When is air monitoring needed?

Air monitoring and measurement may be needed where there is a serious risk to health from the inhalation of welding fume and the likely exposure level of the welders to the fume is not known, e.g. during the manual metal arc (MMA) welding of stainless steel.

Monitoring may also be needed to help confirm that the control measures in use are working correctly, as a deterioration or failure of engineering controls could result in welders being exposed to high levels of fume.

Under the Control of Substances Hazardous to Health (COSHH) system, an initial exploratory exposure monitoring exercise may be needed to reach an accurate judgement about the risk to health. The results will then influence the assessment of how well control measures for the welding fume are working. The investigation will also need to look at other factors that can influence exposure on the day, such as the production rate setting the amount of welding work needed. These things will influence the personal results of the survey for exposure to welding fume.

It is wise to conduct air monitoring when:

• welding coated material, eg galvanised steel
• using metals which have low exposure limits, such as nickel and chromium
• fume is seen in the air coming away from the welding process
• fume is seen which isn’t being captured by the existing extraction
• there are concerns about the performance of the existing control measures
• you want to gather information which will help specify further control measures.

Why do I need air monitoring?

The monitoring information can be used to:

• help to inform the COSHH assessment for the task as it gives an illustration of the exposure risk
• help to select the right fume control solutions
• check that exposure limits are not exceeded
• check that controls work well enough, or if improvements are needed
• check that new controls work well enough
• help choose the right level of respiratory protection
• influence the health surveillance programme.

The COSHH Regulations require employers to:

• assess the risks to health from hazardous substances such as welding fume (regulation 6)
• adequately control the risk to health (regulation 7)
• maintain, examine and check controls (regulation 9)
• provide health surveillance where appropriate (regulation 11).

Regulation 12 of COSHH also requires employers to inform,
instruct and train workers who are exposed to welding fume on:

• the health risks
• how to report any ill health symptoms
• how to use controls to prevent ill health occurring.

The Control of Lead at Work (CLAW) Regulations 2002
require employers to:

• assess the risk from welding and allied processes which result in exposure to lead dust and fumes, eg from lead-based paint on metal (regulation 5)
• prevent or control exposure to lead (regulation 6)
• maintain, examine and check controls (regulation 8)
• carry out air monitoring where there is likely to be significant exposure to lead (regulation 9)
• provide medical surveillance(regulation 10).

Air monitoring is a specialist activity. A qualified occupational hygienist can ensure it is carried out in a way that provides meaningful and helpful results.

Personal air monitoring results can be compared with the relevant set workplace exposure limits (WELs) which are published in the HSE book EH40/2005: Workplace Exposure Limits In-house limits can also be set and used to compare with results for task-specific exposures. There is no single WEL for welding fume. Therefore, exposure measurements should be compared to the appropriate limits for the different constituents in the welding fume, such as: iron oxide, hexavalent chromium, nickel and manganese. Hexavalent chromium and nickel in welding fume are both defined occupational carcinogens. This means that there is a requirement to reduce exposure to these constituents to a concentration which is as low as is reasonably practicable (ALARP). For other substances which have a WEL but are not carcinogens or can cause asthma, adequate control of exposure will involve controlling exposure to below the WEL.

Any revised WEL, which might be implemented, will require improved fume control measures for many welding processes.

Biological monitoring can also be used for investigating the extent of exposure following a report of ill health.

Biological monitoring for stainless steel welders should include the measurement of nickel and chromium in a urine sample and this should be undertaken on an annual basis where control has been shown to be good. Samples should be collected at the end of a typical working week.

Biological monitoring can also be used for exposure measurement for other metal fumes, including, for example; cadmium or lead, which should be measured if the metal has been cadmium plated or if lead paint (lead oxide primer) is present. To determine recent exposure to cadmium or lead, a blood sample will be required. The table below sets out the recommended biological monitoring analytical method for various metal types.

Employees cannot be compelled to provide biological monitoring samples without consent. Biological monitoring is a specialist activity. Urine samples are usually collected by either an occupational hygienist (www.bohs.org ), or occupational health professional (doctor or nurse) (www.som.org.uk ). The samples are then sent to a specialist laboratory (www.hsl.gov.uk ) for analysis by post.