Source-capture air cleaners use multiple filters to remove aerosols, droplets, and other airborne contaminants from the air in labs, dentist's offices, and similar locations. They have a movable, self-supporting extractor arm that can be positioned close to the source of the contaminated air so the air can be extracted before the contaminants spread away from the source. An optional grated cover can be installed on an air cleaner's inlet to convert the air cleaner to a downdraft system that draws in airborne contaminants during sanding, grinding, and other finishing work to help prevent nearby workers from breathing them in.