In reply to carrot_boy (North East Wales MC):
Not soda but carbon dioxide. Not as daft as it sounds; Boeing (I think) first developed this for paint stripping aircraft without damaging the substrate.
The pelletised CO2 (ie solid) is propelled by air (as in grit blasting) and tends to penetrate the material to be removed (ie the paint or surface contamination in other situations) then sublimes from solid to gas and the massive increase in volume strips the paint etc from the substrate.
The big advantage of this process is that there is only gas and the stripped material to dispose of, not tonnes of grit, sand, soda or crushed walnut shell (one of the more exotic media that we looked at when developing such systems). Google cryogenic or dry ice blasting fr more info.