MetFab - Welding Fume Handbook - Flipbook - Page 39
10.3 Calculating exposure from emission rates
Figures 28-32 show carbon monoxide in terms of generation
rates, not exposure levels. This is a problem in that it is
difficult to predict exposure levels from emission rates; all
that we can say for certain is that for an identical work
situation, a welding process with a higher carbon monoxide
emission rate will expose the welder to higher concentrations
of the gas.
We can, however, compare measured emission rates and
exposures for certain welding conditions (Figure 33).
I
60
I
40
I
30
I
20
I
10
I
Exposure ml/s
CO exposure standard
50
0
I
2
I
4
I
6
I
8
I
10
I
12
CO emission rate ml/s
Figure 33: The effect of CO emission rate on exposure to carbon
monoxide. Flat welding, open workshop, 33% duty cycle
Figure 33 shows that exposure to carbon monoxide is only
likely to be a problem if the emission rate is above 1Oml/s. In
practice, this means that MAG welding with a carbon dioxide
shielding gas and spray transfer, or FCAW with a carbon
dioxide shielding gas, may present problems with carbon
monoxide.
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