Overview
ISO 8760:1990 specifies a short-term, direct-indication method for determining the mass concentration of carbon monoxide (CO) in workplace air using detector tubes. The procedure is intended for concentrations greater than 10 mg/m3 and is suitable for both personal (breathing‑zone) and general area sampling. The standard describes reagents, sampling procedure, performance characteristics and when to prefer more precise chemical or instrumental methods.
Key topics and technical requirements
- Detector tube chemistry: Two common reagent systems are covered - iodine pentoxide (white → green‑brown stain) and potassium palladosulfite (yellow → brown stain).
- Interferents: Lists substances that affect readings (e.g., acetylene, aliphatic and halogenated hydrocarbons; carbon disulfide, halogens, mercaptans, phosphine, phosgene; acetylene and H2S can produce black stains). Some interferents can be removed by pretreatment sections.
- Sampling apparatus: Use manufacturer‑matched detector tube and detector‑tube pump (hand or battery‑operated). Pump volume per stroke must be within ±5% of nominal; test for leaks and flow blockages before use.
- Sampling procedure: Break tube ends, insert tightly into pump, perform prescribed number of strokes, flush pump after sampling, compare stained tube against an unused tube on white background for reading.
- Calibration and correction: Calibration data should be supplied by the manufacturer. Correction factors for pressure, temperature and relative humidity (and known interferents) must be applied when necessary. Recalibration by users is permitted only with trained personnel and controlled gas mixtures.
- Precision & limits: Detector‑tube measurements have larger relative errors at lower concentrations; maximum permissible random error is stated (for example, ±25% at 60 mg/m3). The method is optimized for quick screening rather than high‑precision quantification.
- Safety & disposal: Follow manufacturer guidance and local regulations for disposal of tubes containing toxic or corrosive reagents.
Applications and users
ISO 8760:1990 is practical for:
- Occupational hygienists and industrial safety professionals conducting quick workplace CO exposure checks
- Field technicians performing short‑term, on‑site breathing‑zone monitoring
- Environmental health officers doing rapid area screening where immediate results are needed
Use this standard when rapid, portable CO assessment is required; for regulatory compliance, long‑term monitoring or situations needing high accuracy or interference‑free results, use classical chemical or instrumental methods.
Related standards
- ISO 6879 (performance characteristics for air quality measuring methods) is referenced for performance concepts and calibration practices.
- Manufacturer calibration documentation and applicable national occupational exposure standards should be consulted when applying ISO 8760:1990.