Composition, Hazards, and Mitigation of MIG Welding Fumes

The Metal Inert Gas (MIG) welding process, also known as Gas Metal Arc Welding (GMAW), is a prevalent method in the manufacturing industry. Its versatility allows for the welding of a broad spectrum of metals, offering adaptability to both thick and thin materials. Furthermore, its capability for efficient metal deposition and high-speed welding is crucial for enhancing productivity.

However, as with all welding processes, MIG welding leads to the generation of potentially dangerous fumes, the regulation of which is mandated by health and safety institutions such as the Occupational Safety and Health Administration (OSHA)in the US, Canada’s Canadian Centre for Occupational Health and Safety (CCOHS), and various provincial bodies.

MIG welding generates a toxic and carcinogenic white fume comprised of metallic oxides and gases. The fume particles, ranging from 0.005 to 20 µm in size, can deposit throughout the respiratory system. Hence, a comprehensive ventilation strategy involving both local exhaust and general ventilation is imperative to safeguard MIG welders.

On average, the amount of fumes produced by MIG welding is moderate. Comparatively, it is more significant than that produced by Tungsten Inert Gas (TIG) or resistance welding, but less than that produced by stick welding or flux cored. This article will delve into the composition of these fumes, the hazards associated with their inhalation, and strategies to curtail exposure risks for welders and their coworkers.

Composition of MIG Welding Fumes

Fumes originate when a metal is heated past its boiling point, causing its vapors to condense into minuscule particles. The composition of the fumes produced during MIG welding is subject to several variables, such as the specific metal being welded, any surface plating or coating, the type of welding wire and consumables used, and the nature of the shielding gas employed.

Common Metals in MIG Welding Fumes

Outlined below are the metal particles frequently present in MIG welding fumes, typically existing in various oxidation states.

• Aluminum – when welding aluminum but also present in different alloys (copper, zinc, brass, steel, etc.)
• Antimony
• Arsenic (Confirmed human carcinogen)
• Beryllium – hardening agent found in many alloys (Confirmed human carcinogen)
• Cadmium – found in some stainless steels or plated materials (Suspected human carcinogen)
• Chromium – found in most stainless steels and used for plating (Chromium (VI) is a confirmed human carcinogen)
• Cobalt
• Copper – found in some alloys
• Iron
• Lead – found in some alloys and coatings on steel (Confirmed animal carcinogen)
• Manganese – especially for high-tensile steels
• Magnesium
• Molybdenum – found in different steel alloys, iron, and stainless steel (Confirmed animal carcinogen)
• Nickel – found in stainless steel and high-alloy materials
• Selenium
• Silver
• Tin
• Titanium (Titanium oxide is a confirmed animal carcinogen)
• Vanadium – found in some steel or nickel alloys and stainless steel (Vanadium pentoxide is a confirmed animal carcinogen)
• Zinc – especially for galvanized metals

It is crucial to understand the composition of each metal and coating involved in the welding process to accurately assess potential risks for employees.

Gases Frequently Present in MIG Welding Fumes

The main health threats linked with gases in welding fumes include toxicity and asphyxiation.

In the context of MIG welding, the most frequently used shielding gases are a combination of argon and carbon dioxide, with helium occasionally added to the mixture (referred to as a hot mix). However, due to the heat and radiation involved in the welding process, other hazardous gases may also be produced.

• Argon – shielding gas
• Carbon Dioxide – shielding gas
• Carbon Monoxide – formed in the arc
• Helium – shielding gas
• Hydrogen Fluoride – formed in the arc
• Nitric Oxide – formed in the arc
• Nitrogen Dioxide – formed in the arc
• Ozone – formed in the arc
• Phosgene – formed in the arc

Argon, Helium, and Nitrogen are typically not subject to exposure limits set by health and safety agencies. However, as they are asphyxiants, maintaining a safe oxygen level (at least 19.5%) is vital when these gases are present in the workplace, a common scenario in MIG welding.

Carbon oxides and hydrogen, although also asphyxiants, are subject to strict exposure limits.

Effects of these Metals and Gases on Welders

• Allergens: Aluminum, Chromium, Nickel, Zinc, etc.
• Asphyxiants: Argon, Carbon Oxides, Helium, Hydrogen, Nitrogen, etc.
• Carcinogenic: Beryllium, Cadmium, Chromium, Nickel, etc.
• Fibrotic: Beryllium, Iron, Nitrogen Oxide, etc.
• Irritants: Cadmium, Chromium, Copper, Iron Oxide, Magnesium, Manganese, Molybdenum, Nickel, Nitrogen Oxide, Ozone, Phosgene, Zinc, etc.
• Metal Fume Fever: Aluminum, Cadmium, Copper, Iron Oxide, Magnesium, Manganese, Nickel, Selenium, Silver, Tin, Zinc, etc.
• Toxic: Cadmium, Lead, Manganese, Ozone, etc.

Composition of MIG Welding Fumes in Specific Applications

Aluminum MIG Welding Fume

Welding aluminum generates a white fume, predominantly composed of aluminum oxide. The particles of this substance in welding fume typically measure between 0.01 to 0.1 microns and can be inhaled and will deposit throughout the respiratory system.

The process also produces ozone, a toxic gas that forms when the ultraviolet radiation generated during welding interacts with the air. Aluminum’s reflectiveness intensifies this reaction.

While the aluminum welding fume contains several other metals and gases as previously discussed, aluminum oxide and ozone generally pose the greatest challenges. Without appropriate protection, welding aluminum can cause respiratory and lung diseases such as aluminosis and potentially affect the nervous system.

Galvanized Steel MIG Welding Fume

Inhalation of zinc oxide is a leading cause of metal fume fever, likely the most common occupational disease among welders. As galvanized steel is zinc-coated, it is notorious for causing sickness in welders; some companies even avoid working with this material due to this reason.

Lead oxide, a carcinogen, is also commonly found in galvanized steel welding fume and should be effectively extracted.

These pollutants usually take precedence when controlling galvanized steel MIG welding fume.

High-Tensile and Low-Alloy Steel MIG Welding Fume

MIG welding fume often contains manganese (in various oxidation states), becoming especially problematic when welding high-tensile and low-alloy steels, ferrous alloys, or certain copper, aluminum, and nickel alloys, which can sometimes contain up to 16% manganese (although that is quite rare).

Manganese particles in welding fumes typically measure between 0.001 and 100 µm and can deposit throughout the respiratory system. Long-term inhalation of toxic manganese fumes can lead to severe health issues, including Manganism (Parkinson-like symptoms), and damage to the lungs, liver, and kidneys.

If the manganese concentration exceeds the threshold limit value recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) of 0.02 mg/m3, it becomes critical to reduce it.

Stainless Steel MIG Welding Fume (and welding of other metals that contain chromium)

When MIG welding stainless steel, the primary concern is the presence of the highly toxic hexavalent chromium (also known as chromium VI) in the fume. High temperatures convert chromium into a hexavalent state. The ACGIH classifies hexavalent chromium as a known human carcinogen and recommends a threshold limit value of 0.02 µg/m3.

While this is not the only danger present in the fume when MIG welding stainless steel, it is typically the first one to be addressed.

Potential Health Risks & Issues Associated with MIG Welding Fumes

MIG welding has the potential to cause illness in welders. Short-term effects can include metal fume fever, while long-term consequences may include conditions such as Manganism and various types of cancer. In the absence of proper ventilation, MIG welding, especially indoors or within confined spaces where fume concentration escalates to harmful levels, is unsafe.

The health risk for a welder exposed to welding fumes and gases depends on their composition, concentration, and exposure duration.

Agencies such as OSHA, the Centers for Disease Control and Prevention, the International Agency for Research on Cancer, and the CNESST suggest that inhaling welding fumes may lead to health issues such as:

• Accumulation of fluid in the lungs
• Aluminosis (an incurable respiratory disease)
• Anthracosis (poisoning after inhalation of carbon dust)
• Asthma
• Berylliosis (poisoning after inhalation of beryllium dust)
• Bleedings
• Bone and joint disorders
• Chest pain
• Dermatitis or eczema
• Dizziness and nausea
• Eye, nose, and throat irritation
• Kidney damage and disease
• Lung damage
• Manganism (caused by manganese, symptoms similar to Parkinson’s disease)
• Metal fume fever (flu-like symptoms typically occur 4 to 10 hours after exposure)
• Nervous system damage
• Respiratory issues that could lead to suffocation or asphyxiation
• Siderosis (presence of iron oxide in lung tissue after inhalation)
• Stannosis (presence of tin oxide in lung tissue after inhalation)
• Stomach ulcers
• Various types of cancer (lung, kidney, etc.)
• Welder’s lung or pneumosiderosis (caused by iron oxide)

Mitigating Exposure to MIG Welding Fumes

Here are several tips to protect welders and other workers from potential health problems caused by MIG welding fumes:

1. Weld only when essential. Consider alternatives to manual welding, such as bolts, fasteners, or robotic welding.

2. Isolate welding operations to protect other workers (use a dedicated welding area or building, or use welding screens).

3. When possible, use TIG or resistance welding instead of MIG. Otherwise, adjust the welding parameters to minimize fumes. For instance, pulsed mode generates less toxic fume than conventional MIG processes. Lowering the welding power and reducing the carbon dioxide in the shielding gas mix can also decrease fume production.

4. Use materials and consumables that generate less toxic fumes. Always remove paint or coatings before welding (consult your supplier for the safest methods). Also, avoid carcinogenic (arsenic, beryllium, cadmium, hexavalent chromium, lead, etc.) and toxic substances.

5. Install welding fume extractors, preferably fume extraction MIG guns or fume extraction arms. Refer to our article about the top MIG welding fume extractors for more information.

6. Instruct welders to position themselves to avoid inhaling fumes and gases. For example, they should keep their head away from the weld pool and the flexible arm’s inlet, and use wind direction to disperse fumes when welding outdoors.

7. Ensure proper ventilation in your workspace. An hourly air exchange rate of four to 12 (20 in confined spaces) is generally adequate to maintain air quality within health and safety standards when combined with local exhaust ventilation.

8. Use personal protective equipment such as masks and respirators when previous measures are insufficient to reduce exposure to safe levels. Each piece of equipment should be fitted individually for each worker and should only be used as a last resort.

For more details, refer to our article covering 8 Steps to Solve Welding Fume Problems.

Regulatory Obligations for Employers: Exposure Limits in the US and Canada

Permissible exposure limits for welding fumes, metal fumes, and gases are regulated by health and safety agencies (such as OSHA) across North America. You can find more about the maximum allowed concentrations in the following articles:

• Welding Fume Regulations and Exposure Limits in the US
• Welding Fume Regulations and Exposure Limits in California
• Welding Fume Regulations and Exposure Limits in Canada

These articles also include recommendations from the American Conference of Governmental Industrial Hygienists (ACGIH). The mentioned concentrations are deemed safe for welders working no more than 8 hours daily in a typical environment.

In the United States, OSHA and Cal/OSHA enforce a permissible exposure limit for welding fume at 5 mg/m3 (an 8-hour time-weighted average). In Canada, the Northwest Territories, Nunavut, Quebec, Saskatchewan, and Yukon health and safety agencies set the exposure limit for welding fume at 5 mg/m3. Other provinces and territories follow ACGIH recommendations, except Alberta, which maintains that exposure should be kept as low as reasonably achievable.

Most hazardous substances found in welding fumes and covered in this article also have their own exposure limits, such as chromium, manganese, etc.

Any Questions?

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