=188. Cautions in Using Vacuum Cleaners.= The difficulties to be met with in vacuum cleaners are leaks. First of all, the machine must be fitted together perfectly; if not, the dust drawn into the machine escapes into the air of the room instead of into the collection pan or chamber. Machines are made air-tight, but to be cleaned, they must be taken apart. In putting them together, the housekeeper must take pains to fit them together perfectly. Never neglect to empty the dust chamber. Keep the machine properly oiled. A punctured bellows or a leaky dust strainer will cause dust to escape after being drawn into the machine. These have to be remedied with new parts. Some machines leak because of improper manipulation, such as a too-fast or too-jerky motion in operating them. The directions for each machine tell how to use it--such directions cannot be given here because they differ so much. When the pan has become over-full of dirt, the machine will necessarily throw out dust as well as air. Letting the machine get over-full of dust may ruin the machine by making some part leak continuously. [Illustration: FIG. 99. Electric vacuum cleaner.] =189. Difference Between Hand and Power Cleaners.= Power machines differ from hand ones in that they are run by motor power (Figs. 99 and 99-a). They may have larger collecting chambers and may be stationary in the cellar and connected to the rooms by long pipes (Fig. 100). They must likewise not be over-full of dust. They must be kept properly adjusted. As the operation of the mechanism shakes the machine, it may loosen screws and nuts, so they must be kept tightened. The motor must also be kept in order. The motors used for vacuum cleaners are the same as those used on other power devices. They may be small electric motors, forming a part of the machine, or large motors which operate several machines. In any case, they must be given the same care as any other motor of the same type. (See Chapter XXXVIII.) If they become overheated, they will not work well. They must be kept lubricated to avoid friction, and they must be kept properly adjusted. Fig. 100-a shows a number of different attachments for vacuum cleaners. [Illustration: FIG. 99-_a_. Electric vacuum cleaner, showing parts.] =190. Carpet Sweeper.= A carpet sweeper is a combination of brush and dust pan. The advantage of this device is that the dust is gathered into the machine as the brush rotates, due to the action of the wheels on which the machine moves. The dust is collected into pans at each side of the brush; these are covered so that the dust does not fly into the air as much as otherwise would be the case (Fig. 101). [Illustration: FIG. 100. Stationary vacuum cleaner.] [Illustration: FIG. 100-_a_. Nozzles for vacuum cleaner.] [Illustration: FIG. 101. Section of carpet sweeper.]