Various embodiments of monitoring systems and methods are disclosed herein to monitor particulate accumulation within a bake chamber configured to thermally treat substrates, and determine when the bake chamber requires cleaning. Embodiments of the disclosed monitoring system may generally include one or more sensors to monitor particulate accumulation on one or more inside surfaces of a bake chamber and/or a bake chamber lid assembly, and a controller, which is coupled to receive a sensor output from the one or more sensors and configured to use the sensor output to determine when cleaning is needed. Various types of sensors including, but not limited to, optical sensors, and surface acoustic wave-based sensors may be used in the present disclosure to monitor particulate accumulation inside the bake chamber.