The document discusses the importance of performing baseline emission tests before and after vehicle repairs using various equipment such as a 5-gas analyzer, scope, scan tool, or DVOM. A baseline test involves monitoring the 5 regulated emissions gases at idle, 3000 RPM, and two modes of the Accelerated Simulation Mode to establish a starting point for emissions levels. Comparing the before and after repair baseline readings allows technicians to determine if a repair was successful by calculating the percentage reduction in emissions.