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Exposure to fume

02/26/201511:57   

Exposure to fume

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For many gas and arc welding processes, the fume concentration in the immediate vicinity of the weld is well above its exposure limit. The amount of fume generated is determined primarily by welding process, consumable and welding procedure. However, the following aspects are likely to influence the degree to which the welder is exposed to fume:

  • welding position
  • location and type of workplace
  • exposure duration

Thus, welders using the same process may be exposed to different levels of fume. The risks for each job should, therefore, be assessed individually.

Welding position

The welding position (flat, vertical, horizontal or overhead) and proximity of the welder to the fume plume affect exposure. As the welder naturally bends over the workpiece, the flat position induces the highest level of fume in the breathing zone. The welder should adopt a working position which ensures that his head is away from the plume.

Location and type of workplace

Welding in a large workshop, or outdoors, prevents build-up of fume and gases. However, in a small workshop, fume will not be readily dispersed and the welder may be subjected to a higher than average exposure. Working in confined spaces, in particular, requires an efficient, monitored, ventilation system so exposure is controlled and there is no depletion of oxygen in the working atmosphere.

Exposure duration

Long and short term Occupational Exposure Limits (OELS) given in Job Knowledge for Welders No. 31 relate to the average concentration over an eight hour period. Exposure will be intermittent, mainly during the arcing period. There should be relatively little exposure between arcing periods but this may be influenced by the presence of other welders, effectiveness of control measures and general ventilation. Furthermore, as the work pattern (arcing time and down time) vary from day to day, average exposure may often only be assessed by frequent sampling.