Welding fumes contain a mixture of metal oxides, gases, and particulates that cause both immediate and long-term health damage. Every welding process produces fumes, and the composition varies based on the base metal, filler metal, coatings, and welding parameters. Understanding what’s in the fume plume and how to control exposure is not optional safety training. It’s basic self-preservation.
In 2017, the International Agency for Research on Cancer (IARC) reclassified all welding fumes as Group 1 carcinogens (carcinogenic to humans), regardless of the base metal. That classification applies to mild steel welding too, not just stainless or exotic alloys.
What’s in Welding Fumes
Welding fumes are formed when metals in the weld pool vaporize, then condense into fine particles as they cool in the air. These particles are typically 0.1 to 1 micrometer in diameter, small enough to penetrate deep into the lungs.
The composition depends on what you’re welding:
| Base/Filler Metal | Primary Fume Components | Key Health Concern |
|---|---|---|
| Carbon steel (E7018, ER70S-6) | Iron oxide, manganese oxide, silicon dioxide | Manganese (neurological), iron (siderosis) |
| Stainless steel (308L, 316L) | Chromium (Cr VI), nickel, iron oxide, manganese | Hexavalent chromium (cancer), nickel (cancer) |
| Galvanized steel | Zinc oxide, iron oxide | Zinc (metal fume fever) |
| Aluminum | Aluminum oxide | Respiratory irritation |
| Cadmium-plated/brazed | Cadmium oxide | Cadmium (acute: fatal pulmonary edema; chronic: kidney/lung) |
| Lead-painted surfaces | Lead oxide | Lead poisoning (neurological, organ damage) |
| Copper alloys (bronze, brass) | Copper oxide, zinc oxide | Metal fume fever, respiratory irritation |
In addition to metal fumes, welding produces gases:
- Ozone (O3): Formed by UV radiation from the arc, especially with GMAW and GTAW on aluminum. Strong respiratory irritant.
- Nitrogen oxides (NOx): Formed in the arc environment. Respiratory irritant, can cause pulmonary edema at high concentrations.
- Carbon monoxide (CO): Produced by CO2 shielding gas decomposition and cellulose electrode coatings (E6010). Displaces oxygen, causes headaches and impaired judgment.
- Phosgene: Formed when chlorinated solvents near the arc decompose. Extremely toxic. Never weld near degreasing chemicals.
Health Effects by Contaminant
Manganese
Manganese is present in virtually every steel welding fume at concentrations of 5-20% of the total fume. The OSHA PEL is 5 mg/m3 (ceiling), but ACGIH recommends a TLV of 0.02 mg/m3 (respirable fraction), which is 250 times lower. Many occupational health experts consider the OSHA PEL inadequate.
Chronic manganese overexposure causes manganism, a neurological condition resembling Parkinson’s disease. Symptoms develop gradually:
- Early: fatigue, irritability, difficulty concentrating, mood changes
- Intermediate: tremor, slowed movement, balance problems
- Advanced: mask-like facial expression, rigid muscles, speech changes
Manganism is irreversible. Once neurological damage occurs, it doesn’t improve after exposure stops. This is the biggest under-recognized risk in carbon steel welding.
Hexavalent Chromium (Cr VI)
Generated when welding stainless steel, chrome alloys, and chrome-containing filler metals. The OSHA PEL is 5 micrograms/m3 (0.005 mg/m3) as an 8-hour TWA. This is an extremely low limit, and exceeding it during stainless steel welding is easy without proper controls.
Health effects:
- Cancer: Confirmed lung carcinogen (IARC Group 1)
- Respiratory: Nasal septum ulceration and perforation, asthma, bronchitis
- Skin: Dermatitis, skin ulcers (“chrome holes”)
- Other: Kidney damage, reproductive effects
Cr VI exposure requires medical surveillance, air monitoring, and specific engineering controls under OSHA’s Chromium (VI) standard (29 CFR 1910.1026).
Zinc Oxide (Metal Fume Fever)
Welding or cutting galvanized steel releases zinc oxide fumes. Exposure causes metal fume fever, which mimics flu symptoms 4-12 hours after exposure: chills, fever, muscle aches, nausea, fatigue. Recovery typically takes 24-48 hours. Repeated exposure in the same week may confer temporary tolerance, which wears off over weekends. Read our galvanized steel welding safety guide for detailed prevention measures.
Cadmium
Found in some brazing alloys, plated metals, and certain silver solders. Cadmium is acutely lethal. A single heavy exposure can cause fatal pulmonary edema (fluid in the lungs), sometimes with a delayed onset of 24-72 hours. The danger is that symptoms may be mild initially, then worsen dramatically.
OSHA PEL: 5 micrograms/m3 (8-hour TWA). Action level: 2.5 micrograms/m3.
Any work involving cadmium-containing materials requires respiratory protection, air monitoring, and medical surveillance. If you suspect cadmium exposure and develop flu-like symptoms, seek medical attention immediately and tell them about the exposure.
OSHA Permissible Exposure Limits
| Substance | OSHA PEL (8-hr TWA) | ACGIH TLV (8-hr TWA) | Notes |
|---|---|---|---|
| Total welding fumes | 5 mg/m3 | N/A (component-specific) | OSHA general fume limit |
| Manganese | 5 mg/m3 (ceiling) | 0.02 mg/m3 (respirable) | OSHA limit widely considered too high |
| Hexavalent chromium | 5 ug/m3 | 25 ug/m3 | Separate Cr VI standard applies |
| Nickel (soluble) | 1 mg/m3 | 0.1 mg/m3 (inhalable) | Carcinogen (IARC Group 1) |
| Zinc oxide (fume) | 5 mg/m3 | 2 mg/m3 (respirable) | Metal fume fever threshold |
| Cadmium | 5 ug/m3 | 10 ug/m3 (total) | Fatal at acute high doses |
| Iron oxide (fume) | 10 mg/m3 | 5 mg/m3 (respirable) | Causes siderosis (benign pneumoconiosis) |
| Ozone | 0.1 ppm | 0.05 ppm (heavy work) | Highest with GMAW aluminum |
Note: OSHA PELs were largely established in the 1970s and haven’t been updated for many substances. ACGIH TLVs are generally more protective and reflect current science. Many employers use ACGIH values as their internal standards.
Ventilation Requirements
OSHA 29 CFR 1910.252(c) requires mechanical ventilation when welding in enclosed spaces, when welding metals that produce hazardous fumes, or when natural ventilation is insufficient.
General Mechanical Ventilation
Minimum 2,000 CFM per welder, or enough to maintain visibility (you should be able to see clearly). This is the baseline for mild steel welding in a large, open shop.
Local Exhaust Ventilation (LEV)
More effective than general ventilation. A capture hood or extraction arm positioned within 12-18 inches of the arc captures fumes at the source.
- Minimum capture velocity: 100 FPM at the welding point
- Extraction rate: Typically 500-1,000 CFM per hood
- Position the hood to one side or behind the fume plume (not between you and the weld)
LEV is required when:
- Welding stainless steel, chrome alloys, or nickel alloys
- Welding galvanized or cadmium-plated metals
- Working in spaces with ceilings lower than 16 feet
- More than one welder is working in the same area
Confined Space Ventilation
Welding in confined spaces (tanks, vessels, pipe, enclosed structures) requires forced ventilation regardless of the base metal. Natural ventilation is never sufficient. See our confined space welding guide for detailed requirements.
Respiratory Protection
When engineering controls (ventilation) can’t reduce exposure below PELs, respiratory protection is required.
Respirator Selection Hierarchy
Powered Air-Purifying Respirator (PAPR) with welding helmet: Best option for extended welding. Supplies filtered air under positive pressure, so fumes can’t leak in around the seal. Assigned Protection Factor (APF) = 25-1000 depending on type.
Half-face APR with P100 filters: Common and effective for most welding. APF = 10 (reduces exposure by 10x). Adequate for many mild steel applications but may not suffice for stainless steel welding.
N95 disposable respirator: Better than nothing, but APF = 10 and fit is unreliable under a welding helmet. Not recommended as a primary control for full-time welding.
Supplied Air Respirator (SAR): Required in confined spaces or where air is oxygen-deficient. Provides clean breathing air from an external source.
Important Respirator Rules
- Respirator use requires a written respiratory protection program (OSHA 1910.134)
- Medical evaluation before first use
- Annual fit testing for tight-fitting respirators
- Training on proper use, maintenance, and limitations
Reducing Fume Exposure: Practical Steps
Position yourself upwind of the plume. Fume rises and drifts. Don’t lean over the weld. Keep your head to the side of the fume column.
Use the lowest effective amperage. Higher amps = more fume. If you can produce acceptable welds at lower settings, do so.
Choose lower-fume processes when possible. GTAW produces less fume than SMAW. Pulsed GMAW produces less than conventional spray transfer. The fume generation rate varies significantly by process.
Use lower-fume filler metals. Some electrode classifications generate less fume than others. E7018 produces less fume than E6010. ER70S-6 produces less than some flux-cored wires.
Grind coatings before welding. If welding galvanized, lead-painted, or cadmium-plated material, grinding the coating off for 2-4 inches on each side of the joint before welding eliminates the most hazardous fumes at the source.
Keep your head out of the plume. This is the simplest and most effective single action. If you can see the fume drifting past your face, reposition.
Fume Generation Rates by Process
Not all welding processes produce equal amounts of fume. The process, filler metal, and parameters all affect how much fume enters the air:
| Process | Typical Fume Generation Rate | Notes |
|---|---|---|
| SMAW (E6010) | 0.5-1.5 g/min | Cellulose coating produces heavy fume and CO |
| SMAW (E7018) | 0.3-0.8 g/min | Low-hydrogen coating, less fume than cellulose |
| FCAW (gas-shielded) | 0.4-1.0 g/min | Moderate fume, varies by wire classification |
| FCAW (self-shielded) | 0.5-1.5 g/min | Higher fume than gas-shielded FCAW |
| GMAW (spray transfer) | 0.3-0.7 g/min | Moderate fume, higher at high amperages |
| GMAW (pulsed) | 0.2-0.4 g/min | Lower fume than spray or short-circuit |
| GTAW | 0.01-0.05 g/min | Lowest fume of any arc process |
| SAW | 0.1-0.3 g/min | Low, flux blanket traps most fume |
GTAW (TIG) produces 10 to 100 times less fume than SMAW or FCAW. If fume exposure is a primary concern and the application allows it, switching to TIG dramatically reduces the fume load. When TIG isn’t practical, pulsed GMAW is the next-best option for fume reduction.
Medical Surveillance
OSHA requires medical surveillance for workers exposed to certain substances above their action levels:
- Hexavalent chromium (1910.1026): Medical surveillance when exposure exceeds 2.5 ug/m3 (action level). Includes respiratory questionnaire, pulmonary function testing, and examination of the nasal passages
- Cadmium (1910.1027): Blood and urine cadmium levels when exposure exceeds 2.5 ug/m3
- Lead (1910.1025): Blood lead levels when exposure exceeds 30 ug/m3
Even when not legally required, welders who work with toxic fumes should get baseline pulmonary function testing and periodic follow-up. Detecting reduced lung function early allows you to change practices before permanent damage occurs.
Welding fume exposure is cumulative over a career. The damage from manganese, chromium, and other metals builds up over years and decades. The time to protect yourself is now, not after symptoms appear. Every shop should have adequate ventilation, access to respirators, and a clear policy on fume control. If your shop doesn’t, that’s a problem worth bringing up.