Carbon filters are very effective at removing a number of deleterious chemicals. These include chlorine, benzene, radon, solvents trihalomethane compounds, volatile organic chemicals such as pesticides and herbicides and hundreds of other man-made chemicals that may come into contact with tap water as it proceeds through the system. In addition, filters remove bad tastes and odors from the water.
Carbon filters are not particularly successful at removing dissolved inorganic contaminants and heavy metals such as minerals, salts, antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, copper, fluoride, mercury, nickel, nitrates, selenium, sulfate, thallium and other contaminants, which may require a reverse osmosis system or distiller instead. Carbon block filters can remove some large, dangerous microorganisms, such as giardia and cryptosporidium, that can cause a number of diseases and epidemics, but nothing less than the size of the carbon itself. Viruses are too small to be removed by carbon, as they usually range between 20 and 400 nanometers in size