Welding fume is produced when metals are heated above their melting point, vaporise and condense into fumes. Exposure to various gases can also occur during welding which may include nitrogen oxides, carbon monoxide and ozone. Exposure to welding fume can cause a range of serious health effects. There is no known level of safe exposure to welding fume and employers are required to put in place suitable exposure control measures.

What is welding fume?

Welding fume is a complex and variable mixture of gases and particulates of varying sizes. It is produced when metals are heated above their melting point, vaporise and condense into fumes. The fume consists of very fine particulate which comes mostly from the consumable products i.e. the rod, wire and flux material.

The composition of welding fume can be affected by:

  • the welding process used
  • parent metal and consumable product
  • surface coatings such as primers, resins and galvanising
  • contaminants such as grease and oils
  • degreasing agents
  • rust

Exposure to various gases can also occur during welding which may include nitrogen oxides, carbon monoxide and ozone.

What are the health effects of welding fume?

In 2018 the International Agency for Research on Cancer (IARC) classified welding fume as a Group 1 carcinogen. They concluded that there is sufficient evidence in humans that welding fume causes lung cancer with limited evidence that it has the potential to cause kidney cancer. IARC also concluded that ultraviolet radiation from welding causes melanoma in the eye (a cancer that affects the eye).

Exposure to welding fume can cause a range of serious health effects. Some studies suggest that exposure to manganese, present in mild steel welding fume, can lead to neurological symptoms similar to Parkinson’s disease.

A range of respiratory illnesses may also result from exposure to welding fume and gases and include the following:

  • metal fume fever
  • chronic obstructive pulmonary disease (COPD)
  • asthma
  • an increased susceptibility to pneumonia

There is no known level of safe exposure to welding fume and employers are required to put in place suitable exposure control measures.

It should be noted that there is also a significant risk from asphyxiation when welding in confined spaces.

Assessing the risk from welding fume

Employers are required to consider the risks associated with exposure to welding fume and associated gases. Several factors are important in making an assessment and should include consideration of the following:

  • welding process, volume of work and level of fume generated
  • size of the component being welded
  • welding position i.e. flat, horizontal, vertical or overhead
  • metal being welded (mild steel, stainless steel, etc.) and consumable being used
  • where the welding is taking place i.e. indoors, outdoors or in a confined space
  • existing measures in place to control fume e.g. local exhaust ventilation (LEV), respiratory protective equipment (RPE), mechanical general ventilation.

Further information for employers on how to conduct a risk assessment is available at the following link:

How welding fume should be controlled?

The objective of the Control of Substances Hazardous to Health Regulations (Northern Ireland) 2003 (COSHH) is to prevent, or adequately control, exposures to substances hazardous to health so as to prevent ill health. The control of welding fume is only considered adequate if the principles of control in Schedule 2A of COSHH have been  applied and exposures are below any Workplace Exposure Limit (WEL) for substances within the fume e.g. manganese. There is no one control solution for welding fume and it is likely a combination of measures will be required to ensure adequate control.

An occupational hygiene air monitoring survey may be required to measure welders’ exposure to welding fume. Such a survey will assist employers in confirming the effectiveness of existing control measures such as local exhaust ventilation, and help determine whether additional respiratory protective equipment may be required.

In many instances LEV systems may not be able to achieve and maintain consistent capture of welding fume e.g. where frequent repositioning of capture hoods is required when working on large workpieces with long runs of welds. On-torch extraction can be an effective fume control option for MIG welding under certain conditions. Integration of the LEV system with the welding torch means the extraction moves with the weld and remains close to the source at all times. Where consistent and reliable fume capture cannot be maintained, RPE is required as a supplementary control measure.

Employers are required to ensure exposure is reduced to as low a level as is reasonably practicable (ALARP) where the risk assessment identifies substances that are known to cause occupational asthma.  Examples include nickel and hexavalent chromium which are contained within stainless steel welding fume. Under such circumstances fume extraction at source e.g. LEV and RPE will be required to reduce exposure to ALARP.

LEV cannot be relied on to provide effective fume capture outdoors. For welding activities conducted outside, suitable RPE must be provided. Consideration should also be given to any other person in the vicinity that may be exposed to welding fume.

As a further aid to identifying suitable control measures, employers can use the Breathe Freely Welding Fume Control Selector Tool (link below in Resources section)

Welding hierarchy of control

Employers should always consider whether it is possible to eliminate the health risks associated with welding. Alternatives to welding may include cold joining techniques using mechanical fasteners (bolts, rivets etc.) or adhesives.

Where welding cannot be eliminated consideration should be given to the following:

  • reducing the amount of welding
  • using a consumable that produces less fume
  • using a welding process that produces less fume
  • making sure the metal has been properly cleaned and prepared
  • automating or mechanising the process or job
  • using other engineering controls such as LEV

Additional consideration should also be given to management and administrative control measures. Some examples may include the provision of a dedicated area for welding thereby minimising exposure to other workers in the workplace.

The hierarchy of control places the use of personal protective equipment as the least preferable control measure in terms of overall priority. In most cases however a combination of control measures will need to be required to ensure adequate control of welding fume.

Further information relating to the measures that should be considered in order of priority can be found within BOHS guidance entitled Welding Hierarchy of Control:

More detailed guidance in relation to the control of welding fume is available within COSHH essentials sheet WL3 - Welding Fume Control.

Local exhaust ventilation (LEV)

Where it has not been possible to eliminate the need for welding, or substitute the welding technique with a less hazardous one, employers should then consider possible engineering controls. Engineering controls in the context of welding fume include suitable local exhaust ventilation (LEV) to remove the fume at source.

A range of LEV is available depending on the size of the workpiece being worked on. In every case employers should ensure that extraction systems are suitably designed for the welding process taking place.

For small workpieces, an extracted bench or booth can be used to draw fume away from the person welding. Unlike moveable capture hoods, the extraction system does not need to be repositioned during welding to maintain adequate fume capture.

LEV is also available for larger work pieces such as items that are too large to place on a work bench. On-torch extraction systems are an effective fume control option for MIG welding, assuming they are set up and used correctly. On-torch extraction is more effective when welding on flat surfaces. As welding fumes rise, it is important to ensure the extract nozzles are above the welding point meaning that on-tool extraction is not always practical e.g. when welding overhead.

LEV systems with moveable capture hoods provide a further option to employers for controlling welding fume when working on larger work pieces. It should be noted that the efficiency of swing-arm hoods is reliant upon workers correctly placing hoods to ensure the welding fume is captured.

In many cases it is likely that LEV alone will not be able to achieve and maintain consistent capture of welding fume e.g. using a moveable capture hood that requires frequent repositioning of the capture hood for larger work pieces. Under such circumstances supplementary RPE will be required to ensure worker protection.

In some cases the provision of LEV may not be reasonably practicable e.g. when welding at height or outdoors. Where LEV is not reasonably practicable, employers should ensure suitable respiratory protective equipment (RPE) is provided to relevant employees.

Other reasonably practicable control measures should also be considered and may include segregation of the area where welding is taking place and general ventilation.

Respiratory Protective Equipment (RPE)

Where fume extraction alone cannot provide adequate control, supplementary RPE should be worn to protect the health of the person welding. Welding practices that produce higher levels of fume will require a combination of LEV and RPE to be used. Examples of welding processes which generate high levels of fume include manual metal arc (MMA), flux cored arc (FCA) and metal inert gas (MIG).

The following guidelines should be followed when using RPE to control welding fume:

  • RPE provided to employees should have an assigned protection factor (APF) of at least 20.
  • For work not expected to exceed one hour, a FFP3 tight-fitting disposable mask or reusable half-mask with a P3 filter may be adequate to control fume particulate.
  • Particulate filters will not protect workers from welding gases that may be contained within the fume.
  • Fit testing is required for RPE with a tight-fitting face seal (including disposable RPE).
  • Workers wearing tight-fitting RPE must be clean-shaven.
  • Workers should know how to fit and maintain tight-fitting RPE.
  • Disposable RPE should be discarded at the end of shift, or sooner if it becomes blocked with fume or dust.
  • RPE should be maintained in accordance with manufacturer guidelines.
  • Non-disposable RPE must be examined and thoroughly tested at least once every month.
  • A powered respirator is required to carry out welding for more than one hour per day.

Powered respirators will generally provide better levels of protection to workers and will include other integrated protection measures such as an auto-darkening welding visor which protects the operator’s eyes and skin from UV radiation.

Additional guidance on RPE can be found within the HSE publication at the following link:

General ventilation

In addition to LEV and RPE, employers should also consider the provision of effective general ventilation. General ventilation is an important consideration where other employees may be exposed to welding fume within the work area. In most welding workshops mechanical general ventilation will be required as natural ventilation from doors and windows will not be sufficient to disperse any fume that has not been removed by LEV.

Mechanical general ventilation typically consists of high level fans to extract air and draw in clean area to disperse airborne contaminants.

In some cases good levels of general ventilation may be sufficient to adequately control exposure to welding fume e.g. for sporadic or occasional low intensity resistance spot welding and tungsten inert gas (TIG) welding.

Sporadic welding is occasional welding carried out less than once per week which is incidental to the business core activity and cannot be planned e.g. repair or maintenance work.

Low-intensity welding is considered to be welding practices lasting less than 1 hour per welder per shift.

Health Surveillance

Respiratory health surveillance is likely to be necessary when welding stainless steel which contains known asthmagens such as hexavalent chromium and nickel. Where an employer’s risk assessment identifies such a risk, health surveillance should be provided for affected workers.

Health surveillance for occupational asthma should only be undertaken by a competent occupational health provider. Further guidance on health surveillance can be found within the document at the following link:

Cutting and surface preparation

A range of other allied processes such as oxy-gas cutting and plasma arc cutting also generate fume which can result in a range of ill-health conditions similar to those caused by exposure to welding fume. Further guidance on cutting processes and surface preparation techniques are available by selecting Welding COSHH essentials sheets within the resources section.

Prevent breathing in dangerous fumes during welding

Exposure to welding fume can cause a range of serious health effects including lung cancer, so you must put controls in place.

The video at the link below shows how to prevent breathing in dangerous fumes during welding:


Key legislation

Please note that this link is to the original legislation, visitors should verify for themselves whether legislation is in force or whether it has been amended or repealed by subsequent legislation.