Specifically for the ME403AF Fume Extraction MIG Torch packages. MIG nozzles or shrouds guide the shielding gas to provide an inert atmosphere for the weldpool and this design ensures the extraction airflow does not suck away the shielding gas.
As always, gas flow is critical as a too low flow entraps air before it reaches the weldpool causing porosity and too much can have the same effect when the speed of the gas is too high and “mechanically” mixes the air into the gas stream causing the porosity.