 Welders are often exposed to dangerous gases and particulate matter . Processes like flux @-@ cored arc welding and shielded metal arc welding produce smoke containing particles of various types of oxides . The size of the particles in question tends to influence the toxicity of the fumes , with smaller particles presenting a greater danger . This is because smaller particles have the ability to cross the blood brain barrier . Fumes and gases , such as carbon dioxide , ozone , and fumes containing heavy metals , can be dangerous to welders lacking proper ventilation and training . Exposure to manganese welding fumes , for example , even at low levels ( < 0 @.@ 2 mg / m3 ) , may lead to neurological problems or to damage to the lungs , liver , kidneys , or central nervous system . Nano particles can become trapped in the alveolar macrophages of the lungs and induce pulmonary fibrosis . The use of compressed gases and flames in many welding processes poses an explosion and fire risk . Some common precautions include limiting the amount of oxygen in the air , and keeping combustible materials away from the workplace . 
