Abstract: The invention relates to a method of decreasing the risk of injury from mercury in conjunction with dental treatment. The invention is characterized by passing an effective air flow immediately outside the oral cavity in which the dental treatment is effected. The air flow, together with air removed by suction from the oral cavity when sucking saliva therefrom is passed through a first filter in which solid and liquid particles are extracted from the air flow. The air is then passed through a second filter which is capable of taking up essentially all of the mercury vapor present in the air. This filter is preferably a selenium filter.

Abstract: The invention relates to a method for controlling or monitoring the quality of copper cathodes. The method is characterized by stacking cathodes to form a bundle, preferably comprising 10-20 cathodes, and by determining the bulk density, or a value related thereto, of the bundle. The bulk volume or mean height of a cathode bundle can be used with great accuracy. Advantageously, the height of each cathode bundle is measured by means of distance-sensing means of the laser or ultrasonic type placed above the movement path of a cathode bundle.