Define the contact condition
Identify whether compressed air directly contacts the product, contacts a product-contact surface, or only operates an isolated actuator. These duties may need different treatment. A pressure-vessel liquid-transfer system can expose the product to the transfer gas, so the quality team should participate in defining the air specification.
Use a measurable specification
ISO 8573-1 provides a framework for classifying compressed-air purity with respect to particles, water and oil. Select the required limits for the application rather than treating one advertised class as universal. If microbiological control is relevant, specify the associated risk assessment, filtration and verification approach as well. A particle or oil class alone is not a complete statement of sterility.
Check the distribution after treatment
Storage vessels, pipework, drains, hoses and point-of-use fittings can affect the delivered quality. Specify where sampling occurs and under what operating conditions. The pressure available after treatment also matters to capacity. A filter that provides the required separation but causes excessive pressure drop may need a different size or maintenance arrangement.
Include maintenance in the supply scope
List filter elements, replacement criteria, differential-pressure indication and drain checks. Agree who verifies the installed quality before production and how it will be monitored. The useful deliverable is a maintained air-quality system with records, not only a filter model on a quotation. Confirm the plant standard and local requirements during project engineering.
Further reading
General engineering guidance. Numerical examples are illustrative; project specifications and acceptance criteria are agreed for the actual duty.