What Do Eyeglasses and Radon Detectors Have in Common? The Science Behind Alpha Track Radon Detectors
The gold standard for radon measurement lies within a small plastic chip that can fit in the palm of your hand.
Of all the radon measurement techniques used worldwide, alpha track radon detectors that use CR39 plastic chips are the most widely used.
What is CR39 plastic?
CR39 means “Columbia Resin #39” and is plastic made from polyallyl diglycol carbonate, or PADC. Columbus Chemical Industries developed the plastic in 1940 as the 39th formula in their series of polymer experiments, hence the name “CR39”. It was first used during World War II in glass-enforced plastic fuel tanks of bomber aircraft to provide durable and lightweight fuel tank liners.
Today it is commonly used in eyeglass lenses and can be found in airplane windows,bullet-resistant windows, medical implants and prosthetics, and other optical devices such as camera and projector lenses. CR39 plastic is also used for the detection of ionizing radiation.
How do alpha track radon detectors work?
An alpha track detector consists of a small plastic chamber that houses a CR39 plastic film/chip. As radon enters the chamber it emits alpha particles from its decay products. These particles damage or “strike” the CR39 plastic and etch scratches in the film.Under a microscope these scratches look like tiny tracks. This is where we get the term “alpha track detectors”, also known as ATDs.
After the measurement period of 90 to 365 days, an alpha track detector is sent to a lab where the plastic film is removed from the housing. The plastic film is then examined under a microscope where the “scratches” or tracks in the plastic are counted. The number of tracks, along with considering the chamber size and test duration, are used to calculate the radon concentration during the exposure period.
CR39 detectors are also known as solid state nuclear track detectors (SSNTD). The number, size, and shape of the tracks provides information about the mass, charge, motion, and direction of the particles. The devices can record alpha tracks for up to a year which provides a precise long-term radon measurement.
Long-term radon detectors
A long-term alpha track radon detector, such as the Radtrak, can be deployed for 90 days up to one year. A long-term radon test provides the most accurate result for the average radon level in a home or building. Radon varies over time, from day to day and even hourly. Long-term radon tests can account for these variations and still calculate a reliable annual radon average. The longer you test, the more accurate your result.
A simple and powerful radon detector
Alpha track radon detectors are not affected by environmental factors such as gamma radiation or humidity, making them a reliable choice. They are also cost effective with no requirement for batteries or a power source. You just set the detector in place and leave it alone while it passively collects radon data.
With their economical cost and robustness, alpha track detectors with CR39 plastic are still the most widely used method of detecting radiation from radon exposure.
Radon is the #1 cause of lung cancer in nonsmokers and the #2 cause of lung cancer after smoking. Radon is an odorless, colorless gas that enters your home through cracks in the foundation, basement walls, floor joints, sump openings, and drains. Once inside your home, especially an energy-efficient home, radon becomes trapped where you can inhale it into your lungs. Over time, radon exposure can cause lung cancer. Having the most accurate radon test result is critical so that you can assess the lung cancer risk for both you and your family.
