What does it mean that compressed air quality complies with ISO 8573-1: Class 4?

What is it? ISO 8573-1 standard?

ISO ISO 8573-1 is the core international standard developed by the International Organization for Standardization that specifies the quality of compressed air. This standard quantifies the three primary contaminants in compressed air—Solid particles,Moisture (Humidity)andOil content, air quality is classified into distinct purity levels. This classification system provides industrial users with a clear reference for selecting, designing, and validating compressed air systems.

Class 4 Specific technical specifications

When it comes to compressed air quality reaching “ Class 4 ” at that time, it usually refers to the concentration of pollutants in the air being limited to ISO Within the Level 4 range specified in Standard 8573-1. Specifically with regard to the three major pollutants, Class 4 The technical specifications are as follows:

• Solid particles: In every cubic meter of air, the number of particles ranging from 0.1 to 0.5 micrometers shall not exceed 400,000; the number of particles ranging from 0.5 to 1.0 micrometers shall not exceed 6,000; and the number of particles ranging from 1.0 to 5.0 micrometers shall not exceed 100.
• Moisture (pressure dew point)The pressure dew point (PDP) of compressed air shall not exceed +3°C. This means that under the system’s operating pressure, the temperature drops to +3°C Condensation will only occur at that time.
• Oil content: The total oil content (including liquids, aerosols, and oil vapors) shall not exceed 5 mg/ m³.

Class 4 Applications of Compressed Air

Class 4 It falls within the mid‑range purity category for compressed air quality. While it cannot meet the stringent oil‑ and water‑free requirements of industries such as food processing, pharmaceuticals, or precision electronics manufacturing, it offers exceptional cost‑effectiveness and practicality in many conventional industrial applications.

Typical application scenarios include:

• Drive for conventional pneumatic tools and pneumatic actuators.
• Part blowing and cleaning in typical industrial environments.
• Cooling and chip evacuation in non-precision machining.
• Conventional packaging machinery and material handling systems.

How to achieve and maintain Class 4 Standard

To ensure the compressed air system stably delivers compliant output… Class 4 Standard gases typically require the installation of appropriate post-treatment equipment:

• Filtration systemInstall multi-stage filters (such as coarse- and high-efficiency filters) to capture solid particles and liquid oil droplets in the pipeline, ensuring that particulate matter and oil content meet the specified standards.
• Drying equipment: Configure the refrigerated air dryer. Due to Class 4 The requirement for the pressure dew point is +3°C, Refrigerated air dryers can typically control the dew point within this range in a cost-effective manner.
• Regular maintenanceRegularly replacing filter elements, draining condensate, and inspecting the dryer’s operating condition are essential to prevent air quality degradation and maintain… Class 4 The key to the standard.