This module, one of 25 on vocational education training for careers in environmental health occupations, contains self-instructional materials on operating gas-absorbing equipment. Following guidelines for students and instructors and an introduction that explains what the student will learn are three lessons: (1) identifying parts and functions of each component in a gas-absorbing sampling train; (2) cleaning and calibrating a gas-absorbing sampling train; and (3) operating a gas-absorbing sampling train to obtain an enclosed area sample for analysis of sulfur dioxide. Each lesson contains objectives, recommended methods and location for practice, performance criteria, equipment and supplies to perform a task, detailed step-by-step instructions for learning a task, and performance exercises. Performance tests cover the subject matter of each lesson. (CT)