A centrifugal compressor apparatus includes: an impeller mounted for rotation about a central longitudinal axis, the impeller including an impeller disk carrying an array of impeller blades around its periphery; a diffuser disposed downstream of the impeller, configured to diffuse and turn airflow discharged from the impeller; an extraction scoop disposed in fluid communication with the impeller and with a plenum disposed adjacent the impeller, and a dirt collector disposed in fluid communication with the plenum and configured to trap dirt therein.