Gas cylinder

For the mechanical devices used to impart a force from a pressurized gas, see pneumatic cylinder. For the large structures used to store town gas, see gas holder.

Industrial compressed gas cylinders used for oxy-fuel welding and cutting of steel.

A gas cylinder is a pressure vessel for storage and containment of gases at above atmospheric pressure. High-pressure gas cylinders are also called bottles. Inside the cylinder the stored contents may be in a state of compressed gas, vapor over liquid, supercritical fluid, or dissolved in a substrate material, depending on the physical characteristics of the contents. A typical gas cylinder design is elongated, standing upright on a flattened bottom end, with the valve and fitting at the top for connecting to the receiving apparatus.

The term cylinder in this context is not to be confused with tank, the latter being an open-top or vented container that stores liquids under gravity, though the term scuba tank is commonly used to refer to a cylinder used for breathing gas supply to an underwater breathing apparatus.

Nomenclature

In the United States, "bottled gas" typically refers to liquefied petroleum gas. "Bottled gas" is sometimes used in medical supply, especially for portable oxygen tanks. Packaged industrial gases are frequently called "cylinder gas", though "bottled gas" is sometimes used. The term propane tank is also used for cylinders with propane.

The United Kingdom and other parts of Europe more commonly refer to "bottled gas" when discussing any usage, whether industrial, medical, or liquefied petroleum. In contrast, what is called liquefied petroleum gas in the United States is known generically in the United Kingdom as "LPG" and it may be ordered by using one of several trade names, or specifically as butane or propane, depending on the required heat output.

The size of a pressurised gas container that may be classed as a gas cylinder is typically 0.5 litres to 150 litres. Smaller containers may be termed gas cartridges, an larger may be termed gas tubes, tanks, or other specic typed of pressure vessel. A gas cylinder is used to store gas or liquified gas at pressures above normal atmospheric pressure.

Gas cylinders may be grouped by several characteristics, such as construction method, material, pressure group, class of contents, transportability, and reusability.

Materials

For a detailed discussion about the materials for gas cylinders, see Pressure vessel § Construction materials.

Design codes and application standards and the cost of materials dictated the choice of steel with no welds for most gas cylinders; the steel is treated to resist corrosion. Some newly developed lightweight gas cylinders are made from stainless steel and composite materials. Due to the very high tensile strength of carbon fiber reinforced polymer, these vessels can be very light, but are more difficult to manufacture.

Cylinders reinforced or built-up with a fibre material usually must be inspected more frequently than metal cylinders, e.g., every 5 instead of 10 years, and must be inspected more thoroughly than metal cylinders. They may have a limited service life.

The inspection interval of steel cylinders has increased from 5 or 6 years to 10 years. Diving cylinders that are used in water must be inspected more often. When they were found to have inherent structural problems, certain steel and aluminium alloys have been withdrawn from service.

Fibre composite cylinders were originally specified for a limited life span of 15, 20 or 30 years, while steel cylinders are nowadays typically withdrawn after 70 years, or may continue to be used indefinitely providing they pass periodic inspection and testing. Since some years there exist composite cylinders that are nominated for a non-limited-life (NLL), as long as no damage is to be seen.

Types

Since fibre-composite materials have been used to reinforce cylinders, there are various types of construction of high-pressure vessels:

1. Metal only. Mostly seamless forged metal, but for lower working pressure, e.g., liquefied butane, welded steel vessels are also used.
2. Metal vessel, hoop wrapped with a fibre composite only around the cylindrical part of the "cylinder". (Geometrically there is a need for twice the tensile strength on the cylindrical region in comparison to the spherical caps of the cylinder.)
3. Thin metal liner (that keeps the vessel gas tight, but does not contribute to the strength) fully wrapped with fibre composite material.
4. Metal-free liner of plastic, fully wrapped with fibre composite material. The neck of the cylinder which includes the thread for the valve is a metal insert.

Pressure vessels for gas storage may also be classified by volume. In South Africa, a gas storage cylinder implies a refillable transportable container with a water capacity volume of up to 150 litres. Refillable transportable cylindrical containers from 150 to 3,000 litres water capacity are referred to as tubes.

Manufacturing process

Seamless gas cylinders

See also: Cold extrusion and Seamless pipe

The pressure vessel is a seamless cylinder normally made of cold-extruded aluminum or forged steel. Filament wound composite cylinders are used in fire fighting breathing apparatus and oxygen first aid equipment because of their low weight, but are rarely used for diving, due to their high positive buoyancy. They are occasionally used when portability for accessing the dive site is critical, such as in cave diving. Composite cylinders certified to ISO-11119-2 or ISO-11119-3 may only be used for underwater applications if they are manufactured in accordance with the requirements for underwater use and are marked "UW". The pressure vessel comprises a cylindrical section of even wall thickness, with a thicker base at one end, and domed shoulder with a central neck to attach a cylinder valve or manifold at the other end.

Occasionally other materials may be used. Inconel has been used for non-magnetic and highly corrosion resistant oxygen compatible spherical high-pressure gas containers for the US Navy's Mk-15 and Mk-16 mixed gas rebreathers, and a few other military rebreathers.

Aluminium

Most aluminum cylinders are flat bottomed, allowing them to stand upright on a level surface, but some were manufactured with domed bottoms.

Aluminum cylinders are usually manufactured by cold extrusion of aluminum billets in a process which first presses the walls and base, then trims the top edge of the cylinder walls, followed by press forming the shoulder and neck. The final structural process is machining the neck outer surface, boring and cutting the neck threads and O-ring groove. The cylinder is then heat-treated, tested and stamped with the required permanent markings.

• 
  Section of die with billet inserted
• 
  Cold extrusion process
• 
  Extrusion product before trimming
• 
  Section after closure of the top end
• 
  Section showing machined areas of the neck in detail
• 
  Hydrostatic test

Steel

Animation showing two stages of deep drawing of a steel plate to a cup, and a similar cup to a diving cylinder blank with domed bottom

Steel cylinders are often used because they are harder and more resistant to external surface impact and abrasion damage, and can tolerate higher temperatures without affecting material properties. They also may have a lower mass than aluminium cylinders with the same gas capacity, due to considerably higher specific strength. Steel cylinders are more susceptible than aluminium to external corrosion, particularly in seawater, and may be galvanized or coated with corrosion barrier paints to resist corrosion damage. It is not difficult to monitor external corrosion, and repair the paint when damaged, and steel cylinders which are well maintained have a long service life, often longer than aluminium cylinders, as they are not susceptible to fatigue damage when filled within their safe working pressure limits.

Steel cylinders are manufactured with domed (convex) and dished (concave) bottoms. The dished profile allows them to stand upright on a horizontal surface, and is the standard shape for industrial cylinders. The cylinders used for emergency gas supply on diving bells are often this shape, and commonly have a water capacity of about 50 litres ("J"). Domed bottoms give a larger volume for the same cylinder mass, and are the standard for scuba cylinders up to 18 litres water capacity, though some concave bottomed cylinders have been marketed for scuba. Domed end industrial cylinders may be fitted with a press-fitted foot ring to allow upright standing.

Steel alloys used for gas cylinder manufacture are authorised by the manufacturing standard. For example, the US standard DOT 3AA requires the use of open-hearth, basic oxygen, or electric steel of uniform quality. Approved alloys include 4130X, NE-8630, 9115, 9125, Carbon-boron and Intermediate manganese, with specified constituents, including manganese and carbon, and molybdenum, chromium, boron, nickel or zirconium.

Steel cylinders may be manufactured from steel plate discs, which are cold drawn to a cylindrical cup form, in two or three stages, and generally have a domed base if intended for the scuba market, so they cannot stand up by themselves. After forming the base and side walls, the top of the cylinder is trimmed to length, heated and hot spun to form the shoulder and close the neck. This process thickens the material of the shoulder. The cylinder is heat-treated by quenching and tempering to provide the best strength and toughness. The cylinders are machined to provide the neck thread and o-ring seat (if applicable), then chemically cleaned or shot-blasted inside and out to remove mill-scale. After inspection and hydrostatic testing they are stamped with the required permanent markings, followed by external coating with a corrosion barrier paint or hot dip galvanising and final inspection.

A related method is to start with seamless steel tube of a suitable diameter and wall thickness, manufactured by a process such as the Mannesmann process, and to close both ends by the hot spinning process. This method is particularly suited to high pressure gas storage tubes, which usually have a threaded neck opening at both ends, so that both ends are processed alike.

An alternative production method is backward extrusion of a heated steel billet, similar to the cold extrusion process for aluminium cylinders, followed by hot drawing and bottom forming to reduce wall thickness, and trimming of the top edge in preparation for shoulder and neck formation by hot spinning. The other processes are much the same for all production methods.

Cylinder neck

The neck of the cylinder is the part of the end which is shaped as a narrow concentric cylinder, and internally threaded to fit a cylinder valve. There are several standards for neck threads.

Welded gas cylinders

See also: Fusion welding and Rolling

A welded gas cylinder comprises to or more shell components joined by welding. The most commonly used material is steel, but stainless steel, aluminium and other alloys can be used when they are better suited to the application. Steel is strong, resistant to physical damage, easy to weld, relatively low cost, and usually adequate for corrosion resistance, and provides an economical product.

The components of the shell are usually domed ends, and often a rolled cylindrical centre section. The ends are usually domed by cold pressing from a circular blank, and may be drawn in two or more stages to get the final shape, which is generally semi-elliptical in section. The end blank is typically punched from sheet, drawn to the required sectiom, edges trimmed to size and necked for overlap where appropriate, and hole(s) for the neck and other fittings punched.

Smaller cylinders are typically assembled from a top and bottom dome, with an equatorial weld seam. Larger cylinders with a longer cylindrical body comprise dished ends circumferentially welded to a rolled central cylindrical section with a single longitudinal welded seam. Welding is typically automated gas metal arc welding.

Typical accessories which are welded to the outside of the cylinder include a foot ring, a valve guard with lifting handles, and a neck boss threaded for the valve. Occasionally other through-shell and external fittings are also welded on.

After welding, the assembly may be heat treated for stress-relief and to improve mechanical characteristics, cleaned by shotblasting, and coated with a protective and decorative coating. Testing and inspection for quality control will take place at various points.

Regulations and testing

The transportation of high-pressure cylinders is regulated by many governments throughout the world. Various levels of testing are generally required by the governing authority for the country in which it is to be transported. In the United States, this authority is the United States Department of Transportation (DOT). Similarly in the UK, the European transport regulations (ADR) are implemented by the Department for Transport (DfT). For Canada, this authority is Transport Canada (TC). Cylinders may have additional requirements placed on design and or performance from independent testing agencies such as Underwriters Laboratories (UL). Each manufacturer of high-pressure cylinders is required to have an independent quality agent that will inspect the product for quality and safety.

Within the UK the "competent authority" — the Department for Transport (DfT) — implements the regulations and appointment of authorised cylinder testers is conducted by United Kingdom Accreditation Service (UKAS), who make recommendations to the Vehicle Certification Agency (VCA) for approval of individual bodies.

There are a variety of tests that may be performed on various cylinders. Some of the most common types of tests are hydrostatic test, burst test, ultimate tensile strength, Charpy impact test and pressure cycling.

During the manufacturing process, vital information is usually stamped or permanently marked on the cylinder. This information usually includes the type of cylinder, the working or service pressure, the serial number, date of manufacture, the manufacture's registered code and sometimes the test pressure. Other information may also be stamped, depending on the regulation requirements.

High-pressure cylinders that are used multiple times — as most are — can be hydrostatically or ultrasonically tested and visually examined every few years. In the United States, hydrostatic/ultrasonic testing is required either every five years or every ten years, depending on cylinder and its service.

Valve connections

A gas regulator attached to a nitrogen cylinder. From right — cylinder valve, cylinder pressure gauge, pressure control valve (yellow) on regulator (green), outlet pressure gauge, 3-way outlet terminated by needle valves.

Valve

Gas cylinders usually have a stop angle valve at one end, and the cylinder is usually oriented so the valve is on top. During storage, transportation, and handling when the gas is not in use, a cap may be screwed over the protruding valve to protect it from damage or breaking off in case the cylinder were to fall over. Instead of a cap, cylinders sometimes have a protective collar or neck ring around the valve assembly.

Connection

The valves on industrial, medical and diving cylinders usually have threads or connection geometries of different handedness, sizes and types that depend on the category of gas, making it more difficult to mistakenly misuse a gas. For example, a hydrogen cylinder valve outlet does not fit an oxygen regulator and supply line, which could result in catastrophe. Some fittings use a right-hand thread, while others use a left-hand thread; left-hand thread fittings are usually identifiable by notches or grooves cut into them.

In the United States, valve connections are sometimes referred to as CGA connections, since the Compressed Gas Association (CGA) publishes guidelines on what connections to use for what gasses. For example, an argon cylinder has a "CGA 580" connection on the valve. High purity gases sometimes use CGA-DISS ("Diameter Index Safety System") connections.

Common cylinder valve connections

Gas type	CGA valve outlet (USA)
Acetylene	510
Air, breathing	346, 347
Air, industrial	590
Argon	580, 718, 680 (3,500 psi), 677 (6,000 psi)
Butane	510
Carbon dioxide	320, 716
Carbon monoxide	350, 724
Chlorine	660, 728
Helium	580, 718, 680 (3,500 psi)
Hydrogen	350, 724, 695 (3,500 psi)
Methane	350
Neon	580, 718
Nitrogen	580, 718, 680 (3,500 psi), 677 (6,000 psi)
Nitrous oxide	326, 712
Oxygen	540, 714
Oxygen mixtures (>23.5%)	296
Propane	510
Xenon	580, 718

Medical gases may use the pin index safety system to prevent incorrect connection of gases to services.

In the European Union, DIN connections are more common than in the United States.

In the UK, the British Standards Institution sets the standards. Included among the standards is the use left-hand threaded valves for flammable gas cylinders (most commonly brass, BS4, valves for non-corrosive cylinder contents or stainless steel, BS15, valves for corrosive contents). Non flammable gas cylinders are fitted with right-hand threaded valves (most commonly brass, BS3, valves for non-corrosive components or stainless steel, BS14, valves for corrosive components).

Common cylinder valve connections

Gas type	BS valve outlet (UK)
Acetylene	2, 4
Air, breathing	3
Air, industrial	3
Argon	3
Butane	4
Carbon dioxide	8
Carbon monoxide	4
Chlorine	6
Helium	3
Hydrogen	4
Methane	4
Neon	3
Nitrogen	3
Nitrous oxide	13
Oxygen	3
Oxygen mixtures (>23.5%)	Other guides apply
Propane	4
Xenon	3

Regulator

When the gas in the cylinder is to be used at low pressure, the cap is taken off and a pressure-regulating assembly is attached to the stop valve. This attachment typically has a pressure regulator with upstream (inlet) and downstream (outlet) pressure gauges and a further downstream needle valve and outlet connection. For gases that remain gaseous under ambient storage conditions, the upstream pressure gauge can be used to estimate how much gas is left in the cylinder according to pressure. For gases that are liquid under storage, e.g., propane, the outlet pressure is dependent on the vapor pressure of the gas, and does not fall until the cylinder is nearly exhausted, although it will vary according to the temperature of the cylinder contents. The regulator is adjusted to control the downstream pressure, which will limit the maximum flow of gas out of the cylinder at the pressure shown by the downstream gauge. For some purposes, such as shielding gas for arc welding, the regulator will also have a flowmeter on the downstream side.

The regulator outlet connection is attached to whatever needs the gas supply.

Safety and standards

It would be safer to have cylinders individually anchored in a cool place, rather than chained in a cluster in the sun, as seen here.

Because the contents are under pressure and are sometimes hazardous materials, handling bottled gases is regulated. Regulations may include chaining bottles to prevent falling and damaging the valve, proper ventilation to prevent injury or death in case of leaks and signage to indicate the potential hazards If a compressed gas cylinder tips over, causing the valve block to be sheared off, the rapid release of high-pressure gas may cause the cylinder to be violently accelerated, potentially causing property damage, injury, or death. To prevent this, cylinders are normally secured to a fixed object or transport cart with a strap or chain. They can also be stored in a safety cabinet.

In a fire, the pressure in a gas cylinder rises in direct proportion to its temperature. If the internal pressure exceeds the mechanical limitations of the cylinder and there are no means to safely vent the pressurized gas to the atmosphere, the vessel will fail mechanically. If the vessel contents are flammable, this event may result in a "fireball". Oxidisers such as oxygen and fluorine will produce a similar effect by accelerating combustion in the area affected. If the cylinder's contents are liquid, but become a gas at ambient conditions, this is commonly referred to as a boiling liquid expanding vapour explosion (BLEVE).

Medical gas cylinders in the UK and some other countries have a fusible plug of Wood's metal in the valve block between the valve seat and the cylinder. This plug melts at a comparatively low temperature (70 °C) and allows the contents of the cylinder to escape to the surroundings before the cylinder is significantly weakened by the heat, lessening the risk of explosion.

More common pressure relief devices are a simple burst disc installed in the base of the valve between the cylinder and the valve seat. A burst disc is a small metal gasket engineered to rupture at a pre-determined pressure. Some burst discs are backed with a low-melting-point metal, so that the valve must be exposed to excessive heat before the burst disc can rupture.

The Compressed Gas Association publishes a number of booklets and pamphlets on safe handling and use of bottled gases.

International and national standards

See also: American Standard Safety System

There is a wide range of standards relating to the manufacture, use and testing of pressurised gas cylinders and related components. Some examples are listed here.

• ISO 11439: Gas cylinders — High-pressure cylinders for the on-board storage of natural gas as a fuel for automotive vehicles
• ISO 15500-5: Road vehicles — Compressed natural gas (CNG) fuel system components — Part 5: Manual cylinder valve
• US DOT CFR Title 49, part 178, Subpart C — Specification for Cylinders
• US DOT Aluminum Tank Alloy 6351-T6 amendment for SCUBA, SCBA, Oxygen Service — Visual Eddy inspection
• AS 2896-2011:Medical gas systems—Installation and testing of non-flammable medical gas pipeline systems pipeline systems (Australian Standards).
• EN 1964-3 – Transportable gas cylinders. Specification for the design and construction of refillable transportable seamless steel gas cylinders of water capacities capacity from 0,5 litre up to 150 litre
• ISO 9809-1: Gas Cylinders–Refillable Seamless Steel Gas Cylinders–Design, Construction and Testing–Part 1: Quenched and Tempered Steel Cylinders with Tensile Strength less than 1 100 Mpa
• ISO 9809-2: Gas Cylinders–Refillable Seamless Steel Gas Cylinders–Design, Construction and Testing–Part 2: Quenched and Tempered Steel Cylinders with Tensile Strength Greater than or Equal to 1 100 Mpa
• ISO 9809-3: Gas Cylinders–Refillable Seamless Steel Gas Cylinders–Design, Construction and Testing–Part 3: Normalized Steel Cylinders
• EN ISO 11120 – Gas cylinders. Refillable seamless steel tubes of water capacity between 150 l and 3000 l. Design, construction and testing (ISO 11120:2015)
• EN 1975 – Transportable gas cylinders. Specification for the design and construction of refillable transportable seamless aluminium and aluminium alloy gas cylinders of capacity from 0,5 litre up to 150 litre
• EN 84/526/EEC – Aluminium high pressure gas cylinder design
• EN 12245 – Transportable gas cylinders Fully wrapped composite cylinders
• ISO 11119-1 Gas cylinders — Design, construction and testing of refillable composite gas cylinders and tubes — Part 1: Hoop wrapped fibre reinforced composite gas cylinders and tubes up to 450 l

Color coding

ISO Cylinder Colour Coding for Different Gases

Gas cylinders are often color-coded, but the codes are not standard across different jurisdictions, and sometimes are not regulated. Cylinder color can not safely be used for positive product identification; cylinders have labels to identify the gas they contain.

Medical gas cylinder color code Indian standard

The Indian Standard for Gas Cylinder Color Code applies to the identification of the contents of gas cylinders intended for medical use. Each cylinder shall be painted externally in the colours corresponding to its gaseous contents.

Common sizes

The below are example cylinder sizes and do not constitute an industry standard.

Cyl. size	Diameter × height, including 5.5 inches for valve and cap (inches)	Nominal tare weight, including 4.5 lb for valve and cap (lb)	Water capacity (lb)	Internal volume, 70 °F (21 °C), 1 atm		U.S. DOT specs
				(liters)	(cu. ft)
2HP	9 by 51 inches (230 mm × 1,300 mm)	187 pounds (85 kg)	95.5	43.3	1.53	3AA3500
K	9.25 by 60 inches (235 mm × 1,524 mm)	135 pounds (61 kg)	110	49.9	1.76	3AA2400
A	9 by 51 inches (230 mm × 1,300 mm)	115 pounds (52 kg)	96	43.8	1.55	3AA2015
B	8.5 by 31 inches (220 mm × 790 mm)	60 pounds (27 kg)	37.9	17.2	0.61	3AA2015
C	6 by 24 inches (150 mm × 610 mm)	27 pounds (12 kg)	15.2	6.88	0.24	3AA2015
D	4 by 18 inches (100 mm × 460 mm)	12 pounds (5.4 kg)	4.9	2.24	0.08	3AA2015
AL	8 by 53 inches (200 mm × 1,350 mm)	52 pounds (24 kg)	64.8	29.5	1.04	3AL2015
BL	7.25 by 39 inches (184 mm × 991 mm)	33 pounds (15 kg)	34.6	15.7	0.55	3AL2216
CL	6.9 by 21 inches (180 mm × 530 mm)	19 pounds (8.6 kg)	13	5.9	0.21	3AL2216
XL	14.5 by 50 inches (370 mm × 1,270 mm)	75 pounds (34 kg)	238	108	3.83	4BA240
SSB	8 by 37 inches (200 mm × 940 mm)	95 pounds (43 kg)	41.6	18.9	0.67	3A1800
10S	4 by 31 inches (100 mm × 790 mm)	21 pounds (9.5 kg)	8.3	3.8	0.13	3A1800
LB	2 by 15 inches (51 mm × 381 mm)	4 pounds (1.8 kg)	1	0.44	0.016	3E1800
XF	12 by 46 inches (300 mm × 1,170 mm)	180 pounds (82 kg)	134.3	60.9	2.15	8AL
XG	15 by 56 inches (380 mm × 1,420 mm)	149 pounds (68 kg)	278	126.3	4.46	4AA480
XM	10 by 49 inches (250 mm × 1,240 mm)	90 pounds (41 kg)	120	54.3	1.92	3A480
XP	10 by 55 inches (250 mm × 1,400 mm)	55 pounds (25 kg)	124	55.7	1.98	4BA300
QT	3 by 14 inches (76 mm × 356 mm) (includes 4.5 inches for valve)	2.5 pounds (1.1 kg) (includes 1.5 lb for valve)	2.0	0.900	0.0318	4B-240ET
LP5	12.25 by 18.25 inches (311 mm × 464 mm)	18.5 pounds (8.4 kg)	47.7	21.68	0.76	4BW240
Medical E	4 by 26 inches (100 mm × 660 mm) (excludes valve and cap)	14 pounds (6.4 kg) (excludes valve and cap)	9.9	4.5	0.16	3AA2015

(US DOT specs define material, making, and maximum pressure in psi. They are comparable to Transport Canada specs, which shows pressure in bars. A 3E-1800 in DOT nomenclature would be a TC 3EM 124 in Canada.)

Gas storage tubes

For larger volume, high pressure gas storage units, known as tubes, are available. They generally have a larger diameter and length than high pressure cylinders, and usually have a tapped neck at both ends. They may be mounted alone or in groups on trailers, permanent bases, or intermodal transport frames. Due to their length, they are mounted horizontally on mobile structures. In general usage they are often manifolded together and managed as a unit.

Gas storage banks

Hydrogen storage cylinders in a cascade filling system

Groups of similar size cylinders may be mounted together and connected to a common manifold system to provide larger storage capacity than a single standard cylinder. This is commonly called a cylinder bank or a gas storage bank. The manifold may be arranged to allow simultaneous flow from all the cylinders, or, for a cascade filling system, where gas is tapped off cylinders according to the lowest positive pressure difference between storage and destination cylinder, being a more efficient use of pressurised gas.

Gas storage quads

Helium quad for surface-supplied diving gas

A gas cylinder quad, also known as a gas cylinder pallet, is a group of high pressure cylinders mounted on a transport and storage frame. There are commonly 16 cylinders, each of about 50 litres capacity mounted upright in four rows of four, on a square base with a square plan frame with lifting points on top and may have fork-lift slots in the base. The cylinders are usually interconnected as a manifold for use as a unit, but many variations in layout and structure are possible.

See also

• Bottled gas – Gas compressed and stored in cylinders
• Composite overwrapped pressure vessel – Pressure vessel with a non-structural liner wrapped with a structural fiber composite
• Filling carousel – Device for filling liquefied petroleum gas cylinders
• Lecture bottle – Small gas cylinder typically used for specialty gasses
• Powerlet – A small, inexpensive, disposable metal gas cylinder for providing pneumatic power
• Storage tank – Container for liquids or compressed gas
• UN Recommendations on the Transport of Dangerous Goods – United Nations Model Regulations

Sources

• NOAA Diving Program (U.S.) (28 February 2001). Joiner, James T (ed.). NOAA Diving Manual, Diving for Science and Technology (4th ed.). Silver Spring, Maryland: National Oceanic and Atmospheric Administration, Office of Oceanic and Atmospheric Research, National Undersea Research Program. ISBN 978-0-941332-70-5. CD-ROM prepared and distributed by the National Technical Information Service (NTIS)in partnership with NOAA and Best Publishing Company

External links

• NASA — Safety Standards for Oxygen and Oxygen Handling