Welding ?smoke? is a mixture of very fine particles and gases. This ?smoke? can contain, such materials as chromium, nickel, arsenic, asbestos, manganese, silica, beryllium, cadmium, nitrogen oxides, phosgene, acrolein, fluorine compounds, carbon monoxide, cobalt, copper, lead, ozone, selenium, and zinc and they can be extremely toxic. Generally, welding fumes and gases come from the base material being welded or the filler material, but can also come from the paint and other materials on the metal being welded. Chemical reactions can also occur from the heat and even the arc light. These reactants can also be toxic.

Health effects of welding exposures can be difficult to list. The ?smoke? may contain materials not listed or assumed. The individual components of welding smoke can affect just about any part of the body, including the lungs, heart, kidneys, and central nervous system.

Exposure to metal fumes such as zinc, magnesium, copper, and copper oxide can cause metal fume fever. Symptoms of metal fume fever may occur 4 to 12 hours after exposure, and include chills, thirst, fever, muscle ache, chest soreness, coughing, wheezing, fatigue, nausea, and a metallic taste in the mouth and usually lasts a short term.

Some components of welding fumes, such as cadmium, can be fatal in a short time. Secondary gases given off by the welding process can also be extremely dangerous. Ultraviolet radiation from the welding arc reacts with oxygen and nitrogen and produces ozone and nitrogen oxides. These gases are deadly at high doses, and can also cause irritation of the nose and throat and serious lung disease.

Another reaction from the ultraviolet arc is a gas produced from chlorinated hydrocarbon solvents; this gas is called phosgene gas and even a very small amount of phosgene may be deadly.

Studies have shown that welders have an increased risk of lung cancer, and possibly cancer of the larynx and urinary tract. This risk comes from the cancer-causing agents such as cadmium, nickel, beryllium, chromium, and arsenic.

Besides chemicals being thrown off by welding, another risk can be found in the extreme heat. This intense heat can cause burns. Contact with hot slag, metal chips, sparks, and hot electrodes can cause eye injuries. Excessive exposure to heat can result in heat stress or heat stroke. Welders should be aware of the symptoms such as fatigue, dizziness, loss of appetite, nausea, abdominal pain, and irritability. Some welding may take place inside a workplace; the welder must be protected as if they were working outside in the hot sun. Ventilation, shielding, rest breaks, and drinking plenty of cool water will protect workers against heat hazards.

The intensity of the welding arc can cause damage to the retina of the eye, while infrared radiation may damage the cornea and result in the formation of cataracts. Invisible ultraviolet light from the arc can cause the white dots. The white dots, while mostly temporary, may end in blindness. Half the injuries of white dots come from people standing around the materials being welded. The intense light can even be reflected off of other objects in the area.

Even though welding generally uses low voltage, there is still a danger of electric shock. The environmental conditions of the welder, such as wet areas, may make the likelihood of a shock greater. Falls and other accidents can result from even a small shock; brain damage and death can result from a large shock.

The intense heat and sparks produced by welding can cause fires or explosions if combustible or flammable materials are in the area.

Before beginning a welding job, it is important to identify the hazards for that particular welding operation. The hazards will depend on the type of welding, the materials (base metals, surface coatings, electrodes) to be welded, and the environmental conditions. Check the Material Safety Data Sheets to identify the hazardous materials used in welding and cutting products, and the fumes that may be generated. Make sure that all possible compounds can be identified before welding begins. After identifying the hazard, appropriate control methods can be implemented.