This SAE Recommended Practice describes uniform laboratory techniques for employing the constant volume sampler (CVS) system in measuring various constituents in the exhaust gas of gasoline engines installed on passenger cars and light trucks. The techniques described relate particularly to CVS systems employing positive displacement pumps. In some areas of CVS practice, alternate procedures are given as a guide toward development of uniform laboratory techniques. The report includes the following sections: 1. Introduction 2. Definitions 3. Test Equipment 3.1 Sampler 3.2 Bag Analysis 3.3 Modal Analysis 3.4 Instrument Operating Procedures 3.5 Supplementary Discussions 3.6 Tailpipe Connections 3.7 Chassis Dynamometer 4. Operating and Calibrating Procedure 4.1 Calibration 4.2 Operating Procedures 5. Data Analysis 5.1 Bag Analysis 5.2 Modal Analysis 5.3 Background 5.4 Fuel Economy 6. Safety