Keeping welding fume at bay: Minimizing risks
What is welding fume and where does it come from?
During arc welding, the arc itself reaches temperatures of several thousand degrees. Metal vaporizes, reacts, and condenses to produce welding fume. It is made up of both gaseous elements (such as ozone, carbon monoxide, carbon dioxide, or nitrogen oxides) and particulates, like iron, nickel, and lead oxides, manganese, or chromium (VI) compounds. Yet around 95% of the emissions come from just one source: the filler metal (i.e., the wire that is continuously fed into the weld pool).
Welding fume is largely a hidden danger. As the majority of the particles are ultra-fine (often smaller than 1 µm, some even less than 0.1 µm), they are easily inhaled. Certain particles can even reach the alveoli—the air sacs in the lungs where oxygen and carbon dioxide is exchanged with the blood (Diagram 1). From there, they can (depending on their composition) penetrate into the bloodstream. The consequences can be severe, ranging from chronic respiratory problems (e.g., siderosis with iron oxides) to toxic effects caused by exposure to carbon monoxide, nitrogen oxides, ozone, or manganese oxides. Chromium (VI) compounds and nickel oxide even represent a carcinogenic risk, especially when welding high-alloy steels.
Limit values help, prevention is better
Of course there are regulatory standards that have to be observed. In Austria, a distinction is made between MAK values (maximum workplace concentration) and TRK values (technical reference concentration). While MAK values are considered harmless when adhered to, TRK values do not guarantee any freedom from risk. They are a technical standard value, often for substances whose harmlessness is not assured, such as chromium (VI) compounds. The standard value here is 0.02 mg/m3.
Different countries enforce different emission values. The Netherlands is particularly strict with a respirable fraction of 1 mg/m³, Germany stipulates 1.25 mg/m³, while a value of 5 mg/m³ ambient air applies in Austria (as well as France, Belgium, Norway, USA, and Canada). However, it is important to note that limit values, standards, and regulations are just a snapshot of the situation at a given moment and can change at any time. Companies should regularly check the current national requirements and adapt their risk assessments accordingly.
The systematic approach: the STOP principle
Effectively reducing welding fume follows a clear hierarchy: the STOP principle. Substitution and technical solutions act as collective protection and thus also protect people in the vicinity—these are therefore the measures that should be prioritized. If this is not possible, companies should adopt organizational measures that mainly limit residual exposure. The final measure is personal protective equipment (PPE). As PPE only protects an individual, it is considered the lowest rung of the STOP hierarchy.
S - Substitution: Lower-emission processes (e.g., TIG), alternative welding wires and shielding gases, optimized arc length (Diagram 2)
T - Technical measures: Fume extraction torches, automated cells, extraction hoods
O - Organizational measures: Residue-free components, clean and well-structured workplaces, reduced exposure time, exclusion of non-essential personnel, regular training
P - Personal measures: Respiratory protection if all previous measures are not sufficient
An effective lever lies in the hands of those who weld daily:
When the arc makes the difference
A study conducted by a German research and joining technology association (FEF) together with Fronius demonstrated just how important the correct welding machine settings are in reducing welding fume emissions. In addition to the process itself, the parameters have a significant impact on the fume emission rate (FER).
In a comparison of three different process variants (standard, low spatter control (LSC), and pulsed arc), the pulsed arc proved to be the process that produced the most stable material transfer and the lowest emission rate. Process parameters such as wire speed, voltage, and amperage were the same in each case.
Welding was carried out with a G-3Si1 wire (Ø 1.2 mm) on hot-rolled unalloyed structural steel (S235JR) with the shielding gas M21 (82% Ar/18% CO2), fully mechanized and under reproducible conditions.
What the measurements revealed
Surfacing beads:
When welding with a fume extraction torch, particularly low FER values were found at a wire speed of 5 m/min and with a neutral torch position. Surprisingly, the FER was lower at 11 m/min than at 8 m/min (Figure 1). This was due to a greater number of short circuits at 8 m/min, which in turn led to increased emissions. A constant factor across all tests was that a pull technique slightly reduced emissions at all wire speeds.
However, it was the arc length correction that had the greatest impact. Even a moderate increase in the average voltage (by around +0.4 V) significantly reduced the FER at all wire speeds (Figure 2). As an optimal arc length minimizes short-circuit phenomena, a smoother material transfer can be ensured—resulting in less metal vapor and fume.
Fillet welds:
Here, emissions were lower overall, but showed the same behavior (Figure 3):
- 5 m/min wire speed: approx. 0.55 mg/s
- 8 m/min wire speed: approx. 0.7 mg/s
- 11 m/min wire speed: approx. 1.7 mg/s
Here, too, the pull technique proved to be advantageous when welding with a fume extraction torch, especially at high wire speeds. A detailed test at 11 m/min resulted in an FER minimum at a correction of -1.5 volts. If the arc was extended or shortened, the emissions increased again—either due to a higher process power or an increased number of short circuits.
Rules for the workshop
The process is key: The pulse process provides a particularly favorable material transfer in many applications.
Precisely adjust the arc length: The arc should be kept as short as possible so that the process operates with a low but stable short-circuit frequency.
Optimize the wire speed: A wire speed of 5 m/min produced the lowest emission values under test conditions. As a rule of thumb, a lower arc power reduces emissions even if the welding process remains the same.
Capture fumes before they spread
In addition to the welding process and machine parameters, capturing welding fume emissions is critical. Fume extraction torches like the Fronius MTW 500i Exento capture welding fume right at the source: the weld pool. When used in conjunction with a powerful mobile Fronius Exento HighVac extraction system, up to 99% of all fumes can be effectively captured. However, it is important to note that the volumetric flow rate of the torch extraction system must be kept within the optimum range. An insufficient flow rate reduces performance, while an excessive rate can break the protective gas shield and cause spatter or seam irregularities. Regular testing with a suitable measuring tool is recommended.
Wherever a fume extraction torch cannot be used (such as during MMA welding), the mobile Exento LowVac extraction system is an effective alternative. Not only does its flow-optimized and rotatable extraction hood cover a large area, but its large filter area and mobility make it ideal for frequently changing workplaces.
All Exento systems meet the requirements of DIN EN ISO 21904-1 for capturing and separating welding fume. This standard specifies the general requirements for local fume capture and extraction equipment, including the design of hoods, ducting, filter units, airflow rate systems, warning systems, and safety-related workplace instructions. Its purpose is to ensure that welding fume is captured as completely and as closely to the point of origin as possible and reliably separated.
Personal protective equipment: welding helmets with fan filter unit
Personal protective equipment is used to protect individual welders when area-based extraction systems reach their limits. Powered air purifying respirators (PAPR) reliably protect against the finest welding fume particles by continuously forcing filtered, clean air into the helmet.
The combination of positive pressure in the helmet and highly effective particle filters significantly reduces the level of pollutants, especially when working in confined spaces, hard-to-reach areas, or with processes lacking direct extraction at source. Modern Fronius Vizor Air welding helmets with a fan filter unit are a perfect example of effective PPE. A uniform air flow, reduced heat load, and an unobstructed field of vision support precise work even during long shifts.
Conclusion: welding fume exposure is not inevitable
Welding fume can be controlled. With the right combination of modern process control, parametric fine adjustment, pinpoint extraction, and personal protective equipment, the workplace is not only safer but the profession becomes more productive and attractive as a result. Or put another way, the fume emission rate is not a law of nature. It is an adjustable variable and welding specialists already have the tools at their disposal to bring it firmly under control.
More about welder safety: https://www.fronius.com/en/welding-technology/world-of-welding/welding-safety