Overview
ISO 8573-5:2025 - "Compressed air - Contaminant measurement - Part 5: Oil vapour content" specifies a quantitative test method for determining oil vapour content in compressed air. The standard uses pressurized sampling onto sorbent tubes followed by thermal desorption and gas chromatography (GC) to measure gaseous hydrocarbons (VOC/SVOC). It defines sampling, measurement, evaluation, uncertainty treatment and reporting so the measured result can be used to state the compressed air purity class for oil in accordance with ISO 8573-1.
Key topics and technical requirements
- Scope & purpose: Measurement of oil vapour (sum of gaseous hydrocarbons from n‑hexane to higher boiling SVOCs) for assessing compressed air purity classes (class 0,1,2,3,4,X).
- Sampling method: Pressurized sampling through a sorbent tube; materials in the sampling train must not alter sample composition. Record temperature, pressure, pressure dew point and flow. Sampling temperature must exceed pressure dew point to avoid condensation.
- Sample conditioning: Upstream aerosol filter (glass microfiber disc) to remove oil aerosols before sorbent tube.
- Analytical technique: Thermal desorption of sorbent tubes into a GC with non‑polar capillary column (e.g., methyl siloxane) and detection by FID or MS. Quantification generally uses toluene response factor; if SVOCs (> n‑C16) contribute >10% of chromatographic area, calibrate additionally with n‑C16.
- Calibration & quality control: Requirements for calibration standards, dilution solvent and blanks (laboratory and field blanks). Annexes provide an example test report and indicative preliminary methods.
- Uncertainty & reporting: Procedures for calculating mass/concentration, uncertainty estimation, repeatability and required elements for the test report.
- Modernization: Introduction of thermal desorption (avoiding solvent use) and reusable standardized adsorbents compared to the 2001 edition.
Applications and who uses it
- Verifying compressed air purity for critical industries: pharmaceutical, food & beverage, electronics, medical device manufacturing.
- Specifying and validating compressed air treatment (filters, dryers, oil removal systems).
- Routine compliance testing, acceptance testing in supply contracts, environmental monitoring and troubleshooting oil contamination in pneumatic systems.
- Typical users: testing laboratories, compressor and air treatment manufacturers, quality managers, maintenance engineers, consultants and regulatory or procurement teams.
Related standards
- ISO 8573-1 - Compressed air - Contaminants and purity classes (defines oil purity classes)
- ISO 8573-2 - Measurement of liquid oil and aerosols
- ISO 8573-6 and ISO 16000-6 - Guidance and methods for other organic/gaseous contaminants and VOC sampling/analysis
Keywords: ISO 8573-5:2025, compressed air, oil vapour content, gas chromatography, thermal desorption, sorbent tube sampling, compressed air purity.
