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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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