Vacuum cleaner

A vacuum cleaner is a device that uses an air pump (a centrifugal fan in all but some of the very oldest models), to create a partial vacuum to suck up dust and dirt, usually from floors, and from other surfaces such as upholstery and draperies. 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—small battery-powered hand-held devices, wheeled canister models for home use, domestic central vacuum cleaners, huge stationary industrial appliances that can handle several hundred litres of dust before being emptied, and self-propelled vacuum trucks for recovery of large spills or removal of contaminated soil. Specialized shop vacuums can be used to suck up both dust and liquids.

Name

Although "vacuum cleaner" is a neutral name, in some countries (UK, Ireland) "hoover" is used instead as a genericized trademark, after one of the first and more influential companies in the development of the device, but actually irrespective of the brand used (like kleenex for facial tissue).

History

The vacuum cleaner evolved from the carpet sweeper via manual vacuum cleaners. The first manual models, using bellows, were developed in the 1860s, and the first motorized designs appeared at the turn of the 20th century, with the first decade being the boom decade.

Manual predecessors

In 1860 a carpet sweeper was invented by Daniel Hess of West Union, Iowa that gathered dust with a rotating brush and a bellows for generating suction.^[1][2] Another early model (1869) was the "Whirlwind", invented in Chicago in 1868 by Ives W. McGaffey. The bulky device worked with a belt driven fan cranked by hand that made it awkward to operate, although it was commercially marketed with mixed success. ^[3] A similar model was constructed by Melville R. Bissell of Grand Rapids, Michigan in 1876.^[4] The company later added portable vacuum cleaners to its line of cleaning tools.

The next improvement came in 1898, when John S. Thurman of St. Louis, Missouri, submitted a patent (US No. 634,042) for a "pneumatic carpet renovator". This was a gasoline powered cleaner although the dust was blown into a receptacle rather than being sucked in, as in the machine now used.^[5] In a newspaper advertisement from the St. Louis Dispatch, Thurman offered his invention of the horse-drawn (which went door to door) motorized cleaning system in St. Louis. He offered cleaning services at $4 per visit. By 1906 Thurman was offering built-in central cleaning systems that used compressed air, yet featured no dust collection. In later patent litigation, Judge Augustus Hand ruled that Thurman "does not appear to have attempted to design a vacuum cleaner, or to have understood the process of vacuum cleaning".^[6]

Vacuum cleaner

The motorized vacuum cleaner was invented by Hubert Cecil Booth of England in 1901.^[5] As Booth recalled decades later, that year he attended "a demonstration of an American machine by its inventor" at the Empire Music Hall in London. The inventor is not named, but Booth's description of the machine conforms fairly closely to Thurman's design, as modified in later patents. Booth watched a demonstration of the device, which blew dust off the chairs, and thought that "...if the system could be reversed, and a filter inserted between the suction apparatus and the outside air, whereby the dust would be retained in a receptacle, the real solution of the hygienic removal of dust would be obtained."^[7] He tested the idea by laying a handkerchief on the seat of a restaurant chair, putting his mouth to the handkerchief, and then trying to suck up as much dust as he could onto the handkerchief. Upon seeing the dust and dirt collected on the underside of the handkerchief, he realized the idea could work.

Booth created a large device,^[8] driven by an internal combustion engine. Nicknamed the "Puffing Billy",^[9] Booth's first petrol-powered, horse-drawn vacuum cleaner relied upon air drawn by a piston pump through a cloth filter. It did not contain any brushes; all the cleaning was done by suction through long tubes with nozzles on the ends. Although the machine was too bulky to be brought into the building, its principles of operation were essentially the same as the vacuum cleaners of today. He followed this up with an electric-powered model, but both designs were extremely bulky, and had to be transported by horse and carriage. The term "vacuum cleaner" was first used by the company set up to market Booth's invention, in its first issued prospectus of 1901.^[7]

Booth initially did not attempt to sell his machine, but rather sold cleaning services. The vans of the British Vacuum Cleaner Company (BVCC) were bright red; uniformed operators would haul hose off the van and route it through the windows of a building to reach all the rooms inside. Booth was harassed by complaints about the noise of his vacuum machines and was even fined for frightening horses. Gaining the royal seal of approval, Booth's motorized vacuum cleaner was used to clean the carpets of Westminster Abbey prior to Edward VII's coronation in 1901.^[10] The device was used by the Royal Navy to improve the level of sanitation in the naval barracks. It was also used in businesses such as theatres and shops, although the device was too large to be feasibly used as a domestic appliance.^[11]

Booth received his first patents on 18 February and 30 August 1901.^[5][12] Booth started the BVCC and refined his invention over the next several decades. Though his "Goblin" model lost out to competition from Hoover in the household vacuum market, his company successfully turned its focus to the industrial market, building ever-larger models for factories and warehouses. Booth's company, now BVC, lives on today as a unit of pneumatic tube system maker Quirepace Ltd.^[13]

The American industry was established by the New Jersey inventor David T. Kenney between 1903 and 1913. Membership in the Vacuum Cleaner Manufacturers' Association, formed in 1919, was limited to licensees under his patents.

Domestic vacuum cleaner

The first vacuum-cleaning device to be portable and marketed at the domestic market was built in 1905 by Walter Griffiths, a manufacturer in Birmingham, England.^[14] His Griffith's Improved Vacuum Apparatus for Removing Dust from Carpets resembled modern-day cleaners; – it was portable, easy to store, and powered by "any one person (such as the ordinary domestic servant)", who would have the task of compressing a bellows-like contraption to suck up dust through a removable, flexible pipe, to which a variety of shaped nozzles could be attached.

In 1906 James B. Kirby developed his first of many vacuums called the "Domestic Cyclone" It used water for dirt separation. He held over 60 patents on everything from a wringerless washing machine to ironing and dry cleaning equipment.

In 1907 department store janitor James Murray Spangler (1848-1915) of Canton, Ohio invented the first portable electric vacuum cleaner,^[10] obtaining a patent for the Electric Suction Sweeper on June 2, 1908. Crucially, in addition to suction from an electric fan that blew the dirt and dust into a soap box and one of his wife's pillow cases, Spangler's design utilized a rotating brush to loosen debris. Unable to produce the design himself due to lack of funding, he sold the patent in 1908 to local leather goods manufacturer William Henry Hoover (1849-1932), who had Spangler's machine redesigned with a steel casing, casters, and attachments, founding the company that in 1922 was renamed the Hoover Company. Their first vacuum was the 1908 Model O, which sold for $60. Subsequent innovations included the beater bar in 1919 ("It beats as it sweeps as it cleans"), disposal filter bags in the 1920s, and an upright vacuum cleaner in 1926.

In Continental Europe, the Fisker and Nielsen company in Denmark was the first to sell vacuum cleaners in 1910. The design weighed just 17.5 kg and could be operated by a single person.

The Swedish company Electrolux launched the innovative Model V in 1921 that was designed to lie on the floor on two thin metal runners. This innovation, conceived by Electrolux founder Axel Wenner-Gren, became a standard feature on generations of future vacuum cleaners. There is a recorded example of a 1930s Electrolux vacuum cleaner surviving in use for over 70 years, finally breaking in 2008.^[15]

Post-Second World War

For many years after their introduction, vacuum cleaners remained a luxury item, but after the Second World War, they became common among the middle classes. Vacuums tend to be more common in Western countries because in most other parts of the world, wall-to-wall carpeting is uncommon and homes have tile or hardwood floors, which are easily swept, wiped or mopped manually without power assist.

The last decades of the 20th century saw the more widespread use of technologies developed earlier, including filterless cyclonic dirt separation, central vacuum systems and rechargeable hand-held vacuums. In addition, miniaturized computer technology and improved batteries allowed the development of a new type of machine — the autonomous robotic vacuum cleaner. In 1997 Electrolux of Sweden demonstrated the Electrolux Trilobite, the first autonomous cordless robotic vacuum cleaner on the BBC-TV program Tomorrow' World, introducing it to the consumer market in 2001.

Recent developments

In 2004 a British company released Airider, a hovering vacuum cleaner that floats on a cushion of air. It has claimed to be light-weight and easier to maneuver (compared to using wheels), although it is not the first vacuum cleaner to do this — the Hoover Constellation predated it by at least 35 years.

A British inventor has developed a new cleaning technology known as Air Recycling Technology, which, instead of using a vacuum, uses an air stream to collect dust from the carpet.^[16] This technology was tested by the Market Transformation Programme (MTP) and shown to be more energy-efficient than the vacuum method.^[17] Although working prototypes exist, Air Recycling Technology is not currently used in any production cleaner.

Modern configurations

A wide variety of technologies, designs, and configurations are available for both domestic and commercial cleaning jobs.

Upright

Upright vacuum cleaners are popular in the United States, Britain and numerous Commonwealth countries, but very unusual in Continental Europe . They take the form of a cleaning head, onto which a handle and bag are attached. Upright designs generally 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-air/direct fan (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 effective 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 as direct-fan cleaners to achieve the same results.

The most 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.

Canister

Canister models (in the UK also often called 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 the user 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 containing 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.

Drum

Drum or shop vac models are essentially heavy-duty industrial versions of cylinder vacuum cleaners, where the canister consists of a large vertically positioned drum which can be stationary or on wheels. Smaller versions, for use in garages or small workshops, are usually electrically powered. Larger models, which can store over 200 litres (53 US gallons), are often hooked up to compressed air, utilizing the Venturi effect to produce a partial vacuum. Built-in dust collection systems are also used in many workshops.

Wet/dry

Wet or wet/dry vacuum cleaners (commonly known by the generic trademark Shop-Vac) are a specialized form of the cylinder/drum models that can be used to clean up wet or liquid spills. They are generally designed to be used both indoors and outdoors and to accommodate both wet and dry debris; some are also equipped with an exhaust port or detachable blower for reversing the airflow, a useful function for everything from clearing a clogged hose to blowing dust into a corner for easy collection.

Pneumatic

Pneumatic or pneumatic wet/dry vacuum cleaners are a specialized form of wet/dry models that hook up to compressed air. They commonly can accommodate both wet and dry soilage, a useful feature in industrial plants and manufacturing facilities.

Backpack

Backpack vacuum cleaners are commonly used for commercial cleaning: they allow the user to move rapidly about a large area. They are essentially small canister vacuums strapped onto the user's back.

Hand-held

Lightweight hand-held vacuum cleaners, either powered from rechargeable batteries or mains power, are also popular for cleaning up smaller spills. Frequently seen examples include the Black & Decker DustBuster, which was introduced in 1979, and numerous handheld models by Dirt Devil, which were first introduced in 1984. Some battery-powered handheld vacuums are wet/dry rated; the appliance must be partially disassembled and cleaned after picking up wet materials, to avoid developing unpleasant odors.

Robotic

In the late 1990s and early 2000s, several companies developed robotic vacuum cleaners, a form of carpet sweeper usually equipped with limited suction power. Some prominent brands are Roomba, Neato, and bObsweep. These machines move autonomously while collecting surface dust and debris into a dustbin. They can usually navigate around furniture and come back to a docking station to charge their batteries, and a few are able to empty their dust containers into the dock as well. Most models are equipped with motorized brushes and a vacuum motor to collect dust and debris. While most robotic vacuum cleaners are designed for home use, some models are appropriate for operation in offices, hotels, hospitals, etc.

The Dyson robotic vacuum cleaner (DC06) was too expensive for home use, due to its high technical specifications. Thus, it was never released, although it is claimed that it would have been the first robotic vacuum cleaner sold.^[19]

In December 2009, Neato Robotics launched the world's first robotic vacuum cleaner which uses a rotating laser-based range-finder (a form of lidar) to scan and map its surrounding. It uses this map to clean the floor methodically, even if it requires the robot to return to its base multiple times to recharge itself. In many cases it will notice when an area of the floor that was previously inaccessible becomes reachable, such as when a dog wakes up from a nap, and return to vacuum that area. It also has the strongest impeller among robotic vacuum cleaners, pulling in 35CFM of air.^[20]

Cyclonic

Portable vacuum cleaners working on the cyclonic separation principle became popular in the 1990s. This dirt separation principle was well known and often used in central vacuum systems. Cleveland's P.A. Geier Company had obtained a patent on a cyclonic vacuum cleaner as early as 1928, which was later sold to Health-Mor in 1939, introducing the Filter Queen cyclonic canister vacuum cleaner.^[21]

In 1979, James Dyson introduced a portable unit with cyclonic separation, adapting this design from industrial saw mills.^[22] He launched his cyclone cleaner first in Japan in the 1980s at a cost of about US$1800 and in 1993 released the Dyson DC01 upright in the UK for £200. Critics expected that people would not buy a vacuum cleaner at twice the price of a conventional unit, but the Dyson design later became the most popular cleaner in the UK.^[23][24]

Cyclonic cleaners do not use filtration bags. Instead, the dust is separated in a detachable cylindrical collection vessel or bin. Air and dust are sucked at high speed into the collection vessel at a direction tangential to the vessel wall, creating a fast-spinning vortex. The dust particles and other debris move to the outside of the vessel by centrifugal force, where they fall due to gravity.

In fixed-installation central vacuum cleaners, the cleaned air may be exhausted directly outside without need for further filtration. A well-designed cyclonic filtration system loses suction power due to airflow restriction only when the collection vessel is almost full. This is in marked contrast to filter bag systems, which lose suction when pores in the filter become clogged as dirt and dust are collected.

In portable cyclonic models, the cleaned air from the center of the vortex is expelled from the machine after passing through a number of successively finer filters at the top of the container. The first filter is intended to trap particles which could damage the subsequent filters that remove fine dust particles. The filters must regularly be cleaned or replaced to ensure that the machine continues to perform efficiently.

Since Dyson's success in raising public awareness of cyclonic separation, several other companies have introduced cyclone models. Competing manufacturers include Hoover, Bissell, Shark, Eureka, Electrolux, Filter Queen, etc., and the cheapest models are no more expensive than a conventional cleaner.

Central

Central vacuum cleaners, also known as built-in or ducted, are a type of canister/cylinder model which has the motor and dirt filtration unit located in a central location in a building, and connected by pipes to fixed vacuum inlets installed throughout the building. Only the hose and cleaning head need be carried from room to room, and the hose is commonly 8 m (25 ft) long, allowing a large range of movement without changing vacuum inlets. Plastic or metal piping connects the inlets to the central unit. The vacuum head may be unpowered, or have beaters operated by an electric motor or by an air-driven turbine.

The dirt bag or collection bin in a central vacuum system is usually so large that emptying or changing needs to be done less often, perhaps a few times per year for an ordinary household. The central unit usually stays in stand-by, and is turned on by a switch on the handle of the hose. Alternately, the unit powers up when the hose is plugged into the wall inlet, when the metal hose connector makes contact with two prongs in the wall inlet and control current is transmitted through low voltage wires to the main unit.

A central vacuum typically produces greater suction than common portable vacuum cleaners because a larger fan and more powerful motor can be used when they are not required to be portable. A cyclonic separation system, if used, does not lose suction as the collection container fills up, until the container is nearly full. This is in marked contrast to filter-bag designs, which start losing suction immediately as pores in the filter become clogged by accumulated dirt and dust.

A benefit to allergy sufferers is that unlike a standard vacuum cleaner, which must blow some of the dirt collected back into the room being cleaned (no matter how efficient its filtration), a central vacuum removes all the dirt collected to the central unit. Since this central unit is usually located outside the living area, no dust is recirculated back into the room being cleaned. Also it is possible on most newer models to vent the exhaust entirely outside, even with the unit inside the living quarters.

Another benefit of the central vacuum is, because of the remote location of the motor unit, there is much less noise in the room being cleaned than with a standard vacuum cleaner.

Constellation

The Hoover Company marketed an unusual vacuum cleaner, called the Constellation, in the 1960s. The cylinder type lacked wheels, and instead the vacuum cleaner floated on its exhaust, operating as a hovercraft, although this is not true of the earliest models. They had a rotating hose with the intention being that the user would place the unit in the center of the room, and work around the cleaner. Introduced in 1954, they are collectible, and are easily identified by their spherical shape. But they remain an interesting machine; restored, they work well in homes with lots of hardwood floors.

The Constellations were changed and updated over the years until discontinued in 1975. These Constellations route all of the exhaust under the vacuum using a different airfoil. The updated design is quiet even by modern standards, particularly on carpet as it muffles the sound. These models float on carpet or bare floor—although on hard flooring, the exhaust air tends to scatter any fluff or debris around.

Hoover re-released an updated version of this later model Constellation in the US (model # S3341 in Pearl White and # S3345 in stainless steel). Changes include a HEPA filtration bag, a 12-amp motor, a turbine-powered brush roll, and a redesigned version of the handle. This same model was marketed in the UK under the Maytag brand as the Satellite because of licensing restrictions. It was sold from 2006 to 2009.

Vehicles

See vacuum truck for very big vacuum cleaners mounted on vehicles.

Other

Some other vacuum cleaners include an electric mop in the same machine: for a dry and a later wet clean.

The iRobot company developed the Scooba, a robotic wet vacuum cleaner that carries its own cleaning solution, applies it and scrubs the floor, and vacuums the dirty water into a collection tank.

Technology

A vacuum's suction is caused by a difference in air pressure. A fan driven by an electric motor (often a universal motor) reduces the pressure inside the machine. Atmospheric pressure then pushes the air through the carpet and into the nozzle, and so the dust is literally pushed into the bag.

Tests have shown that vacuuming can kill 100% of young fleas and 96% of adult fleas.^[25]

Exhaust filtration

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 respirable dust, which is also redeposited into the area being cleaned. There are several methods manufacturers use to control this problem, some of which may be combined together in a single appliance. Typically a filter is positioned so that the incoming air passes through it before it reaches the motor, and then the filtered air passes through the motor for cooling purposes. Some other designs use a completely separate air intake for cooling.

It is nearly impossible for a practical air filter to completely remove all ultrafine particles from a dirt-laden airstream. An ultra-efficient air filter will immediately clog up and become ineffective during everyday use, and practical filters are a compromise between filtering effectiveness and restriction of airflow. One way to sidestep this problem is to exhaust partially filtered air to the outdoors, which is a design feature of some central vacuum systems. Specially engineered portable vacuums may also utilize this design, but are more awkward to set up and use, requiring temporary installation of a separate exhaust hose to an exterior window.

• Bag: The most common method to capture the debris vacuumed up involves a paper or fabric bag that allows air to pass through, but attempts to trap most of the dust and debris. 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 a removable container and a reusable filter, equivalent to a reusable fabric bag.
• Cyclonic separation: A vacuum cleaner employing this method is also bagless. It causes intake air to be cycled or spun so fast that most of the dust is forced out of the air and falls into a collection 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), a water filtration vacuum cleaner uses a water bath as a filter. It forces the dirt-laden intake air to pass through water before it is exhausted, so that wet dust cannot become airborne. The water trap filtration and low speed may also allow the user to use the machine as a stand-alone air purifier and humidifier unit. The dirty water must be dumped out and the appliance must be cleaned after each use, to avoid growth of bacteria and mold, causing unpleasant odors.
• Ultra fine air filter: Also called HEPA filtered, this method is used as a secondary filter after the air has passed through the rest of the machine. It is meant to remove any remaining dust that could harm the operator. Some vacuum cleaners also use an activated charcoal filter to remove odors.

Ordinary vacuum cleaners should never be used to clean up asbestos fibers, even if fitted with a HEPA filter. Specially-designed machines are required to safely clean up asbestos.^[26]

Attachments

Most vacuum cleaners are supplied with numerous specialized attachments, such as tools, brushes and extension wands, which allow them to reach otherwise inaccessible places or to be used for cleaning a variety of surfaces. The most common of these tools are:

• Hard floor brush (for non-upright designs)
• Powered floor nozzle (for canister designs)
• Dusting brush
• Crevice tool
• Upholstery nozzle

Specifications

The performance of a vacuum cleaner can be measured by several parameters:

• Airflow, in litres per second [l/s] or cubic feet per minute (CFM or ft³/min)
• Air speed, in metres per second [m/s] or miles per hour [mph]
• Suction, vacuum, or water lift, in pascals [Pa] or inches of water

Other specifications of a vacuum cleaner are:

• Weight, in kilograms [kg] or pounds [lb]
• Noise, in decibels [dB]
• Power cord length and hose length (as applicable)

Suction

The suction is the maximum pressure difference that the pump can create. For example, a typical domestic model has a suction of about negative 20 kPa. This means that it can lower the pressure inside the hose from normal atmospheric pressure (about 100 kPa) by 20 kPa. The higher the suction rating, the more powerful the cleaner. One inch of water is equivalent to about 249 Pa; hence, the typical suction is 80 inches (2,000 mm) of water.

Input power

The power consumption of a vacuum cleaner, in watts, is often the only figure stated. Many North American vacuum manufacturers give the current only in amperes (e.g. "6 amps"), and the consumer is left to multiply that by the line voltage of 120 volts to get the approximate power ratings in watts. The rated input power does not indicate the effectiveness of the cleaner, only how much electricity it consumes.

After 1 September 2014, due to EU rules, manufacture of vacuum cleaners with a power consumption greater than 1600 watts will be banned, and from 2017 no vacuum cleaner with a wattage greater than 900 watts will be permitted.^[27]

Output power

The amount of input power that is converted into airflow at the end of the cleaning hose is sometimes stated, and is measured in airwatts: the measurement units are simply watts. The word "air" is used to clarify that this is output power, not input electrical power.

The airwatt is derived from English units. ASTM International defines the airwatt as 0.117354 × F × S, where F is the rate of air flow in ft³/min and S is the pressure in inches of water. This makes one airwatt equal to 0.9983 watts.^[28]

See also

References

Further reading

• Booth, H. Cecil "The origin of the vacuum cleaner," Transactions of the Newcomen Society, 1934–1935, Volume 15.
• Gantz, Carroll. The Vacuum Cleaner: A History (McFarland, 2012), 230 pp

External links

Look up vacuum cleaner in Wiktionary, the free dictionary.

Wikimedia Commons has media related to Vacuum cleaner.

Wikisource has the text of the 1911 Encyclopædia Britannica article Vacuum-cleaner.

Vacuum cleaner at DMOZ

• How Stuff Works – Vacuum Cleaner
• HEPA & ULPA vacuum cleaners – what they can and can’t do for IAQ
• Invention of the vacuum cleaner, by H Cecil Booth (excerpt) at the Wayback Machine (archived 20 February 2008)
• The Historyscoper - online course on vacuum cleaner history with reference hyperlinks

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