Exposure Factors
Welding fume exposure tends to be highly variable
due to several factors that should be considered
when assessing potential exposures to Cr(VI). Based
on the author’s experience, the primary Cr(VI) exposure
factors are as follows:
•Welding process.As noted, thewelding process
used has a significant effect on FGR.
•Chromium content and flux ingredients in the
consumable. Stainless steel and chromium alloys
typically contain between 11.5%and 30%chromium,
by weight. Obviously, as the chromium content in
the consumable increases, the amount of Cr(VI)
emitted from the welding process will likely
increase. Other ingredients in the electrode alsomay
have some affect in stabilizing Cr(VI), resulting in
higher Cr(VI) concentrations.
•Chromate coatings on basematerial. Chromates
may be contained in pigments in coatings and paints
to provide corrosion-resistant properties. When performing
repair work on painted structures, be sure to
analyze bulk samples of the coating to ensure that the
paint or coating does not contain chromates.
•Welding rate. High welding rates increase the
fumes generated. However, information pertaining
to an individual’s welding or production rate is seldom
accurately and consistently measured when
monitoring exposure. Consider using an arc timer to
accurately collect and document actual welding
time; this information may also prove useful in
explaining unusually high or lowexposuremonitoring
results and/or in better categorizing similar
exposure groups (SEGs).
•Relative welding position. The welding position
plays a significant role in exposure primarily
due to the plume’s path of travel. Welding in a
down-flat position (such as a tank bottom or where
the workpiece is positioned below the welder’s
waist) tends to present the highest potential fume
exposures.Welding in a horizontal direction (such as
when welding the girth seam of a tank) can also create
relatively high fume exposures depending on the
plume’s path of travel in relation to the welder’s
breathing zone.Welding in a vertical direction (such
as a vertical seam of a tank shell) tends to have the
lowest potential fume exposure since the welder’s
breathing zone is typically not in the plume’s travel
path since the plume stays close to the heat-affected
zone as it naturally rises.
•Local exhaust ventilation (LEV). It has been
shown that the use of LEV can lower fume exposure.
However, the effectiveness of LEV depends on several
factors, including work practices and proper
maintenance of the LEV units. (The use of LEV for
fume control is discussed on p. 28.)
•Welding environment (inside or enclosed space).
Welding inside buildings or an enclosed space presents
the potential for an accumulation of fumes that
may increase exposures to the welder as well as to
other personnel inside the building or enclosed space.
•General/dilution ventilation and natural air
currents. Although general/dilution ventilation is