Safety risks from welding

Confined space working

The main risk from confined space working is the lack of oxygen. You may be working in an identified confined space, but you should also be aware if your workspace could become a confined space as you weld.

Inert gases and some common chemical reactions (for example rusting) can reduce the amount of oxygen inside enclosed spaces such as tanks, pipes and pits. Working in these locations is dangerous.

Plan before you enter a confined space:

consider if there is a way to do the job without going in
if you have to go in, use a safe system of work. Confined spaces: A brief guide to working safely gives more guidance on this
make sure you know what the emergency rescue plan is
never use oxygen supplies to 'sweeten' the air (this is a very serious fire risk)

Welding gases such as argon, carbon dioxide, nitrogen and helium can displace the air inside enclosed spaces. Argon and carbon dioxide are relatively 'heavy' gases. They can pool in places where you do not normally expect to have a problem, for example vehicle inspection pits.

Sometimes inert gases are used to deliberately replace the air to prevent weld oxidation or reduce the risk of fires. Gases may also build up as they are used during the welding process. If you don't follow the safe system of work and enter an area where there is a large amount of inert gas, you are risking death from asphyxiation.

If the amount of inert gas is high enough, you won't cough, splutter, pant or feel breathless. You will simply pass out. It happens so fast you will not be able to rescue yourself. Asphyxiation hazards in welding and allied processes gives more guidance on this.

If the inert gas has only partially replaced the air, you may feel very weak, tired and confused. You are likely to find you cannot complete simple tasks, including finding the way out. If you aren't rescued and breathing normal air within a few minutes, you are likely to pass out and eventually die.

Most welding gases, including all the inert gases, have no smell.

There are specific methods for confined space working. Confined spaces: A brief guide to working safely has a useful list of points to consider. Dangerous substances and explosive atmospheres gives more guidance on permit-to-work systems.

Preventing fire and explosion

Clear away wood, fabric, cardboard and other flammable material before starting a welding job. Heat, sparks and drips of metal and slag can travel a considerable distance and start fires in adjacent rooms.

Where hot work cannot be carried out in a safe area, or where combustible material cannot be removed from the work area, a fire watch should be maintained during and after the hot work. This watch should be maintained for at least 30 minutes after the completion of the hot work, but where an unintended ignition may be difficult to detect or slow to develop, this may need to be extended to 60 minutes.

Welding and cutting inside ships and other enclosed spaces is particularly dangerous as smoke from fires cannot escape and will quickly overcome people working nearby.

There is more detailed information on HSE's fire and explosion web pages.

Hot work on tanks and drums which may have had flammable liquids in them

If you are going to weld or flame cut drums and tanks, empty and clean the inside of the tank or drum first to prevent the risk from fire and explosion. HSE guidance Hot work on drums and tanks gives a simple description of the safe way to do this work.

Transporting acetylene in a van

Acetylene is very explosive, even in small amounts. A leak of acetylene gas in to the back of a van can cause a serious explosion. If you carry a gas cylinder inside a vehicle, always close the main cylinder valve to prevent leaks.

The British Compressed Gases Association publish relevant guidance.

Electrical hazards

The arc welding process requires a live electrical circuit. This means all arc welders using hand-held equipment are at risk of electric shock and electrical burns. The risk for MIG/ MAG and TIG welding is much less, as the welding current is normally switched on and off using the trigger or foot switch.

For all arc welding, make sure:

welding equipment conforms to the appropriate international (ISO) or British (BS) standards
installation of fixed welding equipment is carried out by a suitably qualified person and is connected as recommended by the manufacturer
the insulation on the welding and current return leads is undamaged and the conductor is thick enough to carry the current safely
all connectors are clean, undamaged and correctly rated for the current required
insulation on the welding cables, plugs, clamps or torch/electrode holder on welding equipment is undamaged
welders use the appropriate personal protective equipment for the task

The welder is responsible for daily equipment checks and reporting defects. Employers should have a programme of regular checks for fixed and mobile welding sets. There is more guidance on maintaining electrical equipment on HSE's maintaining electrical equipment safety web page and in the HSE publication Maintaining portable and transportable electrical equipment.

Stray welding currents

For most welding operations, it is better to clamp the current return cable close to where you are welding.

Stray welding currents are electrical currents that return to the welding set by paths other than along the welding return cable. Stray currents may be substantial and comparable to the welding current, resulting in a risk of electric shock, burns and damage to property. Stray currents are more likely if the welding return path exhibits a high electrical resistance, for example the return is clamped onto a rusty surface rather than clean metal.

When welding on large structures and pipework installations, avoid clamping the welding return to handrails, pipes or the frame of the structure unless they form part of the workpiece itself.

Some older MMA welding sets are built specifically to use an earth return cable that is shared between several welding sets. These sets were common in the shipbuilding and ship repair industry and should only use equipment designed to be used this way. The current return path should be as short as possible. You may need to plan the return path carefully to minimise risk.

Three-phase electrical supplies

When using 3-phase welding circuits or single-phase circuits derived from different phases of the mains supply, segregate the welding positions connected to different phases or transformers by partitions, or distance, whenever reasonably practicable. This reduces the possibility of electric shock from simultaneous contact with any parts of 2 different systems, irrespective of the voltage of either one to earth.

Welding where there is an increased risk of electric shock

If you are in control of operations where there is a need to:

weld in damp or wet conditions
position the welder inside a metal structure, for example inside a tank
position the welder on the metal workpiece

you may need to provide an insulating mat or some other dry platform, so welders are not in direct contact with wet or conductive surfaces. Often a wooden pallet or rubber floor mat will be enough. The mat should be large enough to protect welders if they kneel or lie down to complete a task.

Welders should wear clean, dry welding gloves and overalls. Overalls or other clothing should be worn to minimise the amount of bare skin, particularly on arms and legs.

Welding PPE is not designed to prevent electric shock, but it does provide some protection. The electrical resistance of damp or contaminated clothing may be significantly reduced, giving rise to a greater risk of electric shock.

When MMA welding, it is better to use a welding set that has an open circuit voltage (no load voltage) limiting device. These devices reduce the risk of electric shock from inadvertent contact with the electrode.

HSE's electrical safety web pages have more information, in particular the page for work with electrically powered equipment.

Offshore welding

Unlike factory welders, onsite welders will face highly variable circumstances and conditions. So the health and safety measures you should take may also change frequently. Many of the risks an onsite welder will face are the same as other industrial workers (for example working at height, lifting and slinging, manual handling). HSE's offshore web pages give more guidance.

Slips and trips

The latest figures show that slips, trips and falls account for a large proportion of reported accidents. Companies who manage their slip and trip risks effectively can reduce these types of accidents. The solutions are often simple and cost effective.

The HSE leaflet Preventing slips and trips at work: A brief guide and the slips and trips web pages give simple guidance on what to consider when you are doing your risk assessment.