Abstract: This method and device collect relative humidity data, then evaluate that data using an algorithm to determine if conditions are permissible for fungal growth. The growth condition meter, placed in a building's wall or ceiling, includes a simple controller attached to a memory, a timer, a relative humidity sensor, and a user interface. The device executes an algorithm for determining growth conditions based on a 24-hour history of relative humidity samples. First, the algorithm determines if relative humidity levels follow a cyclical profile similar to typical environmental conditions. In addition, it verifies that enough time is spent below a temporal humidity threshold. Second, the algorithm performs a baseline analysis comparing all samples over the previous 24-hour period to determine if all samples are over a fixed threshold. This allows for a situation where enough time is spent below the temporal threshold but overall relative humidity remains too high.