A vacuum cleaner, commonly referred to as a "vacuum" is a device that uses an air pump to create a partial vacuum to suck up dust and dirt, usually from floors, and optionally from other surfaces as well. The dirt is collected by either a dustbag or a cyclone for later disposal. Vacuum cleaners, which are used in homes as well as in industry, exist in a variety of sizes and models.

Upright
Upright vacuum cleaners are common in Britain but very unusual in Continental Europe. They take the form of a cleaning head, onto which a handle and bag are attached. Upright designs usually employ a rotating brushroll or beater bar, which removes dirt through a combination of sweeping and vibration. There are two types of upright vacuums; dirty-fan/direct air (found mostly on commercial vacuums), or clean-air/fan-bypass (found on most of today's domestic vacuums).

The older of the two designs, direct-fan cleaners have a large impeller (fan) mounted close to the suction opening, through which the dirt passes directly, before being blown into a bag. The motor is often cooled by a separate cooling fan. Because of their large-bladed fans, and comparatively short airpaths, direct-fan cleaners create a very efficient airflow from a low amount of power, and make great carpet cleaners. Their "above-floor" cleaning power is less efficient, since the airflow is lost when it passes through a long hose, and the fan has been optimized for airflow volume and not suction.

Fan-bypass uprights have their motor mounted after the filter bag. Dust is removed from the airstream by the bag, and usually a filter, before it passes through the fan. The fans are smaller, and are usually a combination of several moving and stationary turbines working in sequence to boost power. The motor is cooled by the airstream passing through it. Fan-bypass vacuums are good for both carpet and above-floor cleaning, since their suction does not significantly diminish over the distance of a hose, as it does in direct-fan cleaners. However, their air-paths are much less efficient, and can require more than twice as much power than direct-fan cleaners to achieve the same results.

The least common upright vacuum cleaners use a drive-belt powered by the suction motor to rotate the brush-roll. However, a more common design of dual motor upright is available. In these cleaners, the suction is provided via a large motor, while the brushroll is powered by a separate, smaller motor, which does not create any suction. The brush-roll motor can sometimes be switched off, so hard floors can be cleaned without the brush-roll scattering the dirt. It may also have an automatic cut-off feature, which shuts the motor off if the brush-roll becomes jammed, protecting it from damage.

Cylinder

Cylinder models dominate the European market. They have the motor and dust collector (using a bag or bagless) in a separate unit, usually mounted on wheels, which is connected to the vacuum head by a flexible hose. Their main advantage is flexibility, as you can attach different heads for different tasks, and maneuverability (the head can reach under furniture and makes it very easy to vacuum stairs and vertical surfaces. Many cylinder models have power heads, as standard or add-on equipment, which contain the same sort of mechanical beaters as in upright units, making them as efficient on carpets as upright models. Such beaters are driven by a separate electric motor or a turbine which uses the suction power to spin the brushroll via a drive belt.

Vacuums by their nature cause dust to become airborne, by exhausting air that is not completely filtered. This can cause health problems since the operator ends up inhaling this dust. There are several methods manufacturers are using to solve this problem. Some methods may be combined together in a single vacuum. Typically the filter is positioned so that the incoming air passes through it before it reaches the motor. Typically, the filtered air then passes through the motor for cooling purposes.

Bag: The bag is the typical method to capture the debris vacuumed up. It involves a paper or fabric bag that allows air to pass through, but attempts to trap all dust and debris in the bag. The bag may be disposable, or designed to be cleaned and re-used.
Bagless: In non-cyclonic bagless models, the role of the bag is taken by the container and a reusable filter, equivalent to a reusable fabric bag.
Cyclonic separation: Vacuum cleaners employing this method are also bagless. It causes intake air to be cycled or spun so fast that the dust is forced out of the air and falls into a storage bin. The operation is similar to that of a centrifuge.
Water filtration: First seen commercially in the 1920s in the form of the Newcombe Separator (later to become the Rexair Rainbow), water filtration vacuum cleaners use water as a filter. It forces the intake air to pass through water before it is exhausted. The idea behind this is that wet dust cannot become airborne. They require the dirty water to be dumped and the machine rinsed out after every use, to prevent unpleasant odors and mold growth.
Ultra fine air filter: Also called HEPA filtered. This method is used as a secondary filter after the air has passed thought the rest of the machine. It is meant to remove any remaining dust that could harm the operator. Some vacuum cleaners also use a charcoal filter to remove odors.