The welding process produces visible smoke that contains harmful metal fume and gas by-products. Welding fumes are a complex mixture of metallic oxides, silicates and fluorides. Fumes are formed when a metal is heated above its boiling point and its vapors condense into very fine, particles (solid particulates). Welding fumes generally contain particles from the electrode and the material being welded.

What are the Health Effects of Fume Exposure?
Short Term or Acute Effects:
Eye, nose and throat irritation, dizziness and nausea.
Metal Fume fever from exposure to Zinc Oxide fume caused by welding, burning, or brazing galvanized metal- Headache, fever, chills, muscle aches, thirst, nausea, vomiting, chest soreness, fatigue, gastrointestinal pain weakness and tiredness. Copper and Magnesium can cause similar effects.

Long Term or Chronic Effects are:
Respiratory tract infections have been shown to be increased in severity and frequency among welders. Chemical irritation due to exposure to metal fumes seems to be the cause of respiratory infections.
Pneumoconiosis (a chronic respiratory disease caused by inhaling metallic or mineral particles); in particular siderosis, a type of pneumoconiosis, related to inhaling iron oxide).
Certain cancers (e.g., liver, nasal, sinonasal, stomach, and lung). The International Agency for Research on Cancer (IARC) concluded that welding fumes were “possible carcinogenic to humans” Group 2B. For example welding on stainless steel, creates hexavalent chromium.
Damage to the central nervous system, when exposed to lead, manganese and aluminum fumes. Parkinson’s like symptoms
Respiratory disease from high concentrations of carbon dioxide and related oxygen deficient atmospheres (particularly in poorly ventilated places).
Chronic poisoning when certain materials are present in welding fumes such as zinc or cadmium, polychlorinated biphenyls (from decomposition of anti-corrosion oils), or decomposition products from paints

Factors that affect worker exposure to welding fumes
• Type of welding process
• Base metal and filler metals used
• Welding rod composition
• Location (outside, enclosed space)
• Welder work practices
• Air movement • Use of ventilation controls

Three Lines of Defense
Engineering Controls- Eliminate the hazard. The most preferred method. An example of this is to add ventilation to reduce contaminants from the welding operation.
Administrative Controls- The second favorite method. Control the employee’s work schedule to limit the welder’s exposure to a hazard.
PPE- The last line of defense. To limit welding fume exposure by wearing a respirator.

Ventilation
Proper ventilation can be obtained either naturally or mechanically. Natural ventilation is considered sufficient for welding and brazing operations if the work area meets these requirements:
Space of more than 10,000 square feet is provided per welder
A ceiling height of more than 16 feet
Welding is not done in a confined space
Welding space does not contain partitions, balconies or structured barriers that obstruct cross ventilation
Welders should use natural drafts along with proper positioning to keep fume and gases away from themselves and other workers.
Local Exhaust ventilation can be used to remove fume and gases from the welder’s breathing zone. Keep fume hoods, fume extractor guns and vacuum nozzles close to the plume source to remove the maximum amount of fume and gas. Keep exhaust ports away from other workers.
Consider substituting lower fume-generating or less toxic welding type or consumable. Do not weld in confined spaces. Respiratory protection may be required if ventilation and work practices do not reduce exposures to safe levels.
The best goal for any welding process is to control the individual welder’s exposure to metal fume as much as possible recognizing that OSHA PELs are just a guide, not an ultimate safe limit. Using local exhaust ventilation systems are the most effective but they’re also the tricky to design so as to not interfere with the welding process. To get the exposure levels as low as you can, it’s important to use controls that have been skillfully engineered to control the fumes for the specific welding method being used. It is also vital to monitor welders regularly to verify the effectiveness of the controls.

For further details of hazards of various fume and gas types, see chart outlining each specific hazard, https://www.ccohs.ca/oshanswers/safety_haz/welding/fumes.html