Oral hygiene apparatus for destroying sensitized oral bacteria, comprising: an incoherent light source; and a light directing member, adapted for directing light from said light source onto at least part of a surface of at least one tooth within an oral cavity. The coke oven chambers are kept hot after emptying using externally heated burners, in which a flue gas low in pollutants is obtained from the burners. A switching unit connects a memory with the information processor if the information processor is in the normal power mode, or to the gateway card if the normal power mode of the information processor is changed to the power saving mode. This improves the receiving efficiency when the transmission distance is long and reduces a variation in the received light quantity even if the transmission distance is varied.