Dust and Fume Extraction for MIG, Stick and Flux-Cored Welding

• Metal Inert Gas (MIG)/Gas Metal Arc Welding (GMAW): MIG welding uses a consumable metal wire fed from a spool, which acts as both the electrode and the filler metal. A shielding gas is used to protect the weld seam from oxidation. MIG welding is a versatile and relatively simple welding process that is easy for beginners to learn. It is a popular form of welding for many general fabrication shops and other applications. A related type of welding, Metal Active Gas (MAG), uses non-inert shielding gasses that react with the filler metal. 
• Stick/Shielded Metal Arc Welding (SMAW): Stick welding is similar to MIG welding, but uses a consumable stick or rod instead of the welding wire. The rod is covered with a protective coating, which vaporizes to create its own shielding gas. Stick welding is popular for construction, maintenance and repair applications because it is highly portable and suitable for outdoor use. 
• Flux-Cored Arc Welding (FCAW): FCAW welding uses a continuous wire as the welding consumable, similar to MIG or MAG welding. The weld wire used for FCAW welding is hollow and filled with a fluxing material. When heated, the flux core melts into a protective slag coating on top of the weld seam and produces shielding gasses. Sometimes, an external shielding gas mixture is used in addition to the flux core; this is known as “dual shield” welding and is commonly used for structural steel. Flux-cored welding can be performed outside in a variety of conditions and produces a very strong bond, making it ideal for heavy-duty applications.
• Tungsten Inert Gas (TIG)/Gas Tungsten Arc Welding (GTAW): TIG welding uses a tungsten electrode to create the arc. Unlike softer metals used in MIG or stick welding, tungsten does not burn off. In fusion welding, no filler materials are used; the high heat created by the tungsten arc fuses the materials together. However, TIG welding commonly uses a filler rod, which is fed by hand into the weld seam. Filler rods are available in various sizes and compositions for welding different base materials.

• Weld fumes from welding mild steel may contain fluoride, manganese, silicon, titanium and sodium and potassium silicates. 
• Weld fumes from welding aluminum often contain fluorine, arsenic, copper, silicon and beryllium. 
• Welding iron metals may produce weld fumes containing manganese, silicate, and various organic binders. 
• Welding stainless steel produces dangerous hexavalent chromium in addition to the elements commonly found in fumes from mild steel. 
• Welding galvanized steel produces zinc oxides. 
• Sodium and other fluorides are commonly used as the flux in FCAW welding; these elements end up in the weld fume.

Weld fumes from arc welding are dangerous because the high heat of the welding process produces very tiny particulates (~01 – 0.5 microns) that can be inhaled deeply into the lungs and can even make their way into the bloodstream and to other body systems. Risks associated with weld fumes depend on the exact composition of the fume and the level of exposure. Potential health risks of weld fumes include: 

• Cancer of the lung, larynx and urinary tract. 
• Manganism, a neurological disorder with symptoms similar to Parkinson’s Disease. 
• Kidney damage. 
• Stomach ulcers. 
• Lung damage including chronic bronchitis, chronic obstructive pulmonary disease (COPD), or pulmonary fibrosis.

These are PELs for some of the elements and compounds commonly found in weld fumes: 

• Zinc oxide: 5.0 mg/m3 (for zinc oxide fume or respirable dust) 
• Lead: 50 μg/m3 (PEL)/action limit 30 μg/m3
• Hexavalent chromium: 5 μg /m3
• Nickel: 1.0 mg/m3
• Cadmium: 0.005 mg/m3
• Manganese: 5.0 mg/m3
• Cobalt: 0.1 mg/m3

In addition, manufacturers may need to follow OSHA regulations and NFPA standards for combustible dust. Weld fumes may be combustible under certain conditions; manufacturers who do not know the Kst value of their weld fume should consider testing. Combustible dusts are regulated under OSHA’s General Duty Clause (Section 5(a)(1)) with additional requirements under the Hazardous Locations (§1910.307), Hazard Communication (§1910.1200) and Housekeeping (§1910.22) standards. In addition, manufacturers dealing with combustible dusts must follow National Fire Protection Association (NFPA) standards for the prevention of fires and explosions.

Source capture is preferred for both robotic and manual welding applications. Read more: Which capture method is best for weld fumes? 

• Manual welding fumes can be captured using a fume arm, backdraft or sidedraft table, or a fume gun. The source capture solution should be designed to pull welding fumes away from the welder’s breathing zone. Manual welding almost always requires a source capture solution to prevent the welder from breathing in toxic welding emissions; PPE is not a suitable substitute for implementing effective engineering controls. 
• Robotic welding applications can often be kept under a hood or enclosure. The hood keeps weld fumes contained for efficient source capture. If the application can’t be enclosed (for example, if overhead cranes and lifts are used), an ambient air filtration system may be used.  Ambient systems are best used when humans are not working in the area where robotic welding is taking place, such as an automated production line. The system must be designed to keep weld fumes from propagating into areas where humans are working. For some applications, the robot arm can be fitted with a close-fitting hood (such as RoboVent FlexTrac) for collection of weld fumes as they are created. 
• Multiple robotic weld cells or manual welding stations can be ducted to a large centralized dust collector (which may be located inside or outside the facility). Alternatively, smaller collectors may be used to capture weld fume from a single weld cell or station. Small portable units or integrated units such as the Ventboss series can be great to support individual manual welders.
• Depending on the volume and combustibility of fumes collected by arc welding, the dust collector may need to be equipped with a deflagration system. This system may include explosion vents for safe venting of the energy from a dust collector explosion, isolation valves and a rotary airlock to prevent dust in the collection bin from being used to fuel an explosion.