Researchers in Germany compared two devices used to measure the size and number of particles in the air. They found that one device, the Partector Pro, gave accurate results for small particles but had some differences for larger particles. The total number of particles measured by the Partector Pro matched well with the other device. The average size of particles measured by the Partector Pro was mostly accurate, especially for particles between 20 and 50 nanometers. Overall, the Partector Pro performed well for common particle sizes, but had some limitations for larger particles and varied particle distributions.