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