Harmful substances are rarely generated right where a fixed extraction system is installed. Welding work is performed in different locations. Grinding work is done directly on the component, not on a fixed table. Maintenance is performed right where the machine is located at that moment.
Mobile filtration systems solve exactly this problem: portable extraction systems that operate without a permanent installation, capturing harmful substances directly at the source and returning the purified air to the workshop. Plug and Play — connect, turn on, and get to work.
The two most common applications in metalworking are welding fumes and grinding dust. Both have very different technical requirements. Understanding this helps you choose the right equipment.
When is a portable system preferable to a fixed one?
A fixed system is cost-effective if the same harmful substances are consistently generated at a specific workstation—for example, a welding station operated in shifts. Mobile units are the best choice if the source of the harmful substances varies, the workstation is used infrequently, no structural modifications are possible, or there is a short-term shortage of capacity.
In practice, many companies use a combination of both solutions: fixed extraction systems at fixed workstations, and mobile units for variable tasks, service calls, or special situations.
Mobile welding fume extraction: filtration class and technology
Welding fumes contain extremely fine particles that penetrate deep into the respiratory tract. In high-alloy steels with chromium and nickel contents exceeding 5%, carcinogenic CMR substances are formed. For these, filtration class W3 applies in accordance with DIN EN ISO 21904-1, which is mandatory in Germany under TRGS 528.
For standard welding work on non-alloy steels, Class W2 is sufficient. Those who regularly work with different materials or do not wish to perform a separate assessment for each job should opt for a W3-certified device from the outset.
The downward flow principle protects the weld bead
Professional mobile welding fume extractors operate on the downward flow principle: contaminated air is drawn in from the top into the chamber, purified through the filter cartridge, and released back into the environment from the bottom of the unit. This offers a practical advantage that is often overlooked.
Excessive suction directly at the welding point can draw shielding gas away from the weld zone and cool the weld itself—both of these factors cause quality issues in the workpiece. The downward flow principle, with a properly adjusted extraction arm, effectively captures welding fumes without interfering with the process. Ideally, the extraction hood should be positioned no more than 20–30 centimeters from the weld spot.
Filter media for welding fumes
For standard welding applications, a cellulose cartridge (M-CEL) is the most cost-effective solution: large filter surface area, good separation efficiency, and easy replacement. For W3 requirements regarding CMR substances, a polyester filter cartridge with a PTFE membrane of filtration class H13 is required: maximum separation efficiency, suitable for carcinogenic welding fumes, safe filter replacement thanks to the low adhesion of separated dust. As an option, an activated carbon insert can be added to absorb gaseous odorous substances—useful when multiple units are in use in enclosed areas of the workshop.
Mobile extraction of sanding dust: sparks as an underestimated hazard
Sanding processes generate hot metal particles. This is precisely what makes the extraction of sanding dust technically more complex than other types of dust extraction—and explains why a standard filter unit is not suitable for this application.
If glowing particles come into direct contact with a filter cartridge, the filter material can catch fire from the inside. The fire is initially invisible. In the worst-case scenario, the entire unit or the surrounding area could catch fire.
Spark-extinguishing system as a first-stage separator
Professional mobile vacuum cleaners for sanding dust feature a built-in stainless steel water tank that acts as a spark pre-separator. The air drawn in first comes into contact with the water’s surface: glowing particles are cooled and extinguished, while coarse dust settles out. Only then does the air reach the filter cartridges.
At the same time, in the upstream settling chamber, coarse sanding dust settles by gravity before reaching the filter chamber. This protects the filter cartridges and extends their service life. The water level in the tank must be checked regularly using the visual level indicator: an empty tank renders the spark protection completely ineffective.
Automatic cleaning with compressed air
Under heavy dust loads, filter cartridges become clogged quickly. Without cleaning, the pressure drop across the filter increases, the vacuum decreases, and suction capacity is measurably reduced. The Jet versions of professional sanding dust extractors clean the cartridges automatically and cyclically using compressed air pulses—during operation, without interrupting work. This significantly extends the filter’s service life and maintains a constant airflow rate throughout the entire shift.
Equipment without automatic cleaning is the most suitable and cost-effective option for low dust levels or locations without a compressed air supply.
Filter media and ATEX
The polyester filter cartridge (M-PES) is the standard solution for most sanding applications in metalworking. For applications requiring higher separation efficiency, a PTFE-coated version (M-PES/TF) is available. For areas with flammable dusts, the flame-retardant version (M-PES/FR) is used. For ATEX applications involving explosive dusts such as aluminum or magnesium, an antistatic, certified filter cartridge (M-PES/AX/EXAM ACCREDITED) is required—in this case, both the device and the filter media must be certified in accordance with the ATEX Directive 2014/34/EU.
Overview of Selection Criteria
- Airflow rate: For a single welding station equipped with an extraction arm, typical mobile units have an airflow rate of between 1,000 and 1,400 m³/h. For two simultaneous workstations or for large-scale grinding applications with multiple extraction points, the required airflow rate increases accordingly. If the airflow rate is too low, harmful substances will escape from the extraction zone.
- Filter class and filter media: W3 with H13 cartridge for CMR welding fumes; class M as the minimum requirement for dusts harmful to health. The filter media depends on the material, the fire risk, and ATEX requirements.
- Spark protection: When performing grinding operations that generate sparks, the integrated water pre-separator is not an optional feature, but a fundamental requirement for safe operation.
- Noise level: Typical units operate at between 72 and 74.5 dB(A). With the optional sound-absorbing hood, noise levels can be reduced to between 65 and 71 dB(A)—an important consideration when multiple units are operating in the same area of the warehouse.
- Maintenance: The horizontally mounted filter cartridges allow for quick replacement without tools or specialized personnel. An operating hour counter provides approximate readings; an optional differential pressure gauge provides precise information on the actual load status.
The right tool for the right job
Mobile filtration systems are not a compromise: they address a different problem than stationary systems. For welding fume extraction, the filtration class is the most critical factor: W3 with a PTFE membrane filter for CMR substances, and W2 for standard applications. For sanding dust extraction, the integrated spark pre-separator is the key design feature—a unit without a water tank is not suitable for this application.
When selected properly, equipped with the appropriate filter media, and maintained regularly, portable units offer the same level of protection as fixed systems—and significantly greater flexibility.
Frequently Asked Questions About Mobile Filtration Systems
What filter class do I need for a portable welding fume extraction system?
It depends on the base material. For unalloyed structural steels, Class W2 is sufficient. For high-alloy steels with a nickel or chromium content exceeding 5%—particularly stainless steel—the TRGS 528 standard requires Class W3 with an H13 filter cartridge. In case of doubt, the risk assessment provides the necessary information.
What is the difference between Grindex DF and Grindex DF Jet?
Both series of units are designed for grinding dust that produces sparks and feature a water tray and three-stage filtration. The difference: the Jet versions automatically and periodically clean the filter cartridges with compressed air during operation. This significantly extends the filter’s service life. The non-Jet DF versions are suitable for lower dust volumes or locations without a compressed air connection.
When should a W3 filter cartridge be used instead of a standard M cartridge?
This also applies when welding fumes contain CMR substances, specifically when welding high-alloy steels with a nickel and chromium content exceeding 5% and certain filler materials. A standard cellulose filter cartridge is not approved for use with CMR substances.
What does ATEX mean in the context of mobile extraction systems?
ATEX refers to European Directive 2014/34/EU for equipment used in potentially explosive atmospheres. In the presence of flammable or explosive dusts such as aluminum or magnesium, both the equipment and the filter media must be certified. The required equipment category is determined by the zoning of the work area.
How often should the filter be replaced?
It depends on the type of dust and the filter’s loading. The operating hour counter provides approximate values. An optional differential pressure gauge is more accurate: if the pressure drop exceeds the maximum permitted value, the filter is clogged and must be replaced, regardless of the number of operating hours.