MetFab - Welding Fume Handbook - Flipbook - Page 4
1 Introduction
Welding, and other hot processes
such as flame and plasma cutting and
spraying, generates fume that can be
harmful to health. Air pollution from
welding has two main constituents:
particulate fume and pollutant gases.
Both can be hazardous to health
when inhaled, but they have different
characteristics and so are treated
separately here.
toxicity of fumes generated include
the material being welded, the welding
process and the welding parameters,
especially current and voltage. The need
to maximise welding productivity and
minimise costs means that many of
these parameters may be fixed, and it is
unfortunate that the most productive
welding techniques often create the
most pollutants.
Most countries have specific health and
safety regulations to reduce and control
people's exposure to welding emissions.
These regulations are generally based
on the airborne concentrations below
which the health hazards from the
substances in question are considered
to be acceptable. These exposure limits
may be measured in ppm, mg/m³ or
other units, they may be averaged over
a reference period or given as maximum
acceptable concentrations, and they
have different names in different
countries - but the goal of keeping
exposure within safe limits is common.
However, with an understanding of
how fumes are generated it is often
possible to reduce pollution without
affecting productivity, even when the
material to be welded and the welding
process are fixed. To control toxic gases,
especially carbon monoxide and ozone,
the choice of shielding gas can be
important. To reduce particulate fume,
the most important parameter is the
choice of consumable.
How easy it is to keep below the
exposure limits depends on the
chemical species present, their
concentrations and the duration of
exposure. The most stringent controls
are needed for emissions containing
high concentrations of components
with low exposure limits.
The best ways to control fume are to
generate less of them, and to change
their composition to make them less
toxic. Secondary methods of control
include fume extraction systems and
personal protective equipment.
Factors affecting the amount and the
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