Activated carbon, or activated charcoal, is a form of carbon perforated with small, shallow pores. These pores increase the surface area available for adsorption or chemical reactions. A gram of activated carbon can have a surface area ranging from 500 m2 to 3,000 m2 — roughly equivalent to the area of a school stadium. It is produced from such source materials as bamboo, coconut husk, willow peat, wood, coir, lignite, coal, and petroleum coke. It is utilized in protective equipment such as gas masks. It can be used to treat various types of food poisoning. It is widely used in the chemical industry as a catalyst. Filters containing activated carbon are utilized in many modern devices used to purify drinking water.