Mold Comes up on Radar

August 14, 2006
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Researchers test the feasibility of using radar technology to detect mold behind gypsum wallboard. They are using a signal processing algorithm and high-sensitivity, laboratory-size radar system recently developed by the Georgia Tech Research Institute. (Photo by Gary Meek)

Mold growth, like cancer, can be silent, invisible, and deadly. When it comes to mold detection, what a person doesn't know can hurt them. Visible mold is often easy to recognize and can be relatively simple to remediate. Hidden mold, however, is another story.

Georgia Tech Research Institute (GTRI), Atlanta, recently conducted a study promoting new technology for hidden mold detection. Funding for this project was provided by the U.S. Department of Housing and Urban Development's (HUD) Office of Healthy Homes and Lead Hazard Control; the Air Conditioning and Refrigeration Technology Institute Inc. (ARTI); the Office of the Chief Scientist at Georgia Tech Research Institute; and Munters Moisture Control Services. Prepared for ARTI, "Portable Mold Sensors: Technical Feasibility and Operational Requirements," summarizes the operational requirements for a new mold detection technology and outlines the technical ability and feasibility of radar technology to detect hidden mold growth accurately and without causing wall damage.

PLAYING HIDE AND SEEK

Finding mold can be a trial for both the inspector and the structure's owner. It does not need light to grow, so it can hide in many places. Knowing where to look for hidden mold is helpful.

One of the largest mold growth concerns is a vapor barrier. Trapping moisture underneath or between surfaces provides an ideal moist environment where mold can easily grow. The backside of wallpaper, drywall, and paneling can yield hidden mold, along with the top of ceiling tiles and the underside of carpeting and padding.

Pipe chases and utility tunnels are also susceptible to hidden mold growth. Condensate drain pans inside air-handling units, porous thermal or acoustic liners inside ductwork, and roof materials above ceiling tiles have proven to be places that hidden mold inhabits.

The mold investigator's principal tools for finding hidden mold are his eyes, nose, and a flashlight. At times, however, heavier equipment is necessary. One such piece of equipment is the borescope. This item is an optical probe inserted through a small hole drilled into a wall. According to the Environmental Protection Agency (EPA), it allows a mold investigator to inspect a small portion of the wall without causing extensive damage.

Other detection hardware can include humidity gauges. High humidity in a building can lead to mold growth. A more common type of equipment used to detect mold is a moisture meter. Areas of moisture are a warning flag for hidden mold because moisture encourages mold growth. This meter typically has a thin probe that can be inserted into building materials or pressed directly against the material's surface. It can be used on carpet, wallboard, wood, brick, and concrete.

While searching for hidden mold, investigators have to be careful. Peeling back suspect wallpaper or cutting out a section of drywall can release multiple mold spores into the air causing a health risk to the inspector and the occupants, not to mention the cosmetic damage that will have to be repaired.

"At present, there are no good instruments for locating hidden mold," explained the GRTI report.

BACK TO THE LABORATORY

Pioneering new tools in the mold detection field has become a necessity as building technology improves. Buildings built today are often so airtight that they maintain a great capacity to trap moisture, which often leads to mold. Scientists at GTRI worked to find better ways to detect this hidden mold.

The lab investigation, conducted by Víctor De Jesús, Ph.D., Gayathri Balasubramanian, Charlene Bayer, Ph.D., Gene Greneker, Lewis Harriman III., Robert Hendry, William Rowland, Greg Showman, Vince Sylvester, and John Trostel, writers of the GTRI report, explored multiple detection techniques during this study. Gamma ray imaging, neutron beam analysis, X-ray imaging, and T-ray imaging have the potential to find mold growth or hidden pockets of moisture.

The report showed, however, that, "These technologies were also found to be costly, and presented safety and portability issues that eliminated them from practical consideration."

Turning their focus to radar, the scientists worked first with a network analyzer. The cost was tremendous and they moved onto testing more high-resolution radar systems. One trial tested a fixed-frequency Homodyne Transceiver System. Multiple tests were conducted with this unit in order to accomplish the extensive calibration necessary.

After multiple trials and calibrations, the team of scientists finally produced the K-Band radar system and an accompanying software program to measure and effectively display the detection data. The radar unit operates at 24.1 GHz and has an output power of 7 milliwatts. According to the report, it is an "improvement" on the Homodyne Transceiver System.

HOW DOES IT WORK?

Once the K-Band radar system had been developed and calibrated, the scientists set to work testing the validity of the information that the unit yielded. Using a section of wallboard, the scientists installed a working electrical outlet and a light switch.

They also attached pipes and 2x4 headers to create radar clutter, sources that could produce false positives in the image data. A mold sample was cut into an approximate 5x5.5 rectangle and inserted into the test wall.

The wall was then completed by covering the back of it with fiberglass insulation. After testing multiple variables, scientists found that the radar could be focused and successfully detect the spots of hidden mold on the back of the test wall.

"GTRI researchers have demonstrated in the laboratory environment that the change in dielectric constant caused by the moisture content of mold can be detected and mapped to the mold's location on the back of the wallboard," said the report.

One drawback in the testing results was that scientists had a difficult time distinguishing between actual mold growth on the wall and the presence of just moisture on the wall.

"The results are primarily a detection of moisture," noted the report. "Additional resources are needed to further optimize the developed techniques to unequivocally distinguish mold growth from moisture alone.

"Preliminary experiments demonstrate that radar technology holds promise for detecting mold, and it may be packaged in the form of a lightweight, portable, and economical instrument."

PRACTICAL APPLICATION

In addition to the radar study conducted, this scientific investigation also established the operating requirements for a portable mold detector.

Lewis Harriman, Mason-Grant Consulting, began an investigation to help researchers and instrument manufacturers understand the environment for portable hidden mold detection technology and its potential users. The study interviewed and worked online with more than 50 professionals who are currently working in the fields of forensic analysis, mold remediation, water damage restoration, building management, environmental health, insurance underwriting, and loss prevention. Harriman and his staff also made multiple site visits.

The study concluded "a mold detector would be useful even if it could only locate the areas of very heavy mold growth because those are the circumstances most likely to generate a large enough problem to involve third parties. In addition, if a portable detector could locate low levels of growth, it would be even more useful."

Publication date: 08/14/2006

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