Flammable gases
Flammable gases in the right concentration in air or oxygen burn or explode when ignited. If the mixture is too lean or too rich it will not ignite. Rich mixtures, however, are dangerous because they may form explosive mixtures at the outer edge of an area.

Acetylene, ammonia, hydrogen, propane, propylene and methane are all flammable gases, also known as fuel gases. They burn when mixed with an oxidant and provided with a source of ignition. Starting from low concentrations,the risk of fire increases as the percentage of fuel gas rises. Once the concentration exceeds the higher value (UEL), the air becomes “too rich” to burn, reducing the chances of ignition.

In any container or confined space, even small quantities of escaping fuel gas can form an ignitable mixture under the right conditions. Yet there is also a small risk of fuel gases reaching their lower threshold limit in open spaces or large, naturally ventilated work areas. Fuel gas that has leaked may form an ignitable mixture with the surrounding air, resulting in fire or explosion. Some of these gases are therefore odorised so that leaks can be more easily identified by smell.

Toxic & corrosive gases
Compressed gas or vapor that has a median lethal concentration (LC50) in air of 200 parts per million (ppm) by volume, or 2 milligrams per liter or less of mist, fume, or dust, when administered by continuous inhalation for one hour (or less if death occurs within one hour) to albino rats weighing between 200 and 300 grams each.

Oxidisers
Oxidisers are not flammable, but they contribute to combustion of other materials by yielding oxygen. Oxidisers in concentrated and/or pressurized state should not come into contact with even the smallest amounts of grease, oil or any organic material. Air, nitrogen dioxide and oxygen are common oxidisers. If for example oxygen is not handled correctly, the surrounding atmosphere can become enriched with oxygen. The information here details the dangers of enrichment and the simple measures required to use oxygen safely.

Atmospheric gases are non-toxic. If their concentrations change, however, they can have an impact on life and combustion processes (especially in the case of oxygen). A sufficient amount of oxygen must be present in breathable atmospheres. Oxygen itself is not flammable, but it does support combustion.

• Fire hazards from oxygen enrichment
  Oxygen reacts with most elements. The initiation, speed, vigour and extent of these reactions depend on a number of factors including the concentration, temperature, pressure of reactants, ignition energy and the mode of ignition.
• Combustibility of materials
  The risk of fire increases considerably when the concentration of oxygen in an atmosphere rises, even if it is just by a few percent. Sparks that under normal conditions would be harmless can cause fires in oxygen enriched atmospheres, and materials that would not normally burn in air - including fireproof materials - may burn vigorously or even spontaneously.
• Hydrocarbon oil and grease
  Oil and grease are particularly hazardous in the presence of pure oxygen as they can ignite spontaneously and burn with explosive violence. They should never be used to lubricate oxygen or enriched-air equipment (special lubricants which are compatible with oxygen can be used under certain conditions).
• Smoking
  Many combustion accidents are triggered when cigarettes are lit in oxygen-enriched atmospheres. The risks of smoking in oxygen-enriched atmospheres or places where oxygen enrichment may occur are extremely high. Smoking must be forbidden in all such areas.

Inert gases
Inert gases reduce oxygen levels and limit combustion when fed into a room or confined space. They are used in extinguishing systems in areas where water would cause too much damage, for example in rooms with electronic devices.

Nitrogen and argon inhibit combustion. Any changes in the concentration of these gases cannot be detected by human senses. If they are not handled correctly, accidents may occur.

In order to be stored as liquids, these gases have to be cooled at extremely low temperatures (less than -180 ºC at atmospheric pressure). In this state, they can rapidly cause cold burns and make certain materials brittle, which in turn may lead to structural failure.

Hazards from oxygen deficiency
Oxygen is essential to life. Although a healthy person may survive short exposure to oxygen content as low as around 16%, an adequate oxygen supply must be present in any atmosphere being breathed by humans. A drop in oxygen levels is not accompanied by any immediate signs, making deficiency impossible to detect by human senses.

Causes and prevention of oxygen deficiency
Oxygen deficiency can be prevented by observing the following measures:

• Leaks of gases other than oxygen automatically lead to oxygen deficiency. New equipment which uses inert or any other gas should be thoroughly checked for leaks using a timed gas pressure drop test plus a leak test with an approved leak detection fluid that is compatible with the equipment in question.
• All equipment, including pipes and hose connections, should be properly fitted. Hoses and other equipment should be kept leak-tight and protected against damage. All maintenance and repair work should be carried out by experienced and fully qualified personnel.
• When the work period is over, the cylinder valve or piped supply stop valve must be turned off in order to avoid leakage between two working periods. The valves on welding equipment should not be relied upon as shut-off valves for the gas supply. Gas cylinders in use should not be handled roughly, knocked or pulled over.
• A small amount of liquefied gas can vaporise into a large amount of gas. Liquid spills can therefore rapidly cause oxygen deficiency in confined spaces. Tanks and equipment for storing and handling liquid gases should be inspected carefully and maintained in accordance with relevant regulations and recommendations.
• Vented gases often have low oxygen content. Work should not be carried out in these atmospheres.
• Oxygen deficiency arises when plant items such as vessels are purged with nitrogen or other inert gases in preparation for repairs.
• Processes that involve the vaporisation of liquid nitrogen, such as food cooling, ground freezing, cryogenic surgery and blood plasma preservation, automatically lead to oxygen-deficient atmospheres. People should not enter these areas without adequate breathing equipment, even if the atmosphere is only slightly deficient in oxygen. Those kind of areas should be equipped with appropriate detectors and alarm systems.
• All gas welding and heating processes extract oxygen from air. These processes can lead to oxygen deficiency if the workspace is too small and poorly ventilated.
• Removing argon, carbon dioxide or any other cold gas from large vessels and deep pits can be difficult as these gases are denser than air. Air fed in to the bottom of these spaces tends to float up through the dense gas without displacing it. This means that purging can take much longer than expected.

Detecting oxygen enrichment or deficiency
Areas where the oxygen content can change to a dangerous extent must be continuously monitored using instruments that show increases and decreases in the concentration of oxygen in the ambient atmosphere. In confined spaces, these instruments should be located as close to workers as possible. Ideally, workers should have a portable instrument attached to their work clothes.

Discontinuous measuring methods should only be used if the tendency for dangerous changes in oxygen content can be detected quickly in the time between any two measurements. Oxygen content is not the only factor that defines whether a space is safe or not. Atmospheres can be affected by other gases such as fuel gases and nitrogen oxides used with cutting or heating torches. These should be monitored wherever necessary.

Preventive measures

• Apparatus used for the manufacture, distribution and utilisation of inert gases must be installed and identified in accordance with the recommendations of the industrial gas industry, and must comply with relevant regulations.
• Any leaks must be dealt with by persons with adequate training and proper equipment.
• Workers and first aiders should know what to do in the event of an incident.
• Operating personnel must at all times obey site rules and regulations and wear protective equipment where necessary.
• All persons working in spaces at risk from oxygen deficiency or enrichment should be adequately informed of the risks involved. Special attention should be drawn to the insidious nature of the risks and how rapidly they can develop without any indication to workers.

Linde offers trainings about risks involved in gas application as well as mitigating measures to take.

Cylinder safety

Making it safe for our customers to handle and use our gases

Our cylinders are colour-coded in line with the European standard EN 1089-3, making them easy to identify from long distances. You can find a summary of the characteristics of the most common industrial cylinders below. Each gas cylinder should be accompanied by the corresponding Linde material safety data sheet (MSDS).

You can identify the gas inside a cylinder based on the cylinder’s label or collar. The label also provides vital safety information. These are the different elements of a typical cylinder label:

• Product name
• Physical properties
• Warning symbols
• Gas code
• Transportation information
• Safety information

Linde gas cylinders are designed and manufactured in line with international standards and specifications. These guidelines define the material from which the cylinders are made, the method of manufacturing, the test pressure, maximum permissible filling pressure and the regular testing method.

Maintaining and testing cylinders
If you own your cylinders, you must be aware of and comply with statutory obligations regarding maintenance and regular testing. If you rent your cylinders from Linde then Linde – as the owner of those cylinders – ensures that these regulations are met.

Cylinder valves and security caps
All Linde cylinders that contain gas at high pressure are fitted with a cylinder valve. This must not be removed or tampered with at any time except to tighten the gland nut when necessary. All filled cylinder filled with gas should be kept with a valve cap at all times when not in use! Some cylinders have a shrink-foil, a plastic cap or a tape over the cylinder valve indicating that they have been filled and checked. Each valve outlet is specially threaded to fit standard pressure regulators available at Linde sales points.

Regardless of whether gas cylinders contain flammable or non-flammable gases, all cylinder valves are opened by turning the spindle anti-clockwise and closed by turning the spindle clockwise.

Important

• NEVER open an acetylene cylinder valve completely. A half turn is sufficient.
• NEVER leave the opened spindle of any cylinder valve against the backstop.
• NEVER tamper with cylinders in any way. If in doubt ask your gas supplier.
• NEVER attempt to repair a cylinder.
• NEVER hide damage to cylinders.
• NEVER mix gases in a cylinder.
• NEVER transfer gas to another cylinder.
• NEVER scrap a cylinder you do not own.
• NEVER use adaptors to connect regulators or hoses that are not approved for that gas.
• NEVER expose cylinders to elevated temperatures (> 55°C)

Pressure relief devices
Certain cylinders are fitted with pressure relief devices. These can be either relief valves (which re-seal when pressure falls to normal) or bursting discs (which discharge content completely). This disc is fitted on the cylinder valve.

Identifying Cylinders
The cylinder label is the primary means of identifying the properties of a gas in a cylinder. The cylinder’s colour coding, however, provides a further guide to content.

Gas cylinders storage

Finding the right place to store your cylinders safely

Gas cylinders are large, heavy and relatively unstable due to the small base-diameter to height ratio. For your safety, it is important to adhere to a few simple rules when storing your gas cylinders:

• Store cylinders appropriately.
• Store cylinders in a well-ventilated covered area, preferably outside on a level, well-drained surface in the shade.
• Store cylinders vertically and secured to prevent them from falling over.
• Store full and empty cylinders separately, rotating your cylinder stock so that the oldest cylinders are used first.
• Separate cylinders according to gas properties (flammable, inert, oxidant and so on). Cylinders with flammable content must be stored separately from other cylinders.
• Safety signs must be displayed in storage areas in line applicable legal requirements.

Be aware of the properties of the individual gases, the specific requirements for certain products. Cryogenic, liquefied and compressed gases that are heavier than air can collect in low-lying areas such as drains, basements and ducts. Take these aspects into consideration when storing these gases. Pay attention to th electric components in the storage area. If you are storing flammable gases, electric equipment must meet certain specifications.

Remember:

• Never store flammable cylinders with other gas cylinders.
• Never store other products with cylinders, particularly flammable materials such as fuel, oil, paint or corrosive liquids as this may result in a hazardous situation.
• Never store LPG cylinders within five meters of other gas cylinders. This distance can be reduced if the cylinders are separated by a firewall.

Transporting cylinders

Getting your gases to the point of use in complete safety

When you collect cylinders from a Linde sales point, the Linde agent will inform you of your obligations regarding the carriage of dangerous goods. Anyone transporting gas cylinders in a vehicle should follow basic safety requirements:

• Drivers should be trained in the hazards and dangers of the goods they are handling, the safe handling of gas cylinders and emergency procedures and the use of fire-fighting equipment
• All training should be recorded and the records should be kept by both the employee and employer.
• Employees should regularly participate in refresher courses that cover any changes to regulations. Employers should verify which courses new employees have attended.
• Gas cylinders should be transported in open vehicles. If this is not possible, vehicles should be well ventilated. Toxic gases must not be carried in a closed vehicle unless it has been specifically designed for this purpose.
• The transport of toxic materials require some additional measures and equipment and should never been carried out by untrained personnel!
• All vehicles carrying gas cylinders must be equipped with a two kg fire extinguisher for fighting engine and cab fires.
• Cylinder valves must be closed whilst in transit and any equipment disconnected. Furthermore the cylinder cap must be attached for transport.
• Cylinders should be secured properly and should not project over the sides or ends of the vehicle.
• All Linde cylinders have cylinder labels produced in accordance with applicable legislation. These labels must never be removed or defaced.
• In the event of a suspected leak, park the vehicle in a safe place and contact Linde. If it is a serious incident, contact the emergency services.
• If your load exceeds a certain threshold, you may need to take additional safety precautions. It is every driver’s responsibility to know whether the load they are carrying is above this threshold.
• Cylinders must be transported on company or private grounds with the same amount of care as on public roads. They must be properly secured when being moved and, if transported in a van, precautions must be taken to avoid gas building up and affecting the driver.

Handling cryogenic gases

Taking the precautions necessary to ensure that cryogenic gases do not pose a safety risk

A cryogenic liquid is a liquid cooled below its normal boiling point below –130°F (–90°C). Argon, helium, hydrogen, nitrogen and oxygen are the most common industrial gases transported, handled and stored in a liquid state at cryogenic temperatures.

Due to these extremely low temperatures and the high rate at which these gases can convert from liquid to gas, a number of precautions and safe practices must be observed. Specific precautions must also be followed to prevent liquid reacting with contaminants or other hazards associated with particular products such as asphyxiation or flammability.

Visit our safety documents section to find out which safety guidelines must be applied by you. As always, end users should be thoroughly familiar with the product-specific Material Safety Data Sheet (MSDS). All operators must have a thorough knowledge of the equipment required in conjunction with cryogenic gases.

Danger of suffocation
How do you prevent the risk of suffocation when working with cryogenic gases such as nitrogen, carbon dioxide or argon? That's what this video explains. If, after watching the film, you have any questions about the possibility of a safety check by a Linde specialist in your company or institution, please contact us via our online contact form.

Safe use of dry ice

The necessary precautions for working with dry ice

Cryogenic gases are extremely cold; also dry ice (carbon dioxide in solid form), with a product temperature as low as -78.9 ºC. The released carbon dioxide gas displaces the oxygen present in an enclosed space. Room monitoring limits the risks here. When using dry ice, there are a number of general precautions to limit the risks for skin, eyes and breathing. In case of an accident with dry ice, always contact the nearest doctor immediately.

Important

• Dry ice has a temperature of -78.9 ºC. Contact with, for instance, the skin can lead to blisters or even burns.
• When overfilling dry ice from a large container into a small one, dry ice can fall out. Therefore, do this slowly and carefully!
• When working with dry ice, wear a face shield or safety goggles with eye caps.
• Wear the specially insulated gloves for handling dry ice. Normal work gloves are insufficient.
• Keep dry ice separate from the driver during transport. Never in the cabin or in the passenger compartment of the car.
• If you store dry ice, ventilate well. The carbon dioxide that is released and that spreads just above the floor is suffocating. It displaces the oxygen. It is advisable to install a gas detection system.
• Dry ice should never be used as ice cream and should not be touched with bare hands. Keep dry ice out of reach of children.
• Dry ice may only be stored in suitable containers.

Safe use of equipment

Preventing accidents by handling equipment in a safe way

If not properly maintained by professionals, Leaks can develop in any part of a gas supply system. Joints are particularly vulnerable. So it is crucial that you monitor all links in your supply system. The right gas equipment and manifolds can help you store gas correctly, regulate flow rate and pressure and prevent major accidents resulting from leaks. We offer a comprehensive range of safety-certified gas equipment such as manifolds, regulators and valves. We also offer advice to help you observe the correct safety practices.

All equipment in a gas supply system must be checked for leaks after assembly/installation. Any necessary adjustments must be made before the supply is turned on. Always use leak detection liquid when testing equipment. Linde also offers professional gas detection devices. Do not use soapy water or washing up liquid. Our leak detection spray TL-4 is perfect for industrial systems. Make sure that the leak detection solution is compatible with the equipment materials. ALL joints should be tested.

• Apply the leak detection liquid to joints and any potential leakage points, such as the connection point between the cylinder valve and the regulator
• Never apply leak test liquids to a cylinder valve outlet
• If any frothing occurs, depressurise the system immediately and correct the leak
• Do not use the equipment until the leak has been rectified
• Ensure the area is dry by wiping it with a clean, lint-free cloth after the check
• Once the leak has been rectified, re-purge air from the system before use.

Regularly check for faults and leaks
Hoses with leaks, cuts, burns or localised surface damage should be replaced with new industry-approved fitted hoses. Regularly examine the cutting or welding nozzle. If it is becoming clogged, clean or replace it. Keep equipment clean. Oxygen regulators in particular must be kept in a clean area when not in use. If a pressure regulator is defective, replace it immediately.

Leaks around the cylinder valve spindle
If there is a leak around the spindle of the cylinder valve, you will hear a hissing sound and, in the case of fuel gases, smell the escaping gas. Do not use the cylinder and do not attempt to repair the leak. Move the cylinder to an area where the leak can disperse safely, label it and advise us. If your manometer is broken, you can purchase a new one as a spare part from Linde. Never remove, change or tamper with the pressure gauges on a pressure regulator. If a gauge leaks, take the whole pressure regulator to Linde and ask for advice.

Connecting your gas cylinders safely to a manifold
Whether you wish to use individual gas cylinders or connect your cylinders to a manifold, we have the supply solution to suit you. We provide cylinder-bundles for customers who require larger quantities of gas and have adequate handling facilities to offload them from the delivery vehicle and transport them to and from the point of use. Customers should never remove individual cylinders from cylinder-bundles - they are designed and supplied as units. The unauthorised removal of individual cylinders may result in a dangerous situation. Manifolds should be planned and installed by experts working in compliance with relevant regulations.

Advice on gas equipment
To ensure the personal safety of anyone handling our gases, we advise our customers on protective gear and equipment such as hoses and flashback arrestors.

Hoses
Hoses for welding cylinders should be of the highest quality and meet European standards. Linde’s offers a range of top quality hoses. Inferior hoses harden and may crack, leak or ignite internally if oxygen gets into the system. Never use water hoses for gas supply systems. Hoses should be the correct length and not longer than necessary. However, they must be long enough to allow cylinders to be positioned safely, away from sparks and hot metal. Do not coil surplus hose around the cylinder or regulator or on the floor close to cylinders. A fire in a coiled hose is very difficult to extinguish. Surplus hose should be positioned behind the welder to keep it clear of sparks. Hoses should not be positioned underneath the cutting/welding area.

Bad hose connections are a frequent cause of accidents. Fitted hoses from Linde are supplied with the ends firmly attached to nipples together with loose nuts for connections to regulator outlets and blowpipe inlets. We also supply traditional hoses with hose clamps. Never use old or used clips for hose connections. Twisted wire can cause serious injury if the hose works loose and flails about. Check connections regularly and remember to purge hoses before lighting a cutting or welding torch.

Hose check valve and flashback arrestors
Flashbacks can and do occur if oxyfuel gas equipment is not operated at the correct pressures, if the correct procedures are not observed or if nozzles become blocked. Faulty or leaking equipment can also cause flashbacks. Back feeding is another main cause of flashbacks and occurs when higher pressure gas feeds back up a lower pressure stream.

A hose check valve prevents oxygen and fuel gas mixing in the hose and subsequently causing fire, injury and damage. A flashback arrestor is designed to quench the flashback and, in conjunction with a cut-off valve, automatically shut off the gas flow. These multifunction devices provide an additional safeguard, particularly in locations such as hospitals, garages, and workplaces with flammable or hazardous chemicals, where fire resulting from a flashback would be especially dangerous. Any equipment that uses oxygen must be specifically approved for this use. Flashback arrestors should be fitted to all fuel gas supply lines and oxygen supply lines used in conjunction with fuel gases. Regulations regarding oxygen and flashback arrestors differ from country to country. We recommend using flashback arrestors with four safety features including a pressure sensitive shut-off valve that has to be opened manually before the gas can flow.

The correct clothing and protective equipment
When welding or cutting, operators must wear goggles with double lenses (carrying the CE mark). The inner lens should be tinted and the outer lens clear. The clear outer lenses should be changed regularly when spatter builds up. Eye protection (spectacles or goggles carrying the CE mark) should also be worn when handling high pressure gases in order to protect eyes against dust particles or the impact of a gas stream.

Do not wear clothes made of highly flammable materials. Leather gloves or gauntlets should be used where necessary. Additional protective clothing may be required in certain work environments.