The hibachi (火鉢) is a traditional Japanese heating device. It is a brazier which is a round, cylindrical, or box-shaped, open-topped container, made from or lined with a heatproof material and designed to hold burning charcoal. It is believed hibachi date back to the Heian period (794 to 1185). It is filled with incombustible ash, and charcoal sits in the center of the ash. To handle the charcoal, a pair of metal chopsticks called hibashi (火箸) is used, in a way similar to Western fire irons or tongs. Hibachi were used for heating, not for cooking. It heats by radiation, and is too weak to warm a whole room. Sometimes, people placed a tetsubin (鉄瓶) over the hibachi to boil water for tea. Later, by the 1900s, some cooking was also done over the hibachi. Traditional Japanese houses were well ventilated (or poorly sealed), so carbon monoxide poisoning or suffocation from carbon dioxide from burning charcoal were of lesser concern. Nevertheless, such risks do exist, and proper handling is necessary to avoid accidents. Hibachi must never be used in airtight rooms such as those in Western buildings. In North America, the term hibachi refers to a small cooking stove heated by charcoal (called a shichirin in Japanese), or to an iron hot plate (called a teppan in Japanese) used in teppanyaki restaurants.