At the same factory the flouring bench was in the same room as the machines, and the locally applied exhaust drew its air-supply from the general atmosphere of the room. Apart from faulty arrangement of the exhaust ducts leading to effects of too local a character, dust was drawn from other parts of the room, including the machines, so much so as to necessitate frequent cleaning of the glass hoods. Poisoning among those employed in flouring occurred. To remedy this, an air-grid with curved inlets at intervals of 2 inches apart, leading into a trunk in connection with a fan, was placed along the back of the bench and under the top of the glass hood. In order, however, that its action should not interfere unduly with the general ventilation of the room, but be, in large measure, independent of this, a somewhat similar grid, introducing air from the street outside, was fitted along the front of the bench. The whole arrangement was operated by one suction fan. Ten cases occurred in this factory in the year before this arrangement was carried out. In the three years since, three cases only have been reported. In the ten years 1900-1909, 48 cases were reported among 257 persons employed. =Vitreous Enamelling[27].=--Surfaces, such as sheet iron for advertisement signs, cast iron for baths and gas stoves, copper for copper letters and tablets, brass for jewellery, and glass for lettering and decoration, are treated with glaze or enamel colours, which, either in the mode of application or subsequent treatment before final vitrefaction, give rise to dust. In the manufacture of advertisement signs, glaze is swilled on to the sheet of iron. After drying, it is fired or vitrified, and upon this surface as many other coats of glaze are applied as may be wanted. As soon as the colour is dry, lettering is effected by brushing away the dried (but not fired) glaze exposed through stencils. _Dangers and Prevention._--Exhaust ventilation for the removal of the dust is essential, but it is, unfortunately, unable to draw the dust away when brushing is done at a distance of more than about 18 inches from the exhaust opening. And some of the plates required are very large. No exhaust-pipe has yet been invented which will follow the hand of the worker without impeding movement. In consequence of severe incidence of poisoning, mainly on young women who do the work of brushing, when the process was first introduced with enamel glazes containing from 15 to 75 per cent. of lead, manufacturers quickly turned their attention to use of enamels free from lead. For this class of work they appear to have been entirely successful, and now lead poisoning is almost a thing of the past. Thus, of 122 samples examined in 1910 from factories claiming exemption from the regulations by reason of the use of enamels containing less than 1 per cent. of lead, excess was found in three only[28].