This learning module, one in a series of 20 related training modules for apprentice stationary engineers, deals with air compressors. Addressed in the individual instructional packages included in the module are types of air compressors and the maintenance and operation of air compressors. Each instructional package in the module contains some or all of the following: a lesson goal, performance indicators, a study guide, a vocabulary list, an introduction, instructional text, an assignment, a job sheet, a self-assessment activity, a post-assessment instrument, answers to the post-assessment instrument, and a list of recommended supplementary references. (MN)