ISO 8573-8:2004

Overview

ISO 8573-8:2004 defines standardized test methods for determining solid particle content by mass concentration in compressed air. It specifies sampling techniques, measurement procedures (primarily gravimetric), limits and treatment when water or oil are present, uncertainty considerations and required reporting. The results produced by ISO 8573-8 are suitable for assigning compressed air purity classes in accordance with ISO 8573-1.

Key topics and technical requirements

• Scope: Determines mass concentration of solid particles (mg/m3) with maximum particle-size limits; complements particle-counting methods in ISO 8573-4.
• Measurement method: Gravimetric collection on a hydrophobic membrane (membrane holder required). Mass concentration calculated from mass difference (before/after sampling) divided by sampled air volume.
• Sampling: Performed at or near system pressure, at constant flow rate. Choice of full- or partial-flow methods depends on contamination level and flow; gravity can bias partial-flow sampling for large particles.
• Equipment & instrumentation:
  • Hydrophobic, high-efficiency membrane holder
  • Fine-adjustment flow control valve and calibrated flowmeter (±5% accuracy)
  • Pressure gauge (±2% accuracy) and thermometer (±1 °C)
  • Optional heater to reduce liquid water/oil content prior to sampling
• Limits for liquid contaminants: For reliable gravimetric analysis, liquid water and oil must be minimized - typically <20 mg/m3 for Method A and <5 mg/m3 for Methods B1/B2.
• Sample handling: Dry membranes in a desiccator (silica gel) 10–15 min; if oil/water present, use sulphuric acid desiccation and solvent wash procedures before reweighing.
• Performance & uncertainty:
  • Target mass on membrane: about 1–5 mg per 1 cm2
  • Mass-measurement uncertainty better than ±2%
  • Total authorized result uncertainty: ±10%
• Reference conditions: Results reported at 20 °C, 1 bar(a), 0% relative water vapour (recalculate for actual pressure/temperature/humidity).
• Reporting: Test report must describe system conditions (flow, time, pressure, temperature, contaminants), sampling point, equipment and calibration, and include the phrase “Declared solid particle mass concentration in accordance with ISO 8573-8”.

Applications and who uses it

• Facilities that require documented compressed air quality: pharmaceutical, food & beverage, electronics manufacturing, medical gas systems, and other industries sensitive to particulate contamination.
• Test labs, compressor and filtration manufacturers, maintenance teams, quality managers and auditors who validate compressed air purity or certify compliance with ISO 8573 purity classes.

Related standards

• ISO 8573-1 - Contaminants and purity classes (use to assign class from measured values)
• ISO 8573-4 - Particle-counting test methods (number-based particle sizing)
• ISO 8573-2 - Aerosol oil test methods (sampling hardware references)

Keywords: ISO 8573-8, compressed air, solid particle mass concentration, gravimetric method, sampling techniques, air purity, ISO 8573-1.