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In this posts i want to show about shisha or hookah.

In the Arab world, people smoke it as part of their culture and traditions. Social smoking is done with a single or double hose, and sometimes even more numerous such as a triple or quadruple hose in the forms of parties or small get-togethers. When the smoker is finished, either the hose is placed back on the table signifying that it is available, or it is handed from one user to the next, folded back on itself so that the mouthpiece is not pointing at the recipient. It has been recorded that the Arabs are the biggest shisha smokers in the World and have the most shisha Cafes.^{[citation needed]}

Most cafés (Arabic: مقهىً, transliteration: maqhah, translation: coffeeshop) in the Middle East offer shishas. Cafés are widespread and are amongst the chief social gathering places in the Arab world (akin to public houses in Britain). Some expatriate Britons arriving in the Middle East adopt shisha cafés to make up for the lack of pubs in the region, especially where prohibition is in place.

Shisha Component

Excluding grommets, a hookah is usually made of five or six components, four of which are essential for its operation.

The bowl

Also known as the head of the hookah, the bowl is a container, usually made out of clay or marble, that holds the coal and tobacco during the smoking session. The bowl is loaded with tobacco then covered in a small piece of perforated aluminum foil or a glass or metal screen. Lit coals are then placed on top, which allows the tobacco to heat to the proper temperature.

There is also a variation of the head which employs a fruit rather than the traditional clay bowl. The fruit is hollowed out and perforated in order to achieve the same shape and system a clay bowl has, then it is loaded and used in the same manner.

Windscreen (optional)

A Hookah Cover windscreen is a cover which sits over the bowl area, with some form of air holes. This prevents wind from increasing the burn rate and temperature of the coal, and prevents ash and burning embers from being blown onto the surrounding environment. This may also offer some limited protection from fire as it may prevent the coal from being ejected if the hookah is bumped.

Hose

Technically if the pipe has a hose it is not "hookah"—the term historically referred to a straight-neck tube. Today the hose (one or more) is a slender flexible tube that allows the smoke to be drawn for a distance, cooling down before inhalation. The end is typically fitted with a metal, wooden, or plastic mouthpiece of various shape, size, color or material type.

Body and gaskets

The body of the hookah is a hollow tube. The bowl is attached to the top. Sometimes an ice bucket is attached between the body and the bowl to cool the smoke. At the bottom is a thin tube (the downstem) that is submerged in water. The point where the body meets the water jar is sealed with a gasket. Near there are at least two holes that open into the space above the water. One or more may accept a hose.

Purge valve (optional)

Many hookah are equipped with a purge valve connected to the airspace in the water jar to purge stale smoke which has been sitting unused in the jar for too long. This one-way valve is typically a simple ball bearing sitting over a port which seals the port by gravity alone and will open if positive pressure is created by blowing into the hose. The bearing will be held captive with a screw-on cover. The cover should be opened and the bearing and seat cleaned of residue and corrosion regularly to ensure proper sealing.

Water jar

The body of the hookah sits on top of the water jar. The downstem hangs down below the level of the water in the jar. Smoke passes through the body and out the downstem where it bubbles through the water. This cools and humidifies the smoke. Liquids such as fruit juice may be added to the water or used in substitution. Pieces of fruit, mint leaves, and crushed ice may be added.

Plate

A plate or ashtray sits just below the bowl to catch ashes falling off the coals.

Grommets

Grommets in a hookah are usually placed between the bowl and the body, the body's gasket and the water jar and between the body and the hose. The reason for the usage of grommets although not essential (the use of paper or tape has become common) will help to seal the joints between the parts, therefore decreasing the amount of air coming in and maximizing the smoke breathed in.

Operation

The jar at the bottom of the hookah is filled with water sufficient to submerge a few centimetres of the body tube, which is sealed tightly to it. Deeper water will only increase the inhalation force needed to use it. Tobacco is placed inside the bowl at the top of the hookah and a burning charcoal is placed on top of the tobacco. Some cultures cover the bowl with perforated tin foil or a metal screen to separate the coal and the tobacco, which minimizes inhalation of coal ash with the smoke. This may also reduce the temperature the tobacco is exposed to, in order to prevent burning the tobacco directly.

When one inhales via the hose, air is pulled through the charcoal and into the bowl holding the tobacco. The hot air, heated by the charcoal evaporates (not burns) the tobacco, thus producing smoke, which is passed down through the body tube that extends into the water in the jar. It bubbles up through the water, losing heat, and fills the top part of the jar, to which the hose is attached. When a smoker inhales from the hose, smoke passes into the lungs, and the change in pressure in the jar pulls more air through the charcoal, continuing the process.

If the hookah has been lit and smoked but has not been inhaled for an extended period, the smoke inside the water jar may be regarded as "stale" and undesirable. Stale smoke may be exhausted through the purge valve, if present. This one-way valve is opened by the positive pressure created from gently blowing into the hose. It will not function on a multiple-hose hookah unless all other hoses are plugged. Sometimes one-way valves are put in the hose sockets to avoid the need to manually plug hoses.

Health effects

A common belief among users is that the smoke is significantly less dangerous than that from cigarettes.^[21] The water moisture induced by the hookah makes the smoke less irritating and may give a false sense of security and reduce concerns about true health effects.^[22] Doctors at institutions including the Mayo Clinic have stated that use of hookah is equally detrimental to a person's health as smoking cigarettes,^[23][24] and a study by the World Health Organization also confirmed these findings.^[25]

Each hookah session typically lasts more than 40 minutes, and consists of 50 to 200 inhalations that each range from 0.15 to 0.50 liters of smoke.^[26][27] Reports by the World Health Organization and the American Cancer Society have shown that, in a one-hour hookah session, users consume about 100 to 200 times the smoke and about 70 times the nicotine as they do in one cigarette.^[28]

A study in the Journal of Periodontology found that water pipe smokers were five times more likely than non-smokers to show signs of gum disease. People who smoked water pipes had five times the risk of lung cancer as non-smokers.^[29]

The water used to filter the chemicals does not work efficiently to remove all the harmful chemicals.^[30]

A study on hookah smoking and cancer in Pakistan was published in 2008.^[31] Its objective was "to find serum CEA levels in ever/exclusive hookah smokers, i.e. those who smoked only hookah (no cigarettes, bidis, etc.), prepared between 1 and 4 times a day with a quantity of up to 120 g of a tobacco-molasses mixture each (i.e. the tobacco weight equivalent of up to 60 cigarettes of 1 g each) and consumed in 1 to 8 sessions". Carcinoembryonic antigen (CEA) is a marker found in several forms of cancer. Levels in exclusive hookah smokers were lower compared to cigarette smokers although the difference was not statistically significant between a hookah smoker and a non-smoker. Also the study concluded that heavy hookah smoking (2–4 daily preparations; 3–8 sessions a day ; 2 hrs to 6 hours) substantially raises CEA levels.

Source wikipedia....