Overview
ISO 10397:1993 specifies a standardized fibre count method for assessing asbestos emissions from stationary sources (ducts, chimneys, flues). The method uses isokinetic sampling to withdraw a known volume of gas through a filter, makes the filter transparent, and counts fibres by phase-contrast optical microscopy. It is intended to quantify fibre concentrations and to evaluate the effectiveness of dust- and fibre-collection equipment at asbestos works or other processes handling fibrous materials.
Key topics and technical requirements
- Isokinetic sampling: withdraw gas at a rate matching the duct gas velocity so sampled particles represent the flow. The standard covers nozzle size, sampling rate, and validation of isokinetic conditions.
- Sampling train and apparatus: probe with nozzle and fibre collector, pump (fan/vacuum), flow and temperature measurement (Pitot-static tube referenced), and filters with known effective filtering area.
- Filter treatment and analysis: procedures to clear the membrane filter and view it under a phase-contrast optical microscope for fibre counting; analytical technique follows ISO 8672.
- Definition of fibres: the standard defines “regulated” fibres by size and aspect ratio (see clause 3.9) to be included in counts.
- Calculation and presentation: formulas for gas velocity, sampled air volume, validation of isokinetic sampling, and fibre concentration calculations; guidance on presenting and interpreting results.
- Accuracy and limitations: notes that analytical (counting) accuracy strongly affects overall method accuracy; small sampling durations can be sensitive to process fluctuations.
- Health & safety: requirements to assess hazards (asbestos exposure, working at heights, hot/pressurized gases) and to follow site safety procedures.
Practical applications
- Compliance monitoring: measuring asbestos fibre concentrations in emissions to verify regulatory limits or permit conditions.
- Performance testing: assessing efficiency of baghouses, filters, precipitators, and other dust/fibre arrestment systems at asbestos-processing plants.
- Process control and troubleshooting: identifying emission spikes and locating ineffective capture points.
- Environmental and occupational hygiene investigations: provides quantitative data for exposure assessments at plant exhaust points (not for workplace personal sampling).
Who uses this standard
- Environmental compliance officers and regulators monitoring stationary source emissions
- Industrial hygienists and air quality consultants
- Laboratory analysts trained in microscopic fibre counting
- Plant engineers evaluating and commissioning dust/fibre control equipment
Related standards
- ISO 8672 - fibre counting by phase-contrast optical microscopy
- ISO 10312 - fibre identification (electron microscopy) when identification of asbestos vs. non‑asbestos fibres is required
- ISO 3966, ISO 9096 - flow measurement and mass-concentration methods referenced for duct velocity and mass flow calculations
Keywords: ISO 10397, asbestos emissions, fibre count measurement, isokinetic sampling, phase-contrast optical microscope, stationary source emissions, duct sampling, air quality.