Compressed air is often referred to as the “fourth utility” in manufacturing, yet it is also one of the most misunderstood. While pressure and flow typically receive the most attention, air purity is just as critical, and can be costly or even dangerous when it is overlooked. The VDMA 15390‑1 specification was created to help bridge the gap between theory and real‑world industrial practice by translating ISO 8573‑1 into practical guidance for users. For manufacturers looking to implement ISO 8573 purity classes in their manufacturing processes, these VDMA principles are highly relevant.

Understanding What “Compressed Air Purity” Really Means

VDMA 15390‑1 reinforces the ISO 8573‑1 framework, which defines compressed air purity using three core contaminant categories:

  • Particles
  • Humidity or water
  • Oil (aerosol and vapor combined as “total oil content”)

Purity is expressed in a simple three‑digit format: ISO 8573‑1:2010 [P:W:O]. This describes the class for each contaminant. This system ensures that users, equipment manufacturers, and service providers speak the same language when specifying or verifying air quality.

Crucially, VDMA 15390‑1 emphasizes that air purity must be defined at the point of use, not just downstream of the compressor. What leaves the compressor clean does not always arrive clean at the application. Often contamination is introduced down the line via leaks, maintenance, or even equipment malfunction.

Compressed Air Contamination Sources

One of the document’s most valuable contributions is its explanation of how contaminants behave inside a compressed air system. Water and oil can exist simultaneously as vapor, aerosol, or liquid, changing state with pressure and temperature fluctuations. Particles enter not only from ambient intake air but also from corrosion, abrasion, sealants, and even treatment equipment itself.

Water is identified as a significant threat. Once air cools after compression, excess moisture condenses, leading to corrosion, microbial growth, frozen lines, and damaged equipment. The guideline’s rule of thumb is to maintain a pressure dew point at least 10°C below the lowest ambient temperature.

Typical Air Quality Depends on the Application

VDMA 15390‑1 does not attempt to impose one “ideal” purity level. Instead, it provides extensive examples of typical purity classes by industry and application. The document recognizes that different applications and different systems will have varying requirements and capabilities.

For example:

  • Control and instrument air generally require moderate particle control, limited humidity, and manageable oil levels.
  • Process air, especially when it comes into direct contact with products, demands higher purity, often requiring oil‑free and very dry air.
  • Sensitive industries such as food, beverage, and pharmaceuticals are addressed in companion documents with even stricter requirements.
  • This application‑driven approach helps users balance reliability, quality, and energy efficiency.

Treatment Components Must Work as a Chain

VDMA 15390‑1 stresses that compressed air treatment is not a single device but a treatment chain. Each component, including water separators, dryers, filters, activated carbon adsorbers, have defined capabilities and limitations. Some devices require pre‑treated air to function correctly, and improper sequencing can quickly compromise performance.

Importantly, filter labels such as “1 µm” or “0.01 µm” are described as historical shorthand rather than performance guarantees. Real separation efficiency depends on flow rate, pressure, and inlet conditions, reinforcing the need for proper system design rather than isolated component selection.

Monitoring, Maintenance, and Cost Awareness

Achieving compressed air purity is only half the battle but maintaining it is an ongoing challenge. VDMA 15390‑1 outlines both indirect verification (based on proper treatment and maintenance) and direct measurement using standardized ISO test methods.

Regular maintenance and routine compressed air quality testing are non‑negotiable. For example, something like a clogged filter can increase pressure drops, directly translating into energy waste. If the substance clogging the filter is knocked loose, or sheds, then the air downstream and ultimately the product will become contaminated. In other words, neglected air quality quite literally costs “hard cash.”

A Practical Guide for Air Quality Testing, Not Just a Standard

VDMA 15390‑1 is an incredible resource because it does not replace ISO standards, it provides real and actionable guidance for manufacturers. By combining technical definitions, application examples, system design principles, and operational guidance, it remains a valuable reference for anyone responsible for compressed air systems.

Clean, dry compressed air is not about perfection; it is about fitness for purpose. And that is the principle VDMA 15390‑1 drives home.