Welding Fume Facts: What It Is and What It Does to You
Welding fume is a complex mixture of very small metal particles and gases created during welding. Its composition depends on the welding process, base metal, filler material, coatings and work environment. Health risk depends mainly on what is in the fume, how concentrated it is and how long a worker is exposed.
What Is Welding Fume?
Welding fume is produced when intense heat vaporizes small amounts of metal and other materials used during welding. As those vapors cool, they condense into extremely small airborne particles.
NIOSH describes welding emissions as a complex mixture of metals, metal oxides and other chemical species that can come from the base metal, welding electrode, wire, flux or surface coatings.
The exact fume composition can vary considerably from one welding application to another. Mild steel, stainless steel, galvanized material and coated metals can all generate different combinations of contaminants.
Learn more in Welding Fumes 101 .
What Gases Can Be Generated During Welding?
Welding and cutting operations can generate gases in addition to metal particles. Depending on the process and shielding method, these may include:
- Ozone
- Nitrogen oxides
- Carbon monoxide
- Carbon dioxide
- Shielding gases such as argon or helium
Shielding gases are not necessarily toxic in the same way as some welding contaminants, but they can create an oxygen-deficiency hazard if they accumulate in poorly ventilated or confined spaces.
What Metals Can Be Present in Welding Fume?
The metals present depend on what is being welded and which consumables are used. Welding fumes may contain:
- Iron
- Manganese
- Chromium
- Nickel
- Zinc
- Copper
- Lead
- Cadmium
- Beryllium
NIOSH notes that welding involving stainless steel, cadmium-coated steel, lead-coated steel or metals containing nickel, chromium, zinc and copper can produce fumes that are more hazardous than typical mild-steel welding fumes.
What Determines the Risk From Welding Fume?
The health risk from welding fume is not determined by one factor alone. NIOSH identifies several important variables, but three are especially useful when assessing exposure:
- Toxicity: What contaminants are present?
- Concentration: How much contaminant is in the breathing zone?
- Duration: How long and how often is the worker exposed?
These factors work together. A relatively short exposure to a highly hazardous contaminant may still be important, while repeated exposure to lower concentrations can also create long-term risk.
How Toxic Can Welding Fume Be?
Welding fume toxicity depends heavily on the materials involved. There is no single toxicity level that applies to every type of welding fume.
For example, mild-steel welding fumes are often dominated by iron with smaller amounts of manganese and other elements. Stainless-steel welding can introduce chromium and nickel into the fume. Welding coated or plated metals can generate additional hazardous contaminants.
Many individual metals and compounds have occupational exposure limits established by OSHA, NIOSH or other safety authorities.
Why Is Fume Concentration Important?
Welding-fume concentration is usually highest close to the point where the fume is generated. The rising plume can pass through the welder's breathing zone if the worker is positioned directly above it.
As the plume moves away from the weld, it mixes with surrounding air and becomes diluted. However, dilution alone does not necessarily mean exposure is adequately controlled.
Source capture uses local exhaust ventilation to collect the fume close to the welding operation before it spreads into the wider workspace.
NIOSH has evaluated source-capture systems and found that properly applied local exhaust ventilation can reduce welding-fume exposure.
This is also why welders are commonly advised to keep their head out of the welding plume whenever possible.
How Does Welding Time Affect Exposure?
The amount of time spent actively welding has a major effect on overall exposure.
Some fabricators may spend much of a shift measuring, fitting and preparing parts and only weld for a smaller portion of the day. Production welders may spend considerably more time with the arc active.
This active welding period is often referred to as arc time or trigger time.
In general, more arc time means more opportunity for welding fume to be generated and inhaled. However, exposure should not be assessed from arc time alone because contaminant toxicity, concentration and ventilation conditions can vary significantly.
What Does Welding Fume Do to the Body?
The health effects depend on the specific contaminants and the amount of exposure. Possible short-term and long-term effects include:
| Type of Effect | Examples |
|---|---|
| Short-term respiratory effects | Coughing, irritation and breathing discomfort |
| Metal fume fever | Flu-like illness commonly associated with exposure to certain metal oxides such as zinc oxide |
| Neurological effects | Excessive manganese exposure can affect the central nervous system |
| Chronic respiratory effects | Repeated exposure has been associated with longer-term lung and respiratory problems |
| Cancer risk | Welding fumes are classified by IARC as carcinogenic to humans |
Why Is Manganese in Welding Fume Important?
NIOSH states that most welding fumes contain at least a small percentage of manganese. The actual amount depends on the welding wire, rods, flux and base metal.
Inhaled manganese is a concern because prolonged exposure to high airborne concentrations can affect the central nervous system. NIOSH notes that high exposures may cause a Parkinsonian syndrome called manganism.
Current NIOSH guidance lists a recommended exposure limit of 1 mg/m³ as a time-weighted average and 3 mg/m³ as a short-term exposure limit for manganese.
Are Welding Fumes Carcinogenic?
Yes. The International Agency for Research on Cancer classifies welding fumes as Group 1, carcinogenic to humans.
This classification reinforces the importance of reducing unnecessary exposure, especially for workers who weld regularly over many years.
Read more in Welding Fume Classified as Carcinogenic to Humans .
How Can Welding Fume Exposure Be Reduced?
Exposure control typically uses several approaches together.
- Capture welding fumes close to the source using local exhaust ventilation
- Provide adequate general ventilation where required
- Keep the worker's head out of the fume plume
- Use work practices that reduce unnecessary exposure
- Use respiratory protection when required by the exposure assessment
For source capture equipment, see What Is a Welding Fume Extractor?
You can also compare options using Which Fume Extractor Unit Do I Need? .
Frequently Asked Questions
What is welding fume made of?
Welding fume is a mixture of very small metal particles, metal oxides and other chemical species. Its composition depends on the base metal, welding process, filler material, flux, coatings and other materials involved.
What are the three main factors that determine welding fume risk?
The three main factors are the toxicity of the contaminants, their concentration in the breathing zone, and the duration or intensity of exposure.
Where is welding fume concentration highest?
Concentration is typically highest in the plume close to the welding point. Positioning the worker's head away from the plume and capturing the fume close to the source can reduce exposure.
Does more welding time mean more exposure?
Generally, more arc or trigger time means more welding fume is generated and there is greater opportunity for exposure. Actual exposure still depends on fume toxicity, concentration and ventilation.
What is the safest way to reduce welding fume exposure?
For many welding applications, local exhaust ventilation can capture fumes close to their source before they enter the breathing zone. General ventilation, safe work practices and respiratory protection may also be required depending on the application.
Related Reading
- Health Risks Associated With Inhalation of Welding Fume Particles
- Welding Fume Health Hazards
- What Is a Welding Fume Extractor?
- Welding Fumes 101
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