Welding is a widespread industrial process that joins metals together using high levels of heat, pressure or both. There are numerous welding processes and process variants (Burgess, 1995); common methods include shielded manual metal arc welding (MMAW; also known as stick welding), gas metal arc welding (GMAW; or metal inert gas welding), ux-cored arc welding and gas tungsten arc welding (GTAW; or tungsten inert gas welding). The process used depends on a variety of factors, including the type, form and thickness of the metal being welded. While there are no ofcial global estimates, some have estimated that there are 2-3 million full-time welders worldwide (Solano-Lopez et  al., 2006; Szram et  al., 2013). The true number is probably much higher, since many trades without the title ‘welder’ regularly include welding; examples include assemblers, fabricators, boilermakers, pipetters, steamtters and sheet metal workers. In addition, many non-welders are exposed to respiratory hazards while working in the vicinity of welders.