MetFab - Welding Fume Handbook - Flipbook - Page 5
2 Particulate fume
2.1 Formation/Composition
Particulate fume is formed mainly by
the vaporisation of metals and flux. As it
cools, the vapour condenses and reacts
with atmospheric oxygen to form fine
particles consisting mostly of oxides.
Flux
Fumes
Core wire
Vapour Condenstaion
with oxidation
Slag
Deposited metal
Arc
Base metal
Figure 1:
Fume generation during MMA welding
Fume
Respirable
Dusts
The aerodynamic diameter of welding
fume particles is typically 0.01-0.1 µm
at source. By the time the particles
reach the welder's breathing zone
agglomeration has occurred, creating
fume particles in which the size range
1-2 µm predominates.
The size of the particles is important
because it controls the depth to which
they penetrate the respiratory system
and hence their potential to do harm.
Atmospheric dust
Welding and fume dust
Tobacco smoke
Coal dust
Cement dust
Pollen
I
I
0.0001 0.001
I
0.01
I
0.1
I
1.0
I
10
I
100
I
I
1000 10000
Figure 2: Particle sizes (natural and industrial)
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