In accordance with an embodiment, a method of monitoring an air flow includes performing a plurality of radar measurements using a millimeter-wave radar sensor with a line of sight having a component perpendicular to a direction of an air flow, detecting an object in the air flow based on the plurality of radar measurements, calculating a displacement of the object and a size of the object based on the plurality of radar measurements, estimating a velocity of the object based on the calculated displacement, and calculating a risk metric based on the calculated size of the object and estimated velocity of the object.