After thinking a bit more I may have been thinking about mass spectrometry, not a clearing technology. May well not be in the slightest bit relevant.
Well, removing soot from a gas sort of is mass spectroscopy, so your idea might work. The problem is getting all those particles charged. As far as I know, the bad efficiency of this kind of mass spectrometers is caused by inefficient ionization, as you cannot get high intensities with an electron beam because of Coulomb repulsion.
What's the velocity of your gas flow? And is there gravity, or are you in space? I'm thinking of some sort of trap, where the gas flows in and kind of circulates around, and the lightest part escapes through the top, the gas, and the soot settles to the bottom.
Anything that involves settling probably requires a reduction in pressure.
Do radio waves become corrupt in space? If some species on a different planet has broadcast radio programs, are we sure to recognize it when the waves reach us?
I can think of three effects that could be a problem:
1) Redshift: As space is expanding, the signal will be shifted to lower frequencies. A lower carrier frequency has less bandwidth, so a densely coded signal might lose information.
2) Attenuation: At large distances, any signal will decrease in intensity with one over the square of the distance. At interstellar distances, you would have to start out with a huge signal so that you can recover a tiny amount of it.
3) Dispersion: Although space is mostly empty, it still has some matter that amounts to a tiny amount of dispersion. If the signal travels long enough through a dispersive medium, it will lose information.
So no, a signal emitted by aliens is not guaranteed to be recognizable when it reaches us. How much a signal is degraded and by what effect is probably specific to the signal and the exact nature of the space in between, so I do not think there is a general answer.