An apparatus and method for reducing power consumption in a mobile communication system are provided. The wavelength of the EUV light used in the process is less than 11 nm, for example 6. The invention also relates to chewing gum compositions comprising nicotine, which compositions provide a rapid release of nicotine. The mobile cleaning unit can use cleaning fluid produced at the facility site and return the cleaning fluid to the facility site for reprocessing after the heat exchanger tube bundles are cleaned.