Authorities in a Howard County, Md., circuit court recently turned to a chocolate Labrador–mix named Barney to solve a puzzle. Except Barney's case wasn't a crime: He helped them find mold lurking in the walls of the courthouse. Barney is one of dozens of canines trained in mold detection. A former pound puppy, he received close to 1,000 hours of training at the Florida Canine Academy. His handlers, David and Rondra Marcelli, were certified after a 60-hour class. About 50 dog handlers in the United States are certified in mold-detection services.

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