire a licensed radon testing firm. The testing firm should only test for radon and not do
mitigation. This is considered a conflict of interest. Charcoal canisters are the most widely used
do to the fact in most cases the testing company only has licensed technicians on staff. The
canisters are sent out to a licensed testing lab for analyses. To analyze devices the testing
company must have a licensed as a testing business. LHI Analytical is one of four inspection
firms in NJ to be licensed as a testing business.
1.AC - Activated Charcoal Absorption
For this method, an airtight container with activated charcoal is opened in the area to be
sampled and radon in the air adsorbs onto the charcoal granules. At the end of the sampling
period, the container is sealed and may be sent to a laboratory for analysis.
The gamma decay from the radon adsorbed to the charcoal is counted on a
scintillation detector and a calculation based on calibration information is
used to calculate the radon concentration at the sample site. Charcoal
adsorption detectors, depending on design, are deployed from 2 to 7 days.
Because charcoal allows continual adsorption and desorption of radon, the
method does not give a true integrated measurement over the exposure time. Use of a
diffusion barrier over the charcoal reduces the effects of drafts and high humidity.
2. AT - Alpha Track Detection (filtered)
For this method, the detector is a small piece of special plastic or film inside a small container.
Air being tested diffuses through a filter covering a hole in the container. When alpha particles
from radon and its decay products strike the detector, they cause damage tracks. At the end of
the test the container is sealed and returned to a laboratory for reading.
The plastic or film detector is treated to enhance the damage tracks and
then the tracks over a predetermined area are counted using a microscope
or optical reader. The number of tracks per area counted is used to
calculate the radon concentration of the site tested. Exposure of alpha track
detectors is usually 3 to 12 months, but because they are true integrating
devices, alpha track detectors may be exposed for shorter lengths of time when they are
measuring higher radon concentrations.