Measuring air purity at key points in a compressed air system ensures clean, reliable air for all applications. Quality should be checked after filtration to verify that contaminants such as oil, water, and particles are removed. It should also be monitored before distribution points and at critical equipment to ensure that air remains clean throughout the network. The most important location is the point of use, where compressed air directly affects processes and product quality. Regular system wide checks help detect issues early and maintain compliance with required standards.