Overview
ISO 8573-6:2003 - Compressed air: Part 6 - Test methods for gaseous contaminant content defines accepted test methods, sampling techniques, measurement and reporting practices for gaseous contaminants in compressed air. The standard covers measurement and evaluation procedures, uncertainty considerations and reporting for carbon monoxide (CO), carbon dioxide (CO2), sulphur dioxide (SO2), nitric oxide (NO), nitrogen dioxide (NO2) and hydrocarbons C1–C5 (see ISO 8573-5 for C6+). Methods are also applicable to other gases.
Key topics and requirements
- Gases covered: CO, CO2, SO2, NO, NO2, hydrocarbons (C1–C5).
- Sampling techniques:
- Gas sampling bags (e.g., fluoroethylene propylene) - flush bag for 5 minutes before filling; use PTFE tubing and pressure-reducing valve; bring an unused bag to the lab for a blind test.
- On-line sampling at system pressure using stainless-steel probes with pressure-tight valves.
- Gas detector tube sampling (on-site, colorimetric).
- Recommended measurement equipment:
- Nondispersive infrared (NDIR) for CO and CO2 (and SO2 by NDIR or UV‑fluorescence).
- Heated flame ionisation detector (HFID) for hydrocarbons C1–C5.
- Chemiluminescent detector (CLD/HCLD) with NO/NO2 converter for nitrogen oxides.
- On-site gas detector tubes for direct reading.
- Reference conditions: default reporting basis is 20 °C, 0.1 MPa(a), and zero relative water vapour pressure unless otherwise agreed.
- Evaluation & units: results reported as volume fractions (ml/m3 or % by volume); ISO provides preferred units and symbols.
- Uncertainty & quality: guidance on estimating measurement uncertainty and confidence limits (95% typical); consider calibration and measurement system integrity.
- Reporting requirements: reports must describe the compressed air system and conditions, sampling point and method, analytical system and calibration, declared concentration values (with dates and atmospheric conditions) and uncertainty.
Practical applications and users
ISO 8573-6 is essential for organizations that need verified compressed air quality, including:
- Compressor and air treatment manufacturers
- Plant engineers and maintenance teams
- Quality managers in pharmaceuticals, electronics, food & beverage and medical device manufacturing
- Laboratory analysts and third‑party testing services
- Facilities specifying compressed air purity for pneumatic instruments or breathing air
Use cases include baseline air quality assessment, routine monitoring, compliance with purity classes (ISO 8573-1), and validating filtration/drying systems.
Related standards
- ISO 8573-1 (Contaminants and purity classes)
- ISO 8573-5 (Oil vapour and organic solvent content)
- Other ISO 8573 parts for humidity, particles, microbiological content and water.
Keywords: ISO 8573-6:2003, compressed air, gaseous contaminants, test methods, gas sampling bags, on-line sampling, NDIR, HFID, CLD, gas detector tubes, compressed air purity.