Metal Inert Gas (also called MIG or GMAW) is the most common welding process in the manufacturing industry. It is very versatile and enables the welding of a wide range of metals, works well for thick or thin materials, and allows good metal deposition and welding speed, which is essential to increase productivity.
However, like any welding process, it generates hazardous fumes that need to be controlled as required by health and safety organizations such as OSHA in the US or CCOHS and provincial agencies in Canada.
MIG welding produces a white toxic and carcinogenic fume composed of metal oxides and gases. Particles in the fume are between 0.005 to 20 µm in size and may deposit throughout the respiratory system. Therefore, a combination of local exhaust and general ventilation is necessary to protect MIG welders.
Metal Inert Gas welding generally produces an average amount of fume. As a comparison, it is usually worse than TIG or resistance welding but better than stick welding or flux cored. This article will discuss the fume composition, the risks of inhaling it, and a method to reduce the risk of exposure for welders and their colleagues.
MIG welding fume composition
Fumes are formed when a metal is heated above its boiling point, and its vapors condense into very fine particles. The fume composition when welding with the MIG process will depend on many factors, including the type of metal being welded, the presence of surface plating or coating, the welding wire, the consumables, and the shielding gas used.
Metals commonly found in MIG welding fumes
Here is a list of metal particles found in many cases in the fume when MIG welding. They will be found in various oxidation states.
- Aluminum – when welding aluminum but also present in different alloys (copper, zinc, brass, steel, etc.)
- 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)
- Copper – found in some alloys
- Lead – found in some alloys and coatings on steel (Confirmed animal carcinogen)
- Manganese – especially for high-tensile steels
- Molybdenum – found in different steel alloys, iron, and stainless steel (Confirmed animal carcinogen)
- Nickel – found in stainless steel and high-alloy materials
- 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
Knowing the composition of each metal and coating involved in the welding process is essential to assess the risk for employees.
Gases commonly found in MIG welding fumes
Two primary health risks are associated with gases in welding fume: toxicity and asphyxiation.
When it comes to MIG welding, the most common shielding gases combine argon and carbon dioxide. Sometimes helium can also be added to the mix (hot mix). But the welding process can generate other dangerous gases because of the heat and radiation.
- 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 usually not submitted to an exposure limit by health and safety agencies. But since they are asphyxiants, the oxygen level must be maintained to a safe level (at least 19.5%) when these gases are present in the workplace, which is often the case with MIG welding.
Carbon oxides and hydrogen are also asphyxiants but must be kept below strict exposure limits anyway.
Effects of these metals and gases on welders
- Toxic: lead, manganese, cadmium, ozone, etc.
- Carcinogenic: chromium, cadmium, beryllium, nickel, etc.
- Metal fume fever: zinc, copper, magnesium, aluminum, cadmium, iron oxide, manganese, nickel, selenium, silver, tin, etc.
- Allergens: chromium, nickel, zinc, aluminum, etc.
- Asphyxiants: argon, carbon oxides, nitrogen, helium, hydrogen, etc.
- Fibrotic: beryllium, iron, nitrogen oxide, etc.
- Irritants: ozone, nitrogen oxide, iron oxide, molybdenum, nickel, phosgene, cadmium, chromium, copper, manganese, magnesium, zinc, etc.
MIG welding fume composition for more specific applications
Aluminum MIG welding fume
When welding aluminum, a white fume is produced. It is mainly composed of aluminum oxide. Aluminum oxide particles in welding fume are usually between 0.01 to 0.1 microns, can easily be inhaled, and will deposit throughout the respiratory system.
The process also produces ozone which is a toxic gas. Ozone is formed when the ultraviolet radiation generated while welding interacts with the air. Aluminum’s reflectiveness magnifies this reaction.
Although aluminum welding fume will also be composed of many other metals and gases introduced earlier, which must also be controlled, aluminum oxide and ozone are usually the two most challenging ones in this case. Welding aluminum without appropriate protection can cause respiratory and lung diseases like aluminosis and affect the nervous system, among other things.
Galvanized steel MIG welding fume
Zinc oxide inhalation is one of the most important causes of metal fume fever, which is likely the most common occupational disease amongst welders. Since galvanized steel is coated with zinc, it is famous for getting welders sick, and some companies even refuse to work with this material for this reason.
It is not rare to find lead oxide in galvanized steel welding fume. It is carcinogenic and must also be extracted efficiently.
These pollutants tend to become the priority when it comes to controlling galvanized steel MIG welding fume.
High-tensile and low-alloy steel MIG welding fume
In most cases, MIG welding fume contains manganese (in various oxidation states). But it can become very problematic when welding high-tensile and low-alloy steels, ferrous alloys, or some copper, aluminum, and nickel alloys which sometimes contain as much as 16% manganese.
Manganese particles in welding fumes are usually between 0.001 and 100 µm. Therefore, they may deposit throughout the respiratory system. If inhaled for a prolonged period, toxic manganese fumes can have devastating health effects, including Manganism (Parkinson–like symptoms) and damage to the lungs, liver, and kidneys.
Whenever manganese concentration exceeds the threshold limit value recommended by the American Conference of Governmental Industrial Hygienists (ACGIH), which is 0.02 mg/m3, it becomes a priority to reduce it.
Stainless steel MIG welding fume (and welding of other metals that contain chromium)
The main danger when MIG welding stainless steel is the presence of highly toxic hexavalent chromium, also called chromium (VI), in the fume. Chromium is converted to a hexavalent state by high temperatures. According to the American Conference of Governmental Industrial Hygienists (ACGIH), hexavalent chromium is a known carcinogen for humans, and they recommend a threshold limit value of 0.02 µg/m3.
Once again, this is not the only danger in the fume to consider when MIG welding stainless steel, but it is usually the first one to address.
If you have any questions about welding fume, do not hesitate to contact us. We will be happy to give you some insight, and we can even visit you for free in the US and Canada.
MIG welding fume risks & health issues
MIG welding can make welders sick. They can have short-term effects like metal fume fever or long-term effects like Manganism and cancer. Without proper ventilation, it is never safe to MIG weld, especially indoors, let alone in confined spaces where fume concentration rises to dangerous levels.
The risk for a welder breathing welding fume and gases will depend on their composition, concentration, and duration of exposure.
- Eye, nose, and throat irritation
- Dizziness and nausea
- Breathing difficulties that could lead to suffocation or asphyxiation
- Metal fume fever (flu-like symptoms typically occur 4 to 10 hours after exposure)
- Lung damage
- Various types of cancer (lung, kidney, etc.)
- Stomach ulcers
- Kidney damage
- Nervous system damage
- Manganism (caused by manganese, symptoms like Parkinson’s disease)
- Chest pain
- Dermatitis or eczema
- Kidney disease
- Bone and joint disorders
- Welder’s lung or pneumosiderosis (caused by iron oxide)
- Aluminosis (incurable respiratory disease)
- Siderosis (iron oxide in lung tissue after inhalation)
- Stannosis (tin oxide in lung tissue after inhalation)
- Anthracosis (poisoning after inhalation of carbon dust)
- Berylliosis (poisoning after inhalation of beryllium dust)
- Accumulation of fluid in the lungs
Reducing MIG welding fume exposure
Here are a few tips to sustainably protect welders and other workers around from cancer and other health problems caused by MIG welding fume:
1. Only weld when it is necessary. Other processes can sometimes replace manual welding (bolts, fasteners, robotic welding).
2. Isolate welding operations from other workers (have an area or building dedicated to welding only, for example, or at least use welding screens).
3. Use TIG or resistance welding instead of MIG whenever possible. Otherwise, you can optimize the welding parameters to reduce fumes. For example, the pulsed mode generates less toxic fume than the conventional MIG process. Lowering the welding power whenever possible will also help. Reducing the fraction of carbon dioxide in the shielding gas mix causes a decrease in the quantity of fume.
4. Use consumables and materials that produce less toxic fume. For example, you should always remove paint or coatings before welding (contact your supplier to ask for the safest way to do so). Also, avoid carcinogenic (arsenic, beryllium, cadmium, hexavalent chromium, lead, etc.) and toxic substances.
5. Use welding fume extractors, ideally fume extraction MIG gun, otherwise fume extraction arms. For more information, see our general article about the best MIG welding fume extractors.
6. Make sure welders position themselves to avoid breathing fumes and gases. For example, they should not leave their head between the weld pool and the flexible arm. Or they can use the wind to drive the fumes away when welding outside.
7. Make sure your factory is adequately ventilated. An hour exchange rate between four and 12 (20 in confined spaces) will usually be sufficient to keep the air quality within applicable health and safety standards when combined with local exhaust ventilation.
8. Use personal protective equipment such as masks and respirators if the previous measures are insufficient to reduce exposure to safe levels. They should be fitted for each worker individually and only used as a last resort.
You can read our article 8 Steps to Solve Welding Fume Problems for more details.
Employer’s obligation: exposure limits in the US and Canada
Permissible exposure limits for welding fume, metal fume, and gases are regulated and are enforced by health and safety agencies like OSHA everywhere In North America. To know more about the maximum concentrations allowed, you can read one of 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
In these articles, you will also find recommendations from the American Conference of Governmental Industrial Hygienists (ACGIH). These concentrations are considered safe nowadays if the welder does not work more than 8 hours a day and welds in a typical environment.
In the United States, the permissible exposure limit for welding fume enforced by OSHA and Cal/OSHA is 5 mg/m3. It is the 8 hours time-weighted average. In Canada, health and safety agencies in the Northwest Territories, Nunavut, Quebec, Saskatchewan, and Yukon set the exposure limit for welding fume at 5 mg/m3. Other provinces and territories follow the ACGIH recommendations, except for Alberta, which requires keeping it as low as reasonably possible.
Most hazardous substances found in welding fumes and introduced on this page are also subjected to their exposure limit, such as chromium, manganese, etc.
Feel free to contact us. We will help you protect your workers and comply with welding fumes standards anywhere in the US and Canada.