Knowledge Centre


Welding Fumes - The Complete Guide


With up to 80,000 known Welders in the UK, including those that use welding techniques as part of their positions, a big proportion of the population come face to face with potential harmful fumes and gases every single day. The fume given off by welding processes is a varying mixture of airborne gases and very fine metal particles.

Typical industries that use welding processes are Manufacturing, Construction, Fabrication and Engineering. Individuals working alongside welders in warehouses, factories or other confined spaces could also be putting their health at risk.

Exposure risk increases depending on the type of welding technique being used and the metal being welded. However, recent evidence suggests that welding mild steel can lead to increased levels of cancer even though this has always been considered as low risk.  As a result of this new evidence, the HSE strengthened its enforcement expectations in 2019.

The following information will help companies involved with welding practices, including Health and Safety mangers and other key decision makers, to decide if additional ventilation, fume extraction or respiratory protective equipment (RPE) is required or adequate in the workplace.

What are welding fumes?

The fume given off by welding processes includes a varying mixture of airborne gases (predominantly Nitrous Oxide and Ozone) and very fine particles. The visible part of the fume cloud is mainly particles of metal, metal oxide and flux (if used).

How to assess the level of risk?

The exact level of risk from the fume will depend on three key factors:

  • How toxic the fume is;

  • How concentrated the fume is;

  • How long employees breathe in the fume in question.

Let’s consider how much time is spent ‘on the job’ – some welders, particularly fabricators, spend a significant amount of time setting up a job before they pick up the welding torch to start welding. This means in an eight-hour working day, the welder may only actually weld for an hour or two. Conversely, a production welder who is supplied with ready cut parts and a jig to hold them will spend much more time welding.

When you are assessing risk, it is important to consider how long a welder will be welding so an accurate assessment of exposure can be calculated.

What are the health effects?

Some welders may never fall ill from breathing in welding fume whilst others may get permanent illnesses.

If your workforce regularly breathes in welding fume, you could be putting them at risk of developing asthma, pneumonia, occupational asthma, cancer, metal fume fever, irritation of the throat and lungs or temporary reduced lung function.

What are the exposure limits?

The exposure limits (WELs) as defined by the HSE for each of the common substances are as follows:

Aluminum 10mg/m3, Arsenic 0.1mg/m3, Chromium 0.5mg/m3, Copper 0.2mg/m3, Iron 5mg/m3, Lead 0.15mg/m3, Manganese 0.2mg/m3, Nickel 0.1mg/m3, Titanium 10mg/m3, Ozone (STEL) 04mg/m3, Nitrogen Oxide 2.5mg/m3

The list is not exhaustive and there are many more substances that could be present in the fume.

All of the WELs are based on an average 8 hour exposure period. Thus, a welder exposed to a relative high concentration of fume for a short period of the day may in fact have a low exposure when averaged out over a full working day.

However, certain substances have been assigned a short term exposure limit (STEL) which must be considered when averaging exposure times. For example, exposure to ozone and iron etc must not exceed the STEL over any 10 minute period.

The WELs and STELs provide the legal limits that should never be exceeded, but there is an expectation that organisations should aim to keep exposure below 10% of these limits.

Exposure monitoring strategies

The exposure monitoring strategy and substances tested will vary according to the welding technique being used and the metals being worked upon. If we take a welder using MIG on mild steel, the likelihood of exposure to gases is low and the main focus of any monitoring strategy would be a range of typical metal particulates. For many other welding techniques (MMA, TIG and Flame based) and Aluminum welding, it is necessary to test for exposure to the gases.

The highly toxic substance, Hexavalent Chromium VI, is rarely considered. Hexavalent Chromium VI is generated when stainless steel is welded using MMA and has an exposure limit of only 0.05mg/m3 which is 10 times lower than standard Chromium. This should not be overlooked when reviewing risk and planning a monitoring strategy.

To ensure any monitoring is representative you are expected to carryout exposure monitoring to a minimum of 20% of the workforce   carrying out a particular activity or welding technique.

Frequency of exposure monitoring?

The HSE does not stipulate a set timeframe for the frequency that exposure monitoring should be carried out, they simply state that it should be carried out regularly.

How often you carry out monitoring will depend on the risk and a number of other factors, including:

  • The range of welding techniques used and frequency;

  • The results of previous exposure monitoring exercises;

  • Environmental conditions (humidity levels, air movement etc);

  • Variances in technique from one operative to another;

  • Variances in workloads;

  • Changes in engineering controls.

For example, if you carry out an assessment once a year, the typical 1 day assessment must represent exposure over the 365 days in that year.

The aim of exposure monitoring is to build up a bank of data which covers a range of different conditions and scenarios so that you can be confident the risk is being adequately controlled.

Do I need engineering controls & RPE?

Control of cancer and other health risks will require suitable engineering controls for all indoor welding activities, such as local exhaust ventilation (LEV).

Where LEV does not adequately control exposure, it should be supplemented by adequate and suitable respiratory protective equipment (RPE) to protect against the residual fume.

Furthermore, appropriate RPE should be provided for outdoor welding. You should ensure welders are suitably instructed and trained in the use of these controls.

Regardless of duration, the HSE now requires that suitable exposure control measures should be in place for any welding because there is no known level of safe exposure.

Risk assessments should reflect the change in the expected control measures. Actions required are as follows:

  • Make sure exposure to any welding fume released is adequately controlled using engineering controls (typically LEV);

  • Make sure suitable controls are provided for all welding activities, irrelevant of duration. This includes welding outdoors;

  • Where engineering controls alone cannot control exposure, adequate and suitable RPE should be provided to control risk from any residual fume;

  • Make sure all engineering controls are correctly used, suitably maintained and are subject to thorough examination and test where required;

  • Make sure any RPE is subject to an RPE programme.

Other ways of reducing the risk

The first step in the process is to carry out a risk assessment by identifying what welding activities are being carried out on your site, including the range of welding techniques used and metal combinations.

The next step should be to commission a series of actual personal exposure assessments which cover the full range of activities. Depending on the exposure levels, it may be necessary to install some form of extraction system or respiratory protection which is adequate to cover the type of exposure likely from the welding activities.

Ask yourself the following questions:

  1. Can the job be designed so there is less ‘hot work’ including welding processes?

  2. Can the manufacturing sequence or techniques be modified so there is less ‘hot work’?

  3. Can you use a welding technique that makes less fume?

  4. Are your welders using the optimum setup?

  5. Can you reduce the amount of time your welders are welding?

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