The activated bamboo charcoal is a form of carbon that has been processed at a high temperature level to make it extremely porous to create a large surface area. It also has invisible numerous holes where it looks smooth & solid in the cube. They are excellent at absorbing and trapping harmful substances from the air such as allergens, smoke, odours etc. Chikuno Cube works best in a small enclosed space; refrigerator & closets, up to 1.6sqm It is eco-friendly and can be re-used for up to one year by just exposing it to direct sunlight every month for 6 hours. The quality is rooted in Kyoto's craftsmanship, and it won the Japanese Good Design Award in 2008.