Overview
ISO 21904-2:2020 specifies a standardized laboratory method to test and mark the separation efficiency of welding fume capture and separation equipment. The standard defines how to charge equipment with welding fume, measure incoming and outgoing fume concentrations, and calculate separation efficiency under defined conditions. It applies to capture/separation units manufactured after publication and excludes testing of filter cartridges independent of the host equipment and general ventilation systems covered by ISO 21904-1.
Key topics and technical requirements
- Scope and applicability: Test method for welding fume separation equipment (including modular systems and free‑standing units); excludes standalone filter cartridge testing.
- Test arrangements: Two main setups - a test cabin (enclosure) for most units and a direct ducted‑outlet arrangement for equipment with ducted outlets.
- Welding fume source: Must be able to maintain an emission rate (example target in the document) to reliably charge the unit; emission rate measurement follows ISO 15011-1.
- Preconditioning and test duration: Equipment is typically charged for 30 minutes prior to measurement; for non‑cleanable filters a subsequent 30‑minute measurement is used; cleanable filters require additional cycles and averaging.
- Measurement parameters:
- Incoming and exhausted welding fume concentrations are sampled and compared.
- Air volume flow rate must be measured during the test (measurement capability up to 2 000 m3/h with ±10% accuracy is specified).
- Emission rate, flow rate and test time are used to compute incoming concentration.
- Procedures by equipment type: Specific measurement sequences for units without filter cleaning, units with manual or automatic cleaning, and units using electrostatic precipitators.
- Calculation and statistics: Separation efficiency is calculated from measured concentrations. Two test runs are required; results are evaluated using ISO 2602 to produce the average, the 95% one‑sided confidence interval and the lower confidence limit. If the lower confidence limit falls below the required efficiency, design improvement is advised.
- Reporting and accuracy: Requirements for test reports and accuracy of measurement are specified; annexes provide test cabin and welding source examples.
Applications and users
ISO 21904-2 is intended for:
- Manufacturers of fume extractors, local exhaust ventilation (LEV) units, filter modules and electrostatic precipitators who need to validate and mark separation efficiency.
- Independent test laboratories performing performance verification and certification.
- Occupational health & safety professionals, plant engineers and procurement teams selecting capture and separation equipment for welding shops and fabrication facilities.
- Regulators and conformity assessors checking claims about fume recirculation and exhaust safety.
Keywords: ISO 21904-2, welding fume separation efficiency, welding fume testing, fume capture equipment, LEV testing, filter cleaning, electrostatic precipitator testing.
Related standards
- ISO 21904-1 - General requirements for equipment for capture and separation of welding fume.
- ISO 15011-1 - Laboratory method for sampling fume and gases; determination of fume emission rate.
- ISO 2602 - Statistical interpretation of test results (confidence intervals).
- References to EN 1093‑6 and EN 1093‑7 are also cited as methodological bases.