Welding fume extraction is an important aspect in industrial manufacturing to control air quality and protect the health of employees. Welding fume class W3 is of particular importance. What is meant by this and who needs a welding fume extraction system with W3 certification?
W3 certification as a seal of quality
The W3 certification is a certification of the Institute for Occupational Safety of the German Social Accident Insurance (IFA) and an important quality feature for welding fume extraction units.
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Units with W3 certification may also be used in Germany for processing high-alloy steels. The certificate confirms that the separation efficiency of the welding fume extraction unit has been tested using high-alloy steel and that the filter system filters 99 percent of all pollutants out of the air. The W3 certification is recognised worldwide and is an important component of occupational health and safety.
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This certification gives the user of a welding fume extraction system permission to recirculate the cleaned air. This means that in countries such as Germany, for example, W3-certified welding fume extraction units in accordance with TRGS 528 can be used to safely recirculate the filtered exhaust air back into the working environment. This is also easy on the wallet and the environment, as heated hall air does not have to be discharged to the outside, especially in the cold winter months.
Differentiation of the welding fume classes W1, W2 and W3
The welding fume classes W1, W2 and W3 differ in the separation rates of the carcinogenic pollutants. Class W1 has the lowest separation efficiency, while class W3 has the highest percentage separation efficiency. Filters of separation class W1 are suitable for unalloyed steels or low-alloy steels. Class W2 has a separation efficiency of more than 98 percent and is suitable for welding alloyed steels with nickel and chromium contents (5 to 30 percent). Welding fume class W3 confirms that the filter system filters all toxic substances out of the air to 99 percent and is suitable for welding high-alloy steels with nickel and chromium components with proportions above 30 percent.
| Filter class |
Seperation (%) |
Application |
| W1 | ≥ 95 | Non-alloyed steel, alloyed steel with alloy components e.g. Ni and Cr, low-alloyed steel, x ≤ 5 % |
| W2 | ≥ 98 | Same as W1, plus alloyed steel with alloy components e.g. Ni und Cr (5 % ≤ x ≤ 30 %) |
| W3 | ≥ 99 | Same as W2, plus alloyed steel with alloy components e.g. Ni and Cr (highly alloyed steel with x ≥ 30 % Ni-based alloys) |
Relationship between welding fume class W3 and W3 certification
Welding fume class W3 and W3 certification refer to the same concept, namely the extraction of welding fumes, but they refer to different aspects of it.
Welding fume class W3 refers to the separation efficiency of welding fume filters on high-alloy steels and confirms that the filter system filters all toxic substances out of the air by 99%. W3 approval refers to the approval of equipment suitable for the separation of welding fumes. As already mentioned, a W3 approval allows the cleaned air to be returned to the workspace and is issued by the Institute for Occupational Safety and Health (IFA).
In summary, welding fume class W3 is a classification system for welding fume filters that describes the degree of separation of carcinogenic pollutants. W3 certification is a certification from the IFA that confirms that a filter unit filters all pollutants out of the air by 99%. Units with W3 certification may also be used in Germany for processing high-alloy stainless steels and are an important quality feature for welding fume filter units.
What types of welding work require the use of W3-certified extraction units?
In Germany, the vapours generated during the welding of high-alloy steels must be extracted and filtered using W3-certified fume extraction units. The purified exhaust air may be returned to the work area in accordance with TRGS 528. Hexavalent chromium in particular (usually called chromium (VI)) is very harmful.
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It is found in all types of stainless steel and, according to extensive scientific studies, is a known cause of cancer. Therefore, it is imperative to use an extraction system with a W3-certified filter that can remove these harmful particles when the chromium-nickel content is above 30%.
A W3 class welding fume extraction system is also suitable for extracting welding fumes from unalloyed steels and precious metals, galvanised materials and aluminium in heavy-duty applications.
What requirements must extraction systems fulfil in order to obtain the W3 certificate?
In order to obtain the W3 certificate, extraction systems must meet certain requirements. These requirements are described in the standard DIN EN ISO 21904-1.
ISO 21904 is an international standard that describes the requirements for welding fume filter units. The standard was restructured in June 2020 and incorporated into the DIN EN ISO 21904 "Occupational health and safety in welding" series of standards. The innovations of ISO 21904 concern the requirements for operability, detection and separation efficiency of devices used for welding fume separation.
With the W3 certificate, the testing body awards a seal of quality to equipment that meets the highest requirements. The extraction units must meet the requirements in terms of operability, collection and separation efficiency. The certificate also permits the operation of the extraction system during the welding of stainless steels (chrome-nickel steels) in recirculation mode.
How often should filters in a welding fume unit be changed?
There is no universal answer to the question of how often filters in welding fume extraction units should be changed, as this depends on various factors such as the type of welding work, the frequency of use and the size of the filters. However, it is important to check and maintain the filters regularly to ensure that they are working properly and extracting welding fumes effectively. Some welding fume units have an automatic filter cleaning function that cleans the filter without the need to replace it. It is advisable to contact the extraction unit manufacturer for filter replacement recommendations and to ensure that the fume extraction unit is properly maintained.
For more information on welding fume filters, see our blog article: What you should consider with welding fume filters
Do you have any further questions on the subject of W3 welding fume extraction or are you looking for a reliable extraction unit with W3 certification?
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