The CO2 Snow Cleaning process removes particles of all sizes, from visible down to 3 – 5 nanometers. At the same time, hydrocarbon-based contamination and organic residues can be removed. Carbon dioxide snow cleaning is nondestructive, nonabrasive, residue-free, and environmentally friendly – there is no chemical waste. The cleaning process is based upon the controlled expansion of either liquid or gaseous carbon dioxide. This expansion leads to the nucleation of small dry ice particles and a high velocity carrier gas stream. Upon impact with a surface, the dry ice removes particles of all sizes by momentum transfer, and hydrocarbons and organics via a transient solvent or a freeze fracture mechanism. The high-velocity gas blows the contaminants away. Additionally, nozzle design changes can be made for cleaning large telescope mirrors.