Dyson V15 Detect Cordless Vacuum Cleaner in Grey Brushed Nickel

A cleaner, cleanser or cleaning operative is a type of industrial or domestic worker who is tasked with cleaning a space. A janitor (US and Canada), also known as a custodian, porter or caretaker, is a person who cleans and might also carry out maintenance and security duties. A similar position, but usually with more managerial duties and not including cleaning, is occupied by building superintendents in the United States and Canada and by site managers in schools in the United Kingdom.

According to the Cambridge English dictionary a "cleaner" is "a person whose job is to clean houses, offices, public places, etc.:"; the Collins dictionary states that: "A cleaner is someone who is employed to clean the rooms and furniture inside a building." However, a cleaner does not always have to be employed and perform work for pay, such as in the case of volunteer work or community service. "Cleaner" may also refer to cleaning agents e.g. oven cleaner, or devices used for cleaning, e.g. vacuum cleaner.

Cleaning operatives may specialize in cleaning particular things or places, such as window cleaners, housekeepers, janitors, crime scene cleaners and so on. Cleaning operatives often work when the people who otherwise occupy the space are not around. They may clean offices at night or houses during the workday.

The term cordless is generally used to refer to electrical or electronic devices that are powered by a battery or battery pack and can operate without a power cord or cable attached to an electrical outlet to provide mains power, allowing greater mobility. The term "cordless" should not be confused with the term "wireless", although it often is in common usage, possibly because some cordless devices (e.g., cordless telephones) are also wireless. The term "wireless" generally refers to devices that use some form of energy (e.g., radio waves, infrared, ultrasonic, etc.) to transfer information or commands over a distance without the use of communication wires, regardless of whether the device gets its power from a power cord or a battery. The term "portable" is an even more general term and, when referring to electrical and electronic devices, usually means devices which are totally self-contained (e.g., have built-in power supplies, have no base unit, etc.) and which may also use wireless technology.

Dyson may refer to:

• Dyson (surname), people with the surname Dyson
• Dyson (company), a Singaporean multinational home appliances company founded by James Dyson
• Dyson (crater), a crater on the Moon
• Dyson (operating system), a Unix general-purpose operating system derived from Debian using the illumos kernel, libc, and SMF init system
• Dyson sphere, a hypothetical megastructure that completely encompasses a star and captures most or all of its power output
• Dyson tree, a hypothetical plant suggested by physicist Freeman Dyson
  • Eufloria (formerly called Dyson), a video game based on the idea of Dyson trees
• USS Dyson (DD-572), a United States Navy destroyer in commission from 1942 to 1947
• NOAAS Oscar Dyson (R 224), an American fisheries and oceanographic research ship in commission in the National Oceanic and Atmospheric Administration since 2005
• Dysons, an Australian bus operator
• Dyson, a character in the Canadian television series Lost Girl
• The Charles H. Dyson School of Applied Economics and Management, often referred to as "Dyson"

Grey (more frequent British English) or gray (more frequent American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning that it has no chroma and therefore no hue. It is the color of a cloud-covered sky, of ash, and of lead.

The first recorded use of grey as a color name in the English language was in 700 CE. Grey is the dominant spelling in European and Commonwealth English, while gray is more common in American English; however, both spellings are valid in both varieties of English.

In Europe and North America, surveys show that gray is the color most commonly associated with neutrality, conformity, boredom, uncertainty, old age, indifference, and modesty. Only one percent of respondents chose it as their favorite color.

Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slow to react with air under standard conditions because a passivation layer of nickel oxide forms on the surface that prevents further corrosion. Even so, pure native nickel is found in Earth's crust only in tiny amounts, usually in ultramafic rocks, and in the interiors of larger nickel–iron meteorites that were not exposed to oxygen when outside Earth's atmosphere.

Meteoric nickel is found in combination with iron, a reflection of the origin of those elements as major end products of supernova nucleosynthesis. An iron–nickel mixture is thought to compose Earth's outer and inner cores.

Use of nickel (as natural meteoric nickel–iron alloy) has been traced as far back as 3500 BCE. Nickel was first isolated and classified as an element in 1751 by Axel Fredrik Cronstedt, who initially mistook the ore for a copper mineral, in the cobalt mines of Los, Hälsingland, Sweden. The element's name comes from a mischievous sprite of German miner mythology, Nickel (similar to Old Nick). Nickel minerals can be green, like copper ores, and were known as kupfernickel – Nickel's copper – because they produced no copper.

Although most nickel in the earth's crust exists as oxides, economically more important nickel ores are sulfides, especially pentlandite. Major production sites include the Sudbury region, Canada (which is thought to be of meteoric origin), New Caledonia in the Pacific, Western Australia, and Norilsk, Russia.

Nickel is one of four elements (the others are iron, cobalt, and gadolinium) that are ferromagnetic at about room temperature. Alnico permanent magnets based partly on nickel are of intermediate strength between iron-based permanent magnets and rare-earth magnets. The metal is used chiefly in alloys and corrosion-resistant plating.

About 68% of world production is used in stainless steel. A further 10% is used for nickel-based and copper-based alloys, 9% for plating, 7% for alloy steels, 3% in foundries, and 4% in other applications such as in rechargeable batteries, including those in electric vehicles (EVs). Nickel is widely used in coins, though nickel-plated objects sometimes provoke nickel allergy. As a compound, nickel has a number of niche chemical manufacturing uses, such as a catalyst for hydrogenation, cathodes for rechargeable batteries, pigments and metal surface treatments. Nickel is an essential nutrient for some microorganisms and plants that have enzymes with nickel as an active site.

V15 may refer to:

• Bell XV-15, an American experimental tiltrotor aircraft
• DR Class V 15, a German diesel locomotive
• Laffly V15, a French artillery tractor
• Vanguard 15, an American sailing dinghy
• V15, a grade in bouldering
• V15, other personal history presenting hazards to health, in the ICD-9 V codes
• V-15, a Shure phonograph cartridge

A vacuum (pl.: vacuums or vacua) is space devoid of matter. The word is derived from the Latin adjective vacuus (neuter vacuum) meaning "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often discuss ideal test results that would occur in a perfect vacuum, which they sometimes simply call "vacuum" or free space, and use the term partial vacuum to refer to an actual imperfect vacuum as one might have in a laboratory or in space. In engineering and applied physics on the other hand, vacuum refers to any space in which the pressure is considerably lower than atmospheric pressure. The Latin term in vacuo is used to describe an object that is surrounded by a vacuum.

The quality of a partial vacuum refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum. For example, a typical vacuum cleaner produces enough suction to reduce air pressure by around 20%. But higher-quality vacuums are possible. Ultra-high vacuum chambers, common in chemistry, physics, and engineering, operate below one trillionth (10⁻¹²) of atmospheric pressure (100 nPa), and can reach around 100 particles/cm³. Outer space is an even higher-quality vacuum, with the equivalent of just a few hydrogen atoms per cubic meter on average in intergalactic space.

Vacuum has been a frequent topic of philosophical debate since ancient Greek times, but was not studied empirically until the 17th century. Clemens Timpler (1605) philosophized about the experimental possibility of producing a vacuum in small tubes. Evangelista Torricelli produced the first laboratory vacuum in 1643, and other experimental techniques were developed as a result of his theories of atmospheric pressure. A Torricellian vacuum is created by filling with mercury a tall glass container closed at one end, and then inverting it in a bowl to contain the mercury (see below).

Vacuum became a valuable industrial tool in the 20th century with the introduction of incandescent light bulbs and vacuum tubes, and a wide array of vacuum technologies has since become available. The development of human spaceflight has raised interest in the impact of vacuum on human health, and on life forms in general.