The device does not use any chemicals but rather resorts to using mechanical filtration. Once entering the apparatus, water passes through a series of fibers with microscopic holes smaller than 0.2 microns wide. In addition, water passes through another layer of ultrafilter, which are even smaller than the microfilters, and an activated carbon filter. The majority contaminants such as bacteria or dirt will get caught in the filters as the clean water passes through and can be safely consumed by the user. A study conducted in Sudan in 2009 found that before using LifeStraw, 16.8% of the 647 participants reported diarrhea in a two week period. After LifeStraws were distributed to participants, only 15.3% reported having diarrhea.