ISO 8573-4 and Isokinetic Sampling: The Critical Factor for Measuring Particles in Compressed Air
| 25 June, 2026ISO 8573-4 and Isokinetic Sampling
ISO 8573-4 isokinetic sampling is the critical factor that determines whether your compressed air quality measurements are accurate or misleading. Many audits fail not because of the instrument, but because of incorrect sampling conditions. Here’s why.
What is ISO 8573 and Why Does It Matter?
ISO 8573 is the international standard used to classify compressed air quality. Its goal is to define the permitted levels of contaminants within an industrial compressed air system, mainly solid particles, moisture, and oil.
ISO 8573-1: Purity Classification
Establishes the purity classes of compressed air, defining maximum contamination limits permitted according to the industrial application. The pharmaceutical industry requires extremely low levels, while general applications may tolerate higher levels.
ISO 8573-4: Measurement Method
While ISO 8573-1 defines the limits, ISO 8573-4 establishes how particle measurements must be performed: sampling techniques, counting methods, test conditions, and requirements for representative results.
What is Isokinetic Sampling?
Isokinetic sampling occurs when the velocity of air entering the sampling device is exactly equal to the velocity of air flowing inside the main pipeline. Although it may seem like a small detail, it is one of the most important factors for obtaining reliable particle measurements.
⚠ Over-sampling
If the inlet velocity to the sampler is higher than the main flow velocity, more particles than actually present are drawn in — especially large and heavy particles. Results appear falsely high.
⚠ Under-sampling
If the inlet velocity is lower, heavier particles cannot enter the measurement system. The detected concentration is artificially reduced. Results appear falsely low.
Without isokinetic conditions, even the best particle counter can deliver incorrect results.
The Real Challenge in Industrial Plants
In practice, maintaining isokinetic sampling manually is extremely difficult because compressed air systems are constantly changing: pressure variations, flow changes, variable production demand, and fluctuations between the main line and points of use. These conditions continuously modify the flow velocity inside the pipeline, causing many audits to generate inconsistent or poorly repeatable results.
The Solution: SUTO iTEC S600 with Isokinetic Sampling
To solve this problem, SUTO iTEC developed the S600 Portable Compressed Air Purity Analyzer together with a specialized isokinetic sampling device designed in accordance with ISO 8573-4.
What does the S600 measure?
- ✓ Particles
- ✓ Dew point
- ✓ Oil vapor
- ✓ Pressure
- ✓ Temperature
Integrated isokinetic device
- ✓ ISO 8573-4 sampling tube
- ✓ Continuous flow monitoring
- ✓ Needle valve adjustment
- ✓ Real point-of-use simulation
- ✓ Improved repeatability and precision
Key Advantages of the S600
1. All-in-one portable unit
Reduces audit time, connections, and operational complexity. Significantly improves field efficiency.
2. Automatic PDF reports
Ideal for ISO, FDA, QA audits, technical documentation, and internal validations.
3. Intuitive touchscreen
Simplifies configuration, navigation, and guided measurements, reducing human error.
4. Integrated data logger
Stores up to 100 million recorded values for full analysis and traceability.
Industries Where This Is Critical
Pharmaceutical industry
Compressed air may come into direct contact with products, sterile areas, filling systems, and cleanrooms. An incorrect measurement can compromise complete validations.
Food & Beverage
Compressed air is involved in packaging, pneumatic transport, PET lines, and indirect product contact. Contamination can affect quality and food safety.
Electronics
Requires extremely clean environments where microscopic particles can damage sensitive components.
Hospitals & Medical Devices
Compressed air quality is critical for respiratory equipment, hospital systems, and medical manufacturing.
Precision Starts Before the Sensor
The quality of a particle measurement depends not only on the equipment used — it depends on the sampling method. ISO 8573-4 clearly establishes the need for isokinetic conditions to guarantee representative and reliable results. With the SUTO iTEC S600 and its isokinetic sampling device, industries can perform compressed air quality audits with greater precision, repeatability, and regulatory confidence.
