Chair

When English-speaking philosophers talk about the material world as opposed to ideas, their phrase is tables and chairs. Some diver training organizations and groups of divers teach techniques, such as DIR diving for configuring diving equipment. Activities that are likely to be made insignificant or undone by some future event are said to be like rearranging the deckchairs on the Titanic. An excess of tubes and connections passing through the water tend to decrease diving performance by causing hydrodynamic drag in swimming. If you nearly fell off your chair, it was because you were very surprised. High capacity buoyancy compensators are used to allow the diver to control his or her depth. A movie or a story is said to keep you on the edge of your chair, if it is suspenseful and engaging. When the diver carries many diving cylinders, especially those made of steel, lack of buoyancy becomes a problem.

They are counter-weighted so as to not slide off the arms under the weight of the remote control. The heaviest cylinders are generally carried on the back supported from a backplate while others are side slung from strong points on the backplate. Remote control bags can be draped over the arm of easy chairs or sofas and used to hold remote controls. In technical diving, the diver may carry different equipment for different phases of the dive; some breathing gas mixes may only be used at depth, such as trimix and others, such as pure oxygen, which only may be used during decompression stops in shallow water. They come in various shapes, some specifically sized to fit partially under a desk. Rebreather divers often carry a side-slung open-circuit "bail out" to be used in the event the rebreather fails. This allows chairs on wheels to roll easily over the carpet and it protects the carpet. For open-circuit divers, the two most common types of redundant configurations are the "twinset", consisting of two similar systems, and the "main plus pony", consisting of a large main gas source and a small "pony" set.

Chair mats are plastic mats meant to cover carpet. The diver may carry two or more sets of breathing equipment to provide redundant alternative gas systems in the event that the other fails or is exhausted. Car seats sometimes have built-in and adjustable lumbar supports. They often have their own demand regulators and mouthpieces, and if so, they are technically distinct extra scuba sets. Obus Forme is a major brand in this category and helped develop this market niche. If these extra cylinders are small, they are sometimes called "pony cylinders". Orthopedic backrests provide support for the back. Some scuba sets incorporate attached extra stage cylinders, as bailout in case the main breathing gas supply is used up or malfunctions, or containing another gas mixture.

In cars, they may be used to increase the height of the driver. Many modern rebreathers use advanced electronics to monitor and regulate the composition of the breathing gas. Some are decorative. These systems use small nylon bags of lead shot pellets which are distributed throughout the BCD, allowing a diver to gain a better overall weight distribution leading to a more horizontal position in the water. Chair pads are cushions for chairs. While weighting systems originally consisted of solid lead blocks attached to a belt around the diver's waist, modern diving weighting systems are now incorporated into the BCD. In the second half of 20th century, some people used custom clear plastic covers for expensive sofas and chairs to protect them. Diving weighting systems, ranging from 2 to 15 kilograms, increase density of the scuba diver to compensate for the buoyancy of diving equipment, allowing the diver to fully submerge underwater with ease by obtaining neutral or slightly negative buoyancy.

Covers for sofas and couches are also available for homes with small children and pets. Certain BCD's allow for integrated weight, meaning that the BCD has special pockets for the weights that can be dumped easily in case of an emergency. The chair covers may come with decorative chair ties, a ribbon to be tied as a bow behind the chair. Another button deflates the BCD and increases the density of the equipment and causes the diver to sink. They are typically rented for formal events such as wedding receptions to increase the attractiveness of the chairs and decor. The bladders inside the BCD inflate with air from the ‘direct feed’ to decrease the total density of the SCUBA equipment and cause the diver to float. A chair cover is a temporary fabric cover for a side chair. Although strictly speaking this is not a part of the breathing apparatus, it is usually connected to the divers air supply, in order to provide easy inflation of the device, this can usually also be done manually via a mouthpiece.

If matched to a glider, the ottoman may be mounted on swing arms so that the ottoman rocks back and forth with the main glider. In modern scuba sets, a buoyancy compensator (BC) or buoyancy control device (BCD), such as a back-mounted wing or stabiliser jacket (otherwise known as a 'stab jacket'), is built into the scuba set harness. An ottoman is a short stool to be used as a footrest but can sometimes be used as a stool. The use of an extra feed from the first stage regulator permits control of the life jacket as a buoyancy aid. In place of a built-in footrest, some chairs come with a matching ottoman. The first were inflated with a small carbon dioxide cylinder, later with a small air cylinder. Canada's Canadian General Standards Board CAN/CGSB 44.15M [6] on "Straight Stacking Chair, Steel"). It was put on before putting on the cylinder harness.

Governments will often issue standards for purchases by government agencies (e.g. The ABLJ is used for two purposes, one to adjust the buoyancy of the diver to compensate for loss of buoyancy (chiefly due to compression of neoprene wetsuit) and more importantly as a lifejacket that can be rapidly inflated even at depth. Large institutions that make bulk purchases will reference these standards within their own even more detailed criteria for purchase [5]. In the 1960's adjustable buoyancy life jackets for aqualung-type scuba became available. Under these higher loads, the chair may be damaged, but it must not fail catastrophically. In emergency they had to jettison their weights. The specification further defines heavier "proof" loads that chairs must withstand. In the beginning scuba divers dived without any buoyancy aid.

It specifies things like[4]:. The harnesses of many diving rebreathers made by Siebe Gorman included a large back-sheet of strong reinforced rubber. The Business and Institutional Furniture Manufacturer's Association (BIFMA) defines BIFMA X5.1 for testing of commercial-grade chairs. Sport scuba usually had quick-release fastenings instead of ordinary buckles. ASTM E1822-02b defines the combustibility of chairs when they are stacked. Many did not have a backpack plate, but the cylinders were held directly against the diver's back. ASTM F1858-98 specifies lawn chairs. The buckles were usually quick-release.

ISO 7174 specifies stability of rocking and tilting chairs. Before 1971 all breathing sets including scuba came with a plain harness of straps with buckles like on a rucksack or spray-tank-pack. Bean bag chairs are specified by ANSI standard ASTM F1912-98[3]. Among the things that prompted Cousteau to develop efficient air-breathing diving free-swimming diving gear, were two oxygen toxicity accidents that he had earlier with rebreathers. Dental chairs are specified by ISO 6875. Jacques-Yves Cousteau and Emile Gagnan invented the first type of SCUBA diving equipment, the Aqua-Lung in 1943. There are multiple specific standards for different types of chairs. A predecessor to scuba gear, the Momson lung, was used as emergency escape gear by WWII submariners.

ISO 9241-5:1988[2], "Ergonomic requirements for office work with visual display terminals (VDTs) -- Part 5: Workstation layout and postural requirements " is the most common one for modern chair design. Rebreather technology is also used in space suits. Design considerations for chairs have been codified into standards. Industrial rebreathers have been used since soon after 1900. Open center seats where a soft material is attached to the tops of chair legs or between stretchers to form the seat. The first open-circuit industrial breathing sets were designed by modifying the design of the Cousteau aqualung. Some systems include: Solid center seats where a solid material forms the chair seat. These breathing sets are nowadays called SCBA (Self Contained Breathing Apparatus) (The initials SCBA have had other meanings).

Chair seats vary widely in construction and may or may not match construction of the chair's back. Breathing sets operating on the above principles are not only used underwater but in other situations where the atmosphere is dangerous (little oxygen, poisonous etc). See also seats in movie theaters, and pictures of benches with and without arm rests. There are alternative methods that a person can use to survive and function while underwater, including:. A loveseat in particular, has no arm rest in between. In practice, dive times are more often influenced by other factors such as water temperature and the requirement for safe ascent (see decompression sickness). Arm rests prevent or complicate both desired and undesired proximity. The life of the soda lime scrubber is likely to be less than this and so will be the limiting factor of the dive.

in public transport and other public places, and to prevent lying on the bench or coach. So, a diver who has a 3 litre oxygen cylinder filled to 200 bar and who leaves 25% in reserve will be able to do a 450 minute dive (3 L × 200 bar × 0.75 / 1). The latter may be provided for comfort, but also for privacy e.g. Except during the ascent, the fully-closed circuit rebreather that is operating correctly uses virtually no diluent. A couch, bench, or other arrangement of seats next to each other may have arm rest at the sides and/or arm rests in between. An oxygen rebreather diver consumes about 1 litre of oxygen per minute as does a fully-closed circuit rebreather diver. Hence in some chair designs, the armrest is not continuous to the chair back, but is missing in the elbow area. So, a diver who uses a 5 litre cylinder filled to 200 bar and who leaves 25% in reserve will be able to do a 22.5 minute dive (5 L × 200 bar × 75% / 33.33).

Armrests should support the forearm and not the sensitive elbow area. Although it uses gas more economically, the weight of the rebreathing equipment means the diver carries smaller cylinders. Armrests further have the function of making entry and exit from the chair easier (but from the side it becomes more difficult). Thus, the same diver whose breathing rate at the surface is 25 L/min will consume gas at a rate of about 33.33 L/min. If so, armrests will support part of the body weight through the arms if the arms are resting on the armrests. A semi-closed circuit rebreather dive is about three times the length of the equivalent open circuit dive; gas is recycled but fresh gas must be constantly injected and used gas vented. A chair may or may not have armrests. At 100 L/min the dive will be a maximum of 22.5 minutes (2250/100).

For adjustable chairs, the aforementioned principles are applied in adjusting the chair to the individual occupant. If a 15 litre cylinder filled to 200 bar is used until there is a reserve of 25% there is (75% × 200 × 15) = 2250 litres. In some airplanes and stadiums the seat pitch is so small that there is sometimes there is no leg room for the average person. ( (30 m / 10 m per bar) + 1 bar atmospheric pressure ) × 25 L/min = 100 L/min ). "Seat pitch" is the distance between rows of seats. An open circuit diver whose breathing rate at the surface (atmospheric pressure) is 25 litres per minute will consume 100 litres of gas per minute at 30 metres. The buttock-knee length is used to determine "leg room" between rows of chairs. The duration of an open-circuit dive depends on factors such as the capacity (volume of gas) in the diving cylinder, the depth of the dive and the breathing rate of the diver.

Elbow rest height is used to determine the height of the armrests. Main article :rebreather. Hip breadth is used for chair width and armrest width. The main limiting factors on rebreathers are the duration of the carbon dioxide scrubber, which is generally at least 3 hours, and the efficiency of the scrubber at depth. Additional anthropometric measurements may be relevant to designing a chair. Although oxygen rebreathers have a maximum operating depth of around 6 metres / 18 feet, several types of fully-closed circuit rebreathers, when using a helium based diluent, are capable of 100+ metre / 330+ feet dives. Mass produced chairs are typically 38-43 cm deep. The rebreather's economic use of gas, typically 1.6 litres of oxygen per minute, allows dives of much longer duration than is possible with open circuit equipment where gas consumption is typically 10 times higher.

This anthropometric measurement is used to determine the seat depth. This type of scuba equipment is known as 'closed circuit'. For someone seated, the buttock popliteal length is the horizontal distance from the back most part of the buttocks to the back of the lower leg. Then the gas is fit to be re-inhaled. Mass produced chairs are typically 17 inches high. The oxygen consumed by the diver is replaced, nearly always from a cylinder, The exhaled carbon dioxide generated by the diver is removed by passing the gas through a "scrubber": a canister full of soda lime. The popliteal height, after adjusting for heels, clothing and other issues is used to determine the height of the chair seat. In other rebreathers, the inhaled and exhaled gas goes back and forth along a single tube: this is called the pendulum system.

(The term "sitting height" is reserved for the height to the top of the head when seated.) For American men, the median popliteal height is 16.3 inches and for American women it is 15.0 inches[1]. In some rebreathers, one-way valves direct the gas through a "loop". It is sometimes called the "stool height". With rebreathers, the gas the diver exhales is stored between breaths in a "counterlung". For someone seated, the popliteal height is the distance from the underside of the foot to the underside of the thigh at the knees.
. The two most relevant anthropometric measurement for chair design is the popliteal height and buttock popliteal length. There have been designs for a cryogenic open-circuit scuba which has liquid-air tanks instead of cylinders.

Anthropometric statistics may be gathered for mass produced chairs. Someone made as an experiment a twin-hose type regulator where the energy released as the air expands from cylinder pressure to the surrounding pressure as the diver breathes in, was not thrown away but was used to power a propeller. Individuals may be measured for a custom chair. In comics there have been thousands of drawings of two-cylinder twin-hose aqualungs shown wrongly with one wide breathing tube coming straight out of each cylinder top with no regulator, far more than of twin-hose aqualungs drawn correctly with a regulator. Actual chair dimensions are determined by measurements of the human body or anthropometric measurements. Note its layout in the image. By matching the shape of the occupant's buttocks, weight is distributed and pressure at any given point is reduced. Another optional extra was a mouthpiece that also had a snorkel attached, and a valve to switch between aqualung and snorkel.

A contoured seat pan attempts to distribute weight without padding. These sets came with a mouthpiece as standard, but a fullface mask was an option. Where padding is not desirable, contouring may be used instead. The return tube was not for rebreathing but because the air exhaust needed to be at the same depth as the regulator's second stage diaphragm to avoid pressure differences, which would cause a free-flow or resistance to breathing according to the diver's attitude in the water. For example, in hot climates, padding with fabric or plastic covers is often uncomfortable against the skin. It consists of two wide breathing tubes similar to those on many modern rebreathers. There may be cases where padding is not desirable. In this type of set the two (or occasionally the one or the three) stages of the regulator are in a large circular valve assembly mounted on top of the cylinder pack.

Chairs that have padding that is the same density front and back will feel soft in the back area and hard to the underside of the knees. But when he patented it, the Navy requisitioned the patent, and by the time the Navy found no use in the patent and released it, the market had moved on and he got no use from the patent. Since most of the body weight is supported in the back of the seat, padding there should be firmer than the front of the seat which only has the weight of the legs to support. Captain Trevor Hampton in the 1950's or 1960's designed an early single-hose aqualung with a fullface mask with a circular window which was a very big and thus very sensitive demand regulator diaphragm. In lieu of padding, flexible materials, such as wicker, may be used instead with similar effects of distributing the weight. They made an early make of single-hose aqualung that had a fullface mask as standard. Spreading the area reduces the pressure at any given point. Normalair is a firm that formerly were based at Yeovil (UK).

The same body weight over a smaller area means greater pressure on that area. Many modern scuba sets have a spare second stage demand valve on its own hose, which is called an "octopus" or "alternate air source", which is typically yellow in colour. A hard wood chair feels hard because the contact point between the occupant and the chair is small. This type is called "single hose". However, padding does distribute the weight by increasing the area of contact between the chair and the body. Most modern open-circuit scuba sets have a diving regulator consisting of a first stage pressure reducing valve that is sealed over the diving cylinder's output valve, and the second stage "demand valve"; at the mouthpiece, with a thin pressure hose linking the two stages. Padding will not shift the weight to different parts of the body (unless the chair is so soft that the shape is altered). Colloquially this type of breathing set is often called an aqualung, however, the word Aqua-Lung is correctly a tradename protected by the Cousteau-Gagnan patent.

Padding can be on the seat of the chair only, on the seat and back, or also on any arm rests and/or foot rest the chair may have. The regulator supplies the diver with as much of the gas as needed, at a pressure suitable for breathing at the depth of the diver.
See diving cylinder for more information about the cylinders and how they are arranged.
See Diving regulator for more information about diving regulators. Many chairs are padded or have cushions. This type of set consists of one or more diving cylinders containing breathing gas at high pressure (typically 200-300 Bar) connected to a diving regulator. A sit-stand chair distributes most of the weight of the occupant to the feet. Examples were "Ohgushi's Peerless Respirator", and Commandant le Prieur's breathing sets: see Timeline of underwater technology. A kneeling chair adds an additional body part, the knees, to support the weight of the body. There were attempts at designing and using these before 1939, for diving and for industrial use.

A stool or other simple chair may have a simple straight or curved bar near the bottom for the sitter to place his/her feet on. They run out of air quicker than aqualungs. Some chairs have foot rests. Constant flow scuba sets do not have a demand regulator; the breathing gas flows at a constant rate unless the diver switches it on and off by hand. Reclining chairs typically have at least shoulder height backrests to shift weight to the shoulders instead of just the lower back. Open circuit scuba may supply various breathing gases; but rarely pure oxygen, except during decompression stops in technical diving. Headrests support the head as well and are important in vehicles for preventing "whiplash" neck injuries in rear-end collisions where the head is jerked back suddenly. At partial pressures over about 1.4 to 1.6 atmospheres, oxygen becomes toxic.

Shoulder height backrests support the entire back and shoulders. Newspapers and television news often describe open circuit scuba wrongly as "oxygen" equipment, probably by false analogy from aeroplane pilots' oxygen cylinders. In general, backrests come in three heights: Lower back backrests support only the lumbar region. Some divers use the word "scuba" to mean open-circuit sets only. The back of the chair will support some of the weight of the occupant, reducing the weight on other parts of the body. Some rebreathers only have a constant-flow regulator like in blowtorches. However, reclining may not be suitable for chairs intended for work or eating at table. Most open-circuit scuba and some rebreathers have a demand regulator to control the supply of breathing gas.

In general, if the occupant is suppose to sit for a long time, weight needs to be taken off the seat area and thus "easy" chairs intended for long periods of sitting are generally at least slightly reclined. Both types of scuba provide a means of supplying air or other breathing gas, nearly always from a high pressure diving cylinder, and a harness to strap it to the diver's body. This may be more comfortable for some in reducing weight on the seat area, but may be problematic for others who have bad backs. Modern scuba sets are of two types:. A reclining seat and back will shift weight to the occupant's back. . A lower seat may shift too much weight to the "seat bones" ("ischial tuberosities"). A scuba set provides a scuba diver with the breathing gas necessary to breathe underwater.

It may also result in no weight on the feet which means more weight elsewhere. As with radar, the acronym has become so familiar that it is often not capitalised and is treated as an ordinary word: for example, it has been taken into the Welsh language as "sgwba". A seat that is higher results in dangling feet and increased pressure on the underside of the knees ("popliteal fold"). These initials originated in 1939 in the US Navy to refer to US military diver's rebreather sets. Ergonomic designs distributes the weight of the occupant to various parts of the body. SCUBA is an acronym for Self-Contained Underwater Breathing Apparatus. Easy chairs for watching television or movies are somewhere in between depending on the height of the screen. operations in enclosed or poorly ventilated areas eg large fluid or gas containers,.

Dental chairs are necessarily reclined. mining, especially mine rescue. "Task chairs", or any chair intended for people to work at a desk or table, including dining chairs, can only recline very slightly; otherwise the occupant is too far away from the desk or table. firefighting. Intended usage determines the desired seating position. Snuba Diving - Using the same type of equipment as scuba diving, the diver breathes from compressed air tanks, which float on a free floating raft at the surface, allowing the diver only 20-30 feet (6–9 m) of depth to travel. Chair design considers intended usage, ergonomics (how comfortable it is for the occupant), as well as non-ergonomic functional requirements such as size, stackability, foldability, weight, durability, stain resistance and artistic design. But see Like-A-Fish for an attempt to develop real artificial gills for divers.

. In the real world they would have to process an unrealistically massive amount of water to extract enough oxygen to supply an active diver. See history of the chair for an extended look at chairs from antiquity to the modern day. Artificial gills (human) - these are science fiction only. Headrests for seats in vehicles are important for preventing whiplash injuries to the neck when the vehicle is involved in a rear-end collision. It is memorably portrayed in the film "The Abyss". There may be separate headrests. It has possibilities of being used for very deep diving.

The back may extend above the height of the head. Liquid breathing - so far, in the real world, liquid breathing for humans is only laboratory experiments, and (one lung at a time) medical treatment. Likewise, the back and sometimes the seat are made of porous materials or have holes drilled in them for decoration and ventilation. Atmospheric diving suit - an armored suit which protects the diver from the surrounding water pressure. The back often does not extend all the way to the seat to allow for ventilation. Some tourist resorts now offer a surface supplied diving arrangement, trademarked as Snuba, as an introduction to diving for the inexperienced. Chairs as furniture are typically not attached to the floor and so can be moved. surface supplied diving - originally used in professional diving for long or deep dives where an umbilical line connects the diver with the surface providing breathing gas, and sometimes warm water to heat the diving suit, and usually nowadays voice communications.

A chair mounted in a vehicle or in a theatre is simply called a seat. snorkelling - a form of free-diving where the diver's mouth and nose can remain underwater when breathing, because the diver is able to breathe at the surface through a short tube known as a snorkel. A separate footrest for a chair is known as an ottoman, hassock or poof. free-diving - swimming underwater on a single breath of air. A chair for more than one person is a couch, sofa, settee, loveseat (two-seater without arm rest in between) or bench. SCAMP (Supercritical Air Mobility Pack®) is an out-of-water liquid-air open-circuit breathing set designed by NASA by adapting space suit technology. Without back and arm rests it is called a stool. It would have to be filled immediately before use.

Chairs also often have legs to support the seat raised above the floor. Its diving duration is likely several hours. A chair is a piece of furniture for sitting, consisting of a seat, a back, and sometimes arm rests, commonly for use by one person. Janwillem Bech's rebreather site shows pictures of a Kriolang that was made in 1974. seat cycle strength of 100,000 repetitions of 125 pounds (57 kg) dropped from 2 inches (50 mm) above the seat. The Russian Kriolang (from Greek cryo- (= "frost") + English "lung") was copied from Jordan Klein's "Mako" cryogenic open-circuit scuba. seat strength of 225 pounds (102 kg) dropped from six inches (150 mm) above the seat. Jordan Klein designed a cryogenic open-circuit scuba called "Mako" and made at least a prototype.

leg strength of 75 pounds (34 kg) applied one inch (25 mm) from the bottom of the leg. There are three variants of rebreather: oxygen, semi-closed circuit and fully-closed circuit rebeathers. chair stability if weight is transferred completely to the front or back legs. Rebreathers use gas very economically, making long dives easy and special mixes cheaper to use at the expense of more complicated technology and extensive experience and training requirements. chair backstrength of 150 pounds (68 kg). Here the diver breathes in from the set, and out back into the set where the exhaled gas is reprocessed to make it fit to breathe again. Metal, Metal mesh or wire woven to form seat. closed-circuit (or rebreather).

Splint, ash, oak or hickory strips are woven. Sometimes cave divers have cylinders slung at their sides instead. Caning, woven from rush, reed, rawhide, heavy paper, strong grasses, cattails to form the seat, often in elaborate patterns. Submarine Products sold a sport air scuba with 3 backpack cylinders. Tape, wide fabric tape woven into seat, seen in lawn chairs and some old chairs. "Twin sets" with two backpack cylinders were much more common in the 1960s than now. Fabric, simple covering without support. 21% Oxygen / 79% Nitrogen) The cylinder is nearly always worn on the back.

Leather, may be tooled with a design. Most divers use standard air (i.e. Wicker, woven to provide a surface with give to it. It can be uneconomic when used with expensive gas mixes such as heliox and trimix. Stone, often marble. The duration of open-circuit dives is shorter than a dive with a rebreather, in proportion to the weight and bulk of the set. Molded plastic. This type of equipment is relatively simple, making it cheap and reliable.

Metal seats of solid or open design. Here the diver breathes in from the set and out to waste. Stuffed fabric, similar to padded leather. open-circuit (often called an "aqualung", see Aqua-Lung™). Padded leather, generally a flat wood base covered in padding and contained in soft leather. Wood slats, often seen on outdoor chairs.

Solid wood, may or may not be shaped to human contours.