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SAFETY IN WELDING 1.00

Welding fumes

Welding fumes, or smoke consists of a mixture of gases and dust particles. The composition of the fumes depends on: 1. The filler material and method of welding.

2. The base material.

Different welding methods and different metals, means that the fumes given off may contain numerous components which can be dangerous if inhaled. The best protection is the use of a smoke extraction unit. When correctly positioned, this unit will protect the welder against fume inhalation and also prevent the smoke spreading in the surrounding area and contaminating the area for others. If it is not possible to use a smoke extraction unit, the welder can minimize the risk of fume inhalation by positioning himself so that the smoke rises some distance from his nose and mouth or by using a welding face shield with fresh air supply. For on board use a self contained unit with filter is a safe and flexible solution. Electric arc welding with coated electrodes, may comprise several different components depending on the type of electrode. The composition of the smoke will therefore vary depending on the type of electrode. Electrodes are divided into smoke classes 1 to 7, which indicates the degree of smoke pollution. See the Coated Electrodes

section on smoke classes.

Risks

The fumes given off when welding unalloyed or low-alloyed steel which has not been surface treated, are not considered to be particularly dangerous as long as inhalation of these

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fumes is kept at a reasonable level. When the base metal has been surface-treated, the smoke may contain substances which could constitute a health risk.

Welding of galvanized materials or materials surface treated with substances containing zinc, gives off fumes which contain zinc oxide. Inhalation of these fumes can result in zinc poisoning with very unpleasant effects. It should be avoided by the use of a good extraction unit, or the use of a face shield with fresh air connection.

Cadmium plating is sometimes used instead of zinc plating. Welding or cutting cadmium-plated material can produce fumes which contain cadmium oxide. Lung damage can result from the inhalation of this substance. When welding or cutting old steel plating, remember that the surface coating may contain lead or mercury. Fumes from these substances can result in serious health damage if inhaled.

When welding or cutting any type of material that has been plated or surface coated, precautions must be taken against dangerous fumes before welding commences. Welding of stainless or acid-resistant steel produces smoke containing nickel and chrome. Copper alloys (tin bronze, leaded gun metal, leaded tin bronze and brass) contains items such as tin, zinc, lead, etc. Welding temperature tends to vaporise these items. Inhaling these substances can seriously affect the respiratory system. When weIding these types of steel or materials plated or coated with substances containing chrome, c­ admium, nickel lead or mercury, it is essential