ISO 8573-5:2001

Overview

ISO 8573-5:2001 - "Compressed air - Part 5: Test methods for oil vapour and organic solvent content" specifies laboratory and field test methods used to detect and quantify oil vapour (hydrocarbons C6+) and volatile organic solvents in compressed air. The standard defines the gas chromatography (GC) procedure as the definitive method, gives guidance on the use of chemical indicator tubes as a preliminary check, and sets out sampling, measurement, evaluation, uncertainty and reporting requirements for determining oil‑vapour concentrations used in compressed air purity classification.

Key topics and technical requirements

• Primary test method: Gas chromatography for oil vapour/organic solvent content. Applicable measurement range (as specified) is approximately 0.001 mg/m3 to 10 mg/m3.
• Preliminary screening: Chemical indicator tubes are allowed only as an initial check; GC must be used for quantitative results.
• Sampling protocol:
  • Samples must be free from interfering contaminants (water vapour, oil aerosol).
  • Sampling under system pressure using a constant flow rate; probe mounted in an extraction tube and measurement carried out at system pressure.
  • Use of membrane holder and stainless steel collection tubes; avoid temperature drops and ensure clean, degreased sampling lines.
• Measurement conditions:
  • Ensure steady state of compressed-air system before measurement; repeat measurements may be required to demonstrate repeatability.
  • Record sampling pressure and temperature; sampling system temperature must be above dew point.
  • Humidity limits: relative humidity should be below about 75% and within equipment limits.
• Reference conditions and corrections:
  • Results are reported at reference conditions (typically 20 °C, 1 bar absolute) or at actual conditions, with a procedure for recalculating concentrations for pressure/temperature differences.
• Uncertainty and reporting:
  • Provide estimates of measurement uncertainty (typically expressed at a confidence level, e.g., 95%).
  • Test report must document system description, sampling point, equipment/materials/calibration, declared oil‑vapour concentration (reference and actual), uncertainties and dates.

Applications and who uses this standard

ISO 8573-5 is used by:

• Quality managers and engineers in industries relying on clean compressed air (pharmaceuticals, food & beverage, electronics, medical devices).
• Compressor and dryer manufacturers, service providers and test laboratories performing compressed-air purity assessments.
• Facilities seeking compliance with ISO 8573‑1 purity classes where oil‑vapour content forms part of total oil classification.

Practical applications include routine air quality monitoring, validation of filtration/separation systems, commissioning, and troubleshooting contamination sources.

Related standards

• ISO 8573‑1 (contaminants and purity classes)
• ISO 8573‑2 (aerosol oil test methods)
• ISO 8573‑3 (humidity test methods)
• ISO 8573‑6 (gaseous contaminants)
• ISO 9486 / ISO 9487 (workplace air GC methods)

Keywords: ISO 8573-5, compressed air, oil vapour, organic solvent content, gas chromatography, sampling, compressed-air purity, test methods, measurement uncertainty.