Controlling Welding Fume, A Total Systems Approach

Controlling Welding Fume, A Total Systems Approach

Introduction
Operators are exposed to fume and gases when welding, and exposures vary depending upon the process and specific working conditions. Fabricators are under continual pressure to reduce worker exposure to potentially harmful substances in the workplace, including welding fume. This article will address the following:

• How welding fume is generated
• Coordinating factors that affect fume generation and exposure to fume such as welding design, process, equipment, consumables, gases, work management and ventilation
• Highlights of fume extraction technology
• The current U.S. regulatory climate with regard to welding fume
• Current published exposure limits for typical components of fume

What Is Welding Fume?
Although many people think of gases and vapors from gasoline or other chemicals as "fume," technically, fume is comprised of very small, solid particles. Since Arc welding usually produces only small concentrations of gases, exposure to gases is seldom a concern except in confined areas. Therefore, the issue of secondary gas production will not be specifically discussed here.

Arc welding creates fume as some of the metal boils from the tip of the electrode and from the surface of molten droplets as they cross the arc. This metal vapor combines with oxygen in the air and solidifies to form tiny fume particles. These particles are visible because of their quantity, but each particle is only between 0.2 and 1.0 micron in size. Since fume primarily comes from the electrode, it consists of oxides of its metals, alloys and flux compounds. In steel welding, therefore, fume is primarily iron oxide and oxides of alloys such as manganese and chromium. With plated or coated metals, some of the fume comes from the weld pool as well. This adds oxides of metals from the base material into the fume such as zinc oxide from welding galvanized steels.

A Total Systems Approach
There are many ways to reduce exposure to welding fume. Each solution addresses part of the welding system. Each solution, however, has its advantages and disadvantages, and should be considered in the context of the total system. Likewise, a solution cannot work without proper implementation. The most successful solutions rely on a coordinated effort between managers, engineers, welding supervisors, vendors and especially welders themselves.

Although "fume extraction" may be the first solution that comes to mind, other options should be considered as well. Approaches to controlling welding fume actually fall into two broad categories:

• Reducing fume generation
• Limiting operator exposure to fume

Fume extraction is simply a subset of the second category.

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