Shielding Gas Safety

Shielding Gas Safety

This article is intended to give users some basic information about the recommended safety procedures concerning the use of mig/tig welding shielding gases. It does not cover the use of other gases such as Oxygen or Acetylene as those need much more careful transporting, storage and handling procedures than shielding gases.


Cylinder identification:

Welding shielding gases are commonly one of three types, argon, argon & carbon dioxide mixes of various compositions and carbon dioxide.
Cylinders are colour coded;

• argon cylinders are green

• argon/co2 mix cylinders are green with a bright green shoulder

• carbon dioxide cylinders are black with a silver/grey shoulder.

Some carbon dioxide cylinders contain a Dip tube to extract the liquid from the cylinder. The tube runs down the centre of the cylinder and draws the liquid carbon dioxide up through the valve. These can be identified by the white stripe down the side - THEY ARE NOT SUITABLE FOR USE WITH REGULATORS.
All the three basic types of shielding gases are heavier than air and are asphyxiants so should only be used in well-ventilated areas.
Industrial gas cylinders typically have to be tested every 10 years to ensure they are in good order with some having a test period of 5 years.


Transporting and Handling:

• The transporting of gas cylinders is covered by the Carriage of Dangerous Goods and Use of Transportable Pressure Receptacles Regulations.
• A 2KG fire extinguisher is required by law to be carried whenever you are transporting any type of gas cylinder.
• Cylinders come in several sizes and fill pressures with some being filled to 300 bar (4350 psi) so therefore they need careful handling, storage and use. Some cylinders can weigh in the region of 100kg.
• Although not required for non-trade users, it is recommended to display a compressed gas warning diamond on your vehicle whenever you have a cylinder onboard to help the emergency services evaluate any potential hazard in the event of an incident. Removing it when you don't have a cylinder onboard will reduce the likelihood of being stopped by the authorities.

Basic cylinder safety advice:

• Only keep as much gas as you actually need. More cylinders = more risk
• Always wear appropriate hand and foot protection when moving or transporting cylinders.
• When transporting cylinders, always have an appropriate Material Safety Data Sheet (MSDS) available and be familiar with the properties of the particular gas you are transporting.
• Always secure cylinders while transporting and wherever possible, transport them upright and in an open vehicle.
• If transporting cylinders in an enclosed vehicle, always ensure you have adequate ventilation, i.e. an open window.
• If you suspect a cylinder has developed a leak during transport, park the vehicle in a safe place with the windows down and telephone the agent or the supplier for advice.
• If you are involved in a road accident, advise the emergency services that gas cylinders are being carried and show them any information relating to the cylinders, e.g. the Material Safety Data Sheet (MSDS)
• Remove the cylinder from the vehicle at the earliest opportunity, place in the proper storage area and secure it.
• Visually inspect the cylinder for damage to the body and the valve assembly, if there is any sign of damage, do not use it and inform your supplier immediately.
• Before using any gas cylinder, check that the seal is intact, also check for the proper labelling to ensure that the gas the correct one you asked for before you remove the seal.

Cylinder Use:

• Store cylinders in a well-protected, dry and well-ventilated area ensuring they do not block entry or exit routes and are protected from physical damage from striking or falling objects and from any potential tampering.
• Cylinders should also be stored out of direct sunlight.
• Use cylinders in the order in which they were received, i.e. first in - first out.
• Ensure the valve seat and regulator thread/seat are free from any foreign matter including dirt, oil or grease. Remove any foreign matter by wiping with a clean, dry cloth, by using compressed air or by briefly opening and closing the valve (known as "snifting" or "cracking"). When using compressed air or 'snifting', wear eye and ear protection and always ensure that you point the cylinder valve or air blowgun away from yourself and others.
• Fit the regulator then open the cylinder valve slowly at arm’s length. Check for leaks using soapy water.
• Always store cylinders in an upright position and secure with a chain or strap above the centre of the body.
• If a cylinder key is required to open a cylinder, always leave it in place to make it easier to close the valve after use or in an emergency. Always use the correct key, they cost no more than a few pounds at most.
• Always close the cylinder valve after use.
• Always close the valve when the cylinder is empty to prevent air or moisture from entering the cylinder.

Things Not To Do:

• Do not attempt to lift a large cylinder single-handed.
• Do not roll a cylinder horizontally to move it.
• Do not carry a cylinder by the valve.
• Do not leave an open cylinder unattended.
• Do not leave a cylinder unsecured.
• Do not leave cylinders in hot cars.
• Do not force incorrect fittings onto the wrong cylinder.
• Do not use grease, oil or ptfe tape on the regulator or valve thread/seat.
• Do not attempt to refill a cylinder or decant gas from one cylinder to another. This is especially important with pub type CO2 cylinders, they can suffer from severe internal corrosion due to any beer or soft drinks in the gas line being forced into the old cylinder when a new cylinder is connected. See this scary HSE document for more details!
• Do not attempt to mix gases in a cylinder.
• Do not fill a cylinder with a gas different to the one it originally contained.
• Do not remove or deface cylinder content identification labels.
• Do not tamper with cylinders in any way.
• Do not attempt to repair a cylinder.
• Do not repaint cylinders in a different colour to the original.
• Do not disguise any damage to cylinders.
• Do not discard cylinders, return them to the correct agent or supplier.
• Do not use a co2 regulator on an argon or argon mix cylinder unless the regulator is specifically designed to handle the higher pressure.

Disposal of used cylinders:

When you enter into a rental agreement, you are only purchasing the contents of the cylinder, not the cylinder itself which always remains the property of the supplier (not the agent). Empty cylinders should be returned to their respective suppliers.

If the agent will not accept a returned cylinder, maybe due to age, missing labels, unknown contents, damage, etc., contact the supplier for assistance. If the supplier cannot help then it should be taken to a recycling centre for proper disposal.


Useful links:

Boc Industrial; gas safety, cylinder safety, material safety data sheets (MSDS) (PDF)
Health and Safety Executive (HSE);
Safe use of compressed gases in welding, flame cutting and allied processes. (PDF)
British Cylinder Gas Association (BCGA); Carriage of gas cylinders by road in cars, vans and other vehicles (PDF)