The Definition of Welding Fume

Definition of Welding Fume

Welding fume is the cloud of very fine particles and gases created when metal is heated during welding, cutting and similar processes. Metal from the base material, filler wire or rod and coatings vaporizes in the heat of the arc or flame, then cools and condenses into particles small enough to reach deep into the lungs. The fume also carries gases such as ozone, nitrogen oxides and carbon monoxide.

The makeup of the fume depends on the process, the metals, the consumables and any coatings or contaminants on the surface. Mild steel fume is mostly iron oxide with manganese. Stainless steel fume contains chromium, including hexavalent chromium, and nickel. Galvanized steel releases zinc oxide, and old painted or plated metals can release lead or cadmium.

In 2017, the International Agency for Research on Cancer (IARC) classified welding fumes as carcinogenic to humans (Group 1), based on evidence of lung cancer. That finding applies to fume from mild steel as well as stainless.

Health Effects of Welding Fume

• Short-term: irritation of the eyes, nose and throat, coughing, and flu-like symptoms known as metal fume fever, usually after welding galvanized metal.
• Lung disease: bronchitis, reduced lung function, siderosis from iron oxide deposits, and an increased risk of pneumonia.
• Cancer: lung cancer, with additional risk from hexavalent chromium and nickel in stainless steel fume.
• Nervous system: long-term manganese exposure can cause manganism, a condition with symptoms similar to Parkinson's disease.
• Gases: ozone and nitrogen oxides can damage the lungs. In confined spaces, carbon monoxide and shielding gases can build up, and shielding gases such as argon can displace oxygen and act as an asphyxiant.

Regulations

OSHA's welding, cutting and brazing rules are in 29 CFR 1910 Subpart Q for general industry and 1926 Subpart J for construction, including ventilation requirements in 1910.252(c). Individual fume components have their own exposure limits, such as manganese, iron oxide, zinc oxide and lead. Hexavalent chromium has a dedicated standard, 29 CFR 1910.1026, with a permissible exposure limit of 5 micrograms per cubic meter as an 8-hour time-weighted average. In Great Britain, HSE strengthened its position in 2019, stating that general ventilation alone does not adequately control fume from indoor welding and that suitable engineering controls, usually local exhaust ventilation, are needed regardless of how long the welding lasts.

Controlling Welding Fume

Controls should follow the hierarchy of controls:

• Change the process: where possible, choose lower-fume processes and consumables. Stick and flux-cored welding generally produce more fume than MIG or TIG welding.
• Clean surfaces first: remove paint, coatings and oil from the weld area before welding.
• Local exhaust ventilation: use on-torch extraction or a movable hood placed close to the arc. These engineering controls capture fume before it reaches the welder's breathing zone.
• Work practices: keep the head out of the plume and position the work so the fume rises away from the face.
• Respiratory protection: where fume cannot be controlled enough, use suitable respirators, such as powered air-purifying respirator welding helmets, under a respiratory protection program.
• Monitoring: carry out air sampling to confirm exposures are below limits, especially for stainless steel and confined space work.

Example of Welding Fume

A fabrication shop that had switched from mild steel to mostly stainless steel work relied on roof fans for ventilation. An industrial hygiene survey found hexavalent chromium exposures above the OSHA action level for several welders.

The shop installed fume extraction arms at each welding bay, trained welders to position the hoods within a short distance of the arc and provided powered air-purifying respirator helmets for welding inside large tanks. Follow-up sampling showed exposures well below the action level, and the shop added welders to a medical surveillance program as required by the chromium standard.

Frequently Asked Questions: Welding Fume

Is welding fume from mild steel safe?

No. IARC's Group 1 classification covers welding fume generally, including mild steel. Mild steel fume also contains manganese, which can damage the nervous system.

Is general ventilation enough to control welding fume?

Usually not for indoor welding. Open doors and roof fans dilute fume but do little to keep it out of the welder's breathing zone. Local exhaust ventilation at the source is far more effective.

What is metal fume fever?

It is a short-term, flu-like illness caused by breathing metal oxide fume, most often zinc oxide from welding galvanized steel. Symptoms include fever, chills and aches that usually appear several hours after exposure.