ISO 8573-1 is the international standard that defines compressed air quality, classifying its purity based on three contaminants: solid particles, water, and oil. It establishes a series of numbered classes that allow for the objective and measurable specification of how clean the air must be for each industrial application. In other words, it is the common language that manufacturers, installers, and users rely on to understand one another when discussing “clean air.”
Understanding this standard is key, because not all industries require the same quality of compressed air. The air that powers an air gun in a workshop does not have the same requirements as air that comes into contact with food or medical instruments. ISO 8573-1 clarifies these differences, prevents costly misunderstandings, and determines what compressed air treatment each facility needs to achieve the required purity.
What contaminants does the ISO 8573-1 standard measure?
The air drawn in by a compressor is, quite simply, ambient air, and impurities enter along with it that must be controlled. The standard focuses on the three types of contaminants that affect any pneumatic system:
Solid particles. Dust, pollen, and debris carried in the intake air, as well as rust particles that may be generated by a deteriorated piping system. They are classified according to their size and concentration.
Water. Moisture in the air condenses when the air is compressed and appears as vapor or liquid within the network. It is the most common contaminant and the one that causes the most damage: corrosion, frozen lines, and the proliferation of microorganisms. It is measured by the dew point.
Oil. It comes from both the ambient air and the lubrication of certain compressors. It is measured as total oil concentration (aerosol, liquid, and vapor) and is critical in industries where the air comes into contact with the final product.
Compressed Air Quality Classes According to ISO 8573-1
For each of the three contaminants, the standard defines a scale of purity classes. The lower the class number, the more stringent the cleanliness level. An air quality specification is expressed by combining the three classes, in the order of particulates, water, and oil.
| Class | Solid particles | Water (dew point) | Total oil |
|---|---|---|---|
| Class 0 | More stringent than Class 1, according to the manufacturer’s specifications | More demanding than Class 1 | More demanding than Class 1 |
| Class 1 | Minimum amount of very fine particles | Dew point ≤ -70 °C | ≤ 0.01 mg/m³ |
| Class 2 | Very fine particles in low concentrations | Dew point ≤ -40 °C | ≤ 0.1 mg/m³ |
| Class 3 | Fine particles | Dew point ≤ -20 °C | ≤ 1 mg/m³ |
| Class 4 | Larger particles | Dew point ≤ +3 °C | ≤ 5 mg/m³ |
| Lesson 5 | Higher particle concentration | Dew point ≤ +7 °C | Not specified in this class |
| Lesson 6 | Basic level of filtration | Dew point ≤ +10 °C | — |
Thus, air specified as “ISO 8573-1 Class 1.2.1” indicates Class 1 for particles, Class 2 for water, and Class 1 for oil. This method of specifying quality is the one used in technical specifications, audits, and installation projects.
What Kind of Air Does Each Industry Need?
The appropriate class depends entirely on the application. General-purpose applications, such as pneumatic tools or blowing air in workshops, work well with intermediate classes. In contrast, sectors where air comes into direct contact with the product require the highest classes. Compressed air for the food industry is the clearest example: air used in packaging, blowing out containers, or transporting ingredients must be virtually free of oil and moisture so as not to compromise product safety. Other sectors with high requirements include pharmaceuticals, healthcare, electronics, and automotive painting.
How Each Class of Compressed Air Quality Is Achieved
Achieving the purity class specified by the standard depends not only on the compressor, but above all on the subsequent air treatment. Each contaminant is removed using specific equipment: filters trap particles and oil aerosols, dryers (refrigerated or adsorption) reduce humidity to the required dew point, and drains remove accumulated condensate. Combining these elements in the correct order achieves the exact level of quality that each installation requires. That is why air treatment is the factor that truly determines whether or not a system complies with ISO 8573-1.
Where to find the complete ISO 8573-1 standard
The ISO 8573-1 standard is an official document published by the International Organization for Standardization (ISO). The full text is not available for free download: it can be purchased through the official ISO website or through each country’s standards organization (in Spain, UNE). The tables and classes summarized in this article include the most commonly referenced parameters, which are sufficient to specify air quality in most projects without needing to consult the full document.
Ensure the air quality in your facility with Jender
Compliance with ISO 8573-1 isn’t just a matter of a single piece of equipment; it’s about designing the entire system with the purity class your process requires in mind. At Jender, we design, install, and maintain compressed air systems with filtration and drying solutions tailored to each industry, offering technical service throughout Spain 365 days a year. Tell us about your process, and we’ll help you determine the air quality you need and how to achieve it.
