Chronic conditions may comprise bronchitis, rhinitis, pulmonary oedema and pneumonia. Ozone is formed when air is exposed to ultraviolet radiation, as happens in the welding arc. Ozone may be very detrimental to health, causing pulmonary congestion, oedema, and haemorrhage. Prolonged exposure may result in severe changes in lung function. At higher concentrations, pulmonary oedema and other serious lung conditions can result.
Carbon monoxide is colourless and odourless.
The gas is an asphyxiant, causing headache, dizziness and confusion. Decomposition products may also be hazardous to health. Solvents used to clean and degrease metal before welding may release toxic gases or fumes when welding starts. Of these substances, phosgene may warrant special mention. Normal welding is unlikely to cause excessive amounts, but care should be taken to keep these substances well away from all welding work.