Abstract: A heating-element accommodating-box cooling apparatus includes: an indoor air passage 5 for fetching air in a heating-element accommodating box and returning it to the heating-element accommodating box; an outdoor air passage 9 for fetching outdoor air and exhausting the fetched outdoor air to the outside; a partition plate 10 provided so that both of the air passages become independent of each other; a fan unit 3 for conveying air in the outdoor air passage 9 and the indoor air passage 5; and a heat exchange element 4 disposed at a point of intersection between the two passages to exchange the sensible heat of the outdoor air and the indoor air, wherein the heating-element accommodating-box cooling apparatus is mounted exteriorly on a panel of the heating-element accommodating box. Consequently, it is possible to effect cooling of the heating-element accommodating box with energy saving, and the space for installation of the cooling apparatus in the box is not required.

Abstract: A control apparatus for a dental gas burner is disclosed which is capable of variably setting combustion time of the burner as desired. The control apparatus comprises a circuit for operating a solenoid valve provided at a fuel gas supply pipe, a circuit for igniting fuel gas ejected from a burner nozzle, a command circuit including a touch sensor and generating a pulse every touch with respect to the touch sensor, a combustion time setting circuit acting to count pulses of the command circuit to set combustion time corresponding to the number of counted pulses to open the valve during the time, and a timing circuit for supplying to the combustion time setting circuit a count signal required for counting the pulses.

Abstract: A method of purifying the contamination of a dental consultation room is disclosed. The purification method is characterized in that an anesthetic gas such as laughing gas and the dust generated by drilling a tooth or false tooth of the patient are changeably sucked either from a region close to the floor of the dental consultation room, or from outside the oral cavity of the patient, and are discharged outside the consultation room. Disclosed also is an apparatus for practicing the purification method.