Following The Health and Safety Executive (HSE)’s recent introduction of restrictions on hazardous welding fumes, businesses can expect greater scrutiny regarding the effectiveness of existing controls on welding activities. Here, Scott Clark, Principal Occupational Hygiene Consultant at Bureau Veritas, explains how firms can update their risk assessments to reflect the change in control measures.

In February 2019, the HSE released a Safety Alert (STSU1 – 2019) targeted at any persons responsible for, or undertaking, welding activities, including Mild Steel welding.

The alert has reclassified the status of all welding fume as a Group 1 carcinogen – cancer-causing to humans following new scientific evidence from the International Agency for Research on Cancer linking exposure to lung cancer and potentially kidney cancer.

Welding activities can generate various hazardous components including fume, gases, vapours and ultraviolet (UV) radiation; all of which present health risks. As well as welding fume being recognised as cancer-causing, other health effects of exposure have long been known to include metal fume fever, serious lung conditions and neurological effects linked to Manganese (Mn), a chemical present in mild steel welding fume.

The tougher stance on welding activities follows the introduction last year of the EH40/2005 Workplace Exposure Limits guidance by the Hazards to Respiration HSE, setting out new and revised workplace exposure limits (WELs) for 31 chemical substances, including new exposure limits for Mn in both inhalable and respirable fractions – raising the significance of Mn as a component of welding fume.

The restrictions represent a significant change for industries where welding forms an integral part of the manufacturing process and where a company needs to maintain structure and asset integrity of their plant or production lines. This will affect many businesses including those operating in the automotive, engineering, chemical, construction, petrochemical and pharmaceutical sectors.

The safety alert was unambiguous in specifying that there will be a strengthening of HSE’s enforcement expectation for all welding fume because current control methods such as general ventilation on its own will not be deemed acceptable in achieving adequate control.

“following this reclassification there is now no known level of safe exposure to welding fume”

Following this reclassification there is now no known level of safe exposure to welding fume and businesses can expect greater scrutiny regarding the effectiveness of engineering controls. It also means that where controls are not adequate or not present – for example when welding outside – that appropriate and effective respiratory protective equipment (RPE) is provided and used. This will include training for workers to ensure compliance.

There is now an expectation that due to the carcinogenic risk, that all indoor welding activities will require Local Exhaust Ventilation (LEV). Where the LEV does not adequately control exposure, it should be supplemented by adequate and suitable RPE to protect against any residual fume not captured by the LEV. Best practice It is worth noting that there should be nothing new in this approach, certainly within the UK. Adequate control of exposure requires employers to apply the eight principles of good practice outlined in the Control of Substances Hazardous to Health (COSHH) Regulations Schedule 2A.

They must also ensure the WEL is not exceeded and that exposure to substances that can cause occupational asthma cancer, or damage to genes that can be passed from one generation to another is reduced as low as is reasonably practicable.

In addition, welders may now require medical screening prior to employment to identify any preexisting conditions. Although it is not a mandatory requirement, many reputable firms already have this in place as a matter of best practice.


The HSE will also expect organisations to have up-to-date and adequate risk assessments in place which reflect the increased risk posed by this update. All employers are therefore advised to review their COSHH risk assessments for welding activities and revise where necessary their control measures to protect those undertaking welding activities.

This may include introducing workplace exposure monitoring to properly assess the risk. Noncompliance will not only pose a significant safety hazard to workers, but will mean that businesses leave themselves open for severe repercussions from the HSE.

The requirement to follow good occupational hygiene practice is explicitly referenced in the COSHH Regulations 2002, Schedule 2A, including:

  • Design and operate processes and activities to minimise emission, release and spread of substances hazardous to health
  • Take into account all relevant routes of exposure-inhalation, skin absorption and ingestion when developing control measures
  • Control exposure by measures that are proportionate to the health risk
  • Choose the most effective and reliable control options which minimise the escape and spread of substances hazardous to health
  • Where adequate control of exposure cannot be achieved by other means, provide, in combination with other control measures, suitable protective equipment
  • Check and review regularly all elements of control measures for their continuing effectiveness
  • Inform and train all employees on the hazards and risks from the substances with which they work and the use of control measures developed to minimise the risks
  • Ensure that the introduction of control measures does not increase the overall risk to health and safety

Control measures

For all welding activities the following three control measures should be considered for implementation:

  1. Local Exhaust Ventilation (LEV)
  2. Respiratory Protection Equipment (RPE)
  3. General ventilation

In practice, adequate control should be able to be demonstrated by using a combination of all three. Dependent on individual circumstances and design, one control measure alone will probably not be deemed adequate to demonstrate effective control. It is therefore recommended that an approach adopting all three control measures combined be considered.

The successful combination of these three components will contribute to reducing exposures to as low as reasonably practicable (ALARP); however, the success of each will be dependent on a range of factors.

Local Exhaust Ventilation (LEV)

As one of the most effective engineering control measures, LEV is usually installed to capture the weld fume as close as possible to the source and should be viewed as the primary control measure, where it is feasible to introduce.

LEV systems suitable for welding can either be fixed (e.g. in a workshop) or portable (mobile units). Both types of system should be supplied with a large enough captor hood to aid the capture of the weld plume, with a flexi/hard duct configuration to transport the captured fume through to a motor/fan unit with a filtration unit to clean the air.

Ideally, the LEV extract fan and discharge stack should be sited outside, and exhausted to atmosphere, to minimise the recirculation of air back into the workplace and prevent the inadvertent re-introduction of contaminated air, in the event of failure of the LEV performance. The captor hood is to be placed as close to the weld fume source as possible and ideally directly above it to promote effective capture (as weld plume naturally rises).

Whether a fixed or portable unit is used also depends on the type of welding activity. For instance, dynamic processes such as pipe fitting that involves welding will require a portable device that can move locations along with the welder as works progress.

Many businesses will no doubt conduct feasibility tests before installing LEV devices to determine the cost-effectiveness and ease of installation. However, it’s also important to take into account how it can address the risk of exposure.

Fine Dust Filter/ HEPA Filter

There are several variants of portable LEV units on the market that provide a good, less expensive alternative to fixed systems which invariably cost more. Some portable LEV units are fitted with a fine dust filter, some are fitted with a High Efficiency Particulate Air (HEPA) filter. Ideally a recirculating LEV device, such as a portable LEV unit which exhausts air back into the working environment, should be fitted with a HEPA filter (to capture particulate) and charcoal filters (to adsorb certain gases/vapours). It should also be able to successfully meet the requirements of a HEPA Filter Installation Leak Test (“DOP”) e.g. similar to a Type (Class) H vacuum used in the asbestos industry.

The advantage of these type of devices is that the HEPA filter, seal and carcass/body of the filter compartment will be challenged during the test to ensure its integrity has not been compromised and is thus a test which can be repeated to promote consistency during LEV assessments. It is worth noting that in HSG258 Controlling Airborne Contaminants at Work – A guide to local exhaust ventilation (LEV) and where HEPA filters are fitted that “an appropriate European or ISO standard is used to test such filter in situ” e.g. ISO 14664-3. The disadvantage of an LEV system which doesn’t house or accept a HEPA filter is that it’s not possible to perform a suitable repeatable test on the device, and thus only a visual inspection can realistically be adopted.

As there is no known safe level of exposure, it is deemed more beneficial to utilise systems whereby if air has to be returned back to the workplace from the LEV system that it is fitted with a HEPA filter. However, it is not yet known if the HSE will expect recirculating LEV devices used to capture welding fume to meet such requirements.

Note: to ensure the ongoing effectiveness of LEV systems, they must be assessed and inspected every 14 months.


Where previously RPE wasn’t mandatory for mild steel welding activities, the HSE’s recent restrictions have certainly made it so. Unless all weld fume produced can be effectively controlled without the need for RPE, then RPE will still be deemed necessary. This is due to the likelihood that not all the welding plume will be effectively captured at source, but this will be dependent on the process. For instance, a fairly static, routine welding operation will be more easily controlled in a permanent fixed location than a welding operation being performed out on site.

The type of RPE to be used will be based on suitability for the working environment, operator comfort and cost. As the HSE alert states, where adequate control cannot be relied upon by LEV, then RPE will be required.

Positive pressured RPE is usually the most effective option, with various designs to accommodate the requirements of a welder. However, such equipment can often be more expensive and harder to maintain, resulting in a reluctance to adopt them. It is important to note that given the expected rise in the use of RPE devices, the user is required to be clean shaven when wearing tightfitting masks/respirators to ensure a sufficient seal is created and the user must be face fit tested for the type of mask in use. In addition, tight fitting masks can be uncomfortable to wear for continuous periods leading to an increased chance of exposure if they are adjusted in the working environment.

As there is no known safe level of control, and it is dependent on exposure scenarios and duration of exposure, it is deemed most likely that Powered Air Purifying Respirators (PAPRs) will be used more and more. These usually come in the form of a waist or backpack mounted unit, integrated with particulate and gas/vapour filters that clean the air prior to entering the wearer’s welding hood.

The advantage of these types of devices is that they provide greater protection against particulates, gases and vapours than a tight-fitting face mask and are easier to wear. However, tight-fitting masks/respirators may still be beneficial, and possibly preferred, where access around the workspace is limited and results in welders having to navigate and weld in tight, restricted areas (e.g. when welding structural steel on site).

General ventilation

In light of the HSE’s recent announcement, there’s now a greater onus for businesses conducting welding activities to assess current control strategies. General ventilation can still support good control when in combination with LEV and RPE.

First and foremost, it is important to establish and quantify what general ventilation is already in place.

Is it just passive ventilation or are other forced mechanical systems in place? General ventilation should be viewed as the tertiary requirement, and although placed beneath LEV and RPE in importance, it is still deemed necessary to incorporate the introduction of fresh-air through a working environment where the work space is enclosed, e.g. workshop or temporary welding habitat (including habitats erected outside).

When performed outdoors, managing welding fume exposure is certainly much harder to control as the plume is difficult to effectively capture, particularly in restrictive spaces where it can be hard to install an LEV device. Other safety aspects must also be considered. For example, if the welding process is taking place in a high-risk environment such as a chemical plant then care must be taken to ensure that sparks generated are contained/controlled. In such cases, enclosing the welding process and providing controlled general ventilation (dilution ventilation) may be the best form of control of weld fume when combined with RPE. In the oil and gas industries, temporary habitats – with supply (fresh-air) and extraction ventilation systems – are used to isolate the welding process from the immediate area and create a positive pressure environment to reduce the migration of hazardous gases/vapour into the welding area from outside.

The introduction of fresh-air ventilation throughout a working environment will serve to dilute the contaminated air which hasn’t been captured at source by the LEV, and thus reduce the potential for exposure not only of the welding personnel, but also to reduce inadvertent exposure of others. It will also serve to dilute air which is being returned to the working environment via a recirculation LEV device and further help to reduce exposure to fume, particulate, gases and vapours which aren’t captured.

Indeed, grey areas may arise with regard to dynamic processes where secondary exposure to welding fume can be difficult to control. An example of this would be where a welder is tasked with fitting a pipe in a facility which sees the welding activity move from one place to another, further complicated by visitors entering and leaving the workspace. In such instances, as there is now no safe level of exposure, businesses must assess what is the risk to populations/exposure groups that aren’t directly involved in the welding activity but may still be exposed. Therefore, effective general ventilation cannot be overlooked.

A step ahead

Amid the tighter WELs restrictions, it is an appropriate time for industries that utilise welding to get much tougher on minimising the dangers that welding fumes pose to employee health. At the heart of this will be ensuring businesses have a robust occupational hygiene strategy in place for controlling workplace exposure to harmful substances, which if done correctly can not only prevent ill health but can also reduce the reliance on uncomfortable respiratory protective equipment, thus improving working conditions.

As a global health and safety and compliance expert, Bureau Veritas is ideally placed to provide a holistic support service to organisations undertaking welding activities. This includes assessment of welding qualifications, audit and assessment of welding processes, thorough examination and test of local exhaust ventilation (LEV) systems, measurement and monitoring of welding fume exposure, review and update of COSHH risk assessments and provision of advice on appropriate engineering controls.


  1. TheSynergist/Industry%20News/Pages/ IARC-Welding-Fumes-UV-Radiation-fromWelding-Are-Carcinogenic.aspx
Welding helmet handing in workshop on white background. Welder protective helmet inside