The welding fume separation class W3 - new ISO 21904 features

The international standard for the testing of welding fume filtering devices describes the requirements placed on devices with regard to operability, detection and separation efficiency. For high-alloy steels, this standard requires a separation efficiency against welding fumes of at least 99%: Welding fume separation class W3. In Germany, air filtered with appropriately tested and certified equipment may also be returned to the work area when processing high-alloy stainless steels. In other countries, the W3 certificate, which is awarded by the Institute for Occupational Health and Safety (IFA) in Sankt Augustin, is regarded as a sign of quality.

Until mid-2020, the basis for this audit was the ISO 15012 series of standards. It was fundamentally revised and reorganised under the number ISO 21904. The new series of standards was published in June 2020. Since then, the IFA has been conducting tests according to the German edition of the DIN EN ISO 21904 standard. Existing certificates according to DIN EN ISO 15012 remain valid until the respective expiry date and continue to allow the operation of the units with clean air recirculation in Germany.

Depending on the type and size of the collection device (e.g. extraction bonnet or extraction burner), certain air velocities are prescribed in the suction field. This results in minimum volume flows, which have been specified for the first time in the new ISO 21904 standard, also for welding torches with integrated extraction.

A smooth-running and easy-to-position extraction arm is a safety aspect. If the extraction arm is sluggish, it will be adjusted less frequently and welding fumes will not be collected. Therefore, the new ISO 21904 standard also regulates the force required to move extraction arms.

Another important point in the revision results from the scope. The ISO 21904 standard only applies to extraction systems. These require the presence of a detection device, for example an extraction bonnet. Such detection devices are not present in room ventilation systems such as filter towers or when the room air is drawn in via a pipe with ventilation grilles. For this reason, room ventilation systems no longer receive a W3 certificate. However, the same applies here: Existing DIN EN ISO 15012 certificates retain their validity until they expire, but can no longer be renewed thereafter.

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