There are two principal mechanisms by which activated carbon removes contaminants from water; absorption, and catalytic reduction, a process involving the attraction of negatively-charged contaminant ions to the positively-charged activated carbon. Organic compounds are removed by absorption and residual disinfectants such as chlorine and chloramines are removed by catalytic reduction.Activated carbon filters remove/reduce many volatile organic chemicals (VOC), pesticides and herbicides, as well as chlorine, benzene, trihalomethane (THM) compounds, radon, solvents and hundreds of other man-made chemicals found in tap water. They are moderately effective at removing some, but not all, heavy metals. In addition, they can mechanically remove particles down to 0.5 micron, including Giardia and Cryptosporidium, turbidity and particulates. In addition, they also help in removing some iron, manganese, and hydrogen sulfide.