How Are Welding Fumes Produced?

During welding and other hot metalworking activities, extremely high temperatures can cause metal from the workpiece, welding consumable or surface coating to vaporise.

As the hot metal vapour cools, it reacts with oxygen and condenses into extremely small solid particles. These airborne particles are known as welding fume.

Welding and cutting processes can also produce hazardous gases. The resulting airborne contamination may therefore include:

• Fine and ultrafine metal particles
• Metal oxides
• Fumes from welding rods, wires and fluxes
• Contaminants released from paints, plating and other coatings
• Gases produced by the welding arc or flame

What Do Welding Fumes Contain?

The composition of welding fumes depends on several factors, including:

• The welding or cutting process
• The base metal being worked on
• The welding rod, wire, flux or other consumable
• Paint, plating or other surface coatings
• Oils, solvents and surface contamination
• The temperature and welding settings
• Shielding gases and surrounding air

Depending on the materials and process, welding fumes may contain substances such as:

• Iron oxides
• Manganese
• Chromium, including hexavalent chromium
• Nickel
• Cobalt
• Zinc oxide
• Copper compounds
• Lead or cadmium in certain materials or coatings

The welding consumable may contribute more to the fume than the base metal. Employers must therefore assess the workpiece, coatings and consumables when determining the risks.

Hazardous Gases Produced During Welding

Welding and thermal cutting can produce gases as well as metal particles. Depending on the process and working conditions, these may include:

• Ozone
• Nitrogen oxides
• Carbon monoxide
• Gases released by heated paints, solvents and coatings
• Shielding gases that may displace oxygen

Some welding gases can irritate or damage the lungs. Others may cause headaches, dizziness, unconsciousness or asphyxiation, particularly if they accumulate within an enclosed or confined space.

All Welding Fumes Can Cause Cancer

All welding fumes can cause lung cancer and may cause kidney cancer. Welding fume is classified as carcinogenic to humans, and this includes fumes produced when welding mild steel.

Exposure must be prevented or adequately controlled during every welding activity, regardless of:

• The type of metal being welded
• The welding process being used
• Whether the work takes place indoors or outdoors
• Whether the fume can be seen or smelled
• How long the welding task takes

A short welding task is not a fume-free or risk-free task. Suitable controls must be in place before work begins.

Why Welding Fumes May Be Difficult to Detect

Welding fumes are not always clearly visible. Some particles and gases may be present even when there is no obvious cloud of fume.

Workers must not rely on sight or smell to decide whether an atmosphere is safe. The absence of visible fume does not mean that exposure is adequately controlled.

Air currents can also move contamination away from the weld and into other parts of the workplace, potentially exposing people who are not directly involved in the welding activity.

How Welding-Fume Particles Enter the Body

Welding-fume particles are small enough to be inhaled into the respiratory system. The finest particles can travel deep into the lungs, where they may cause inflammation, damage lung tissue or enter the bloodstream.

Depending on their composition, welding fumes can cause:

• Metal fume fever
• Irritation of the throat and lungs
• Occupational asthma
• Pneumococcal pneumonia
• Reduced lung function
• Chronic respiratory disease
• Neurological effects from substances such as manganese
• Lung cancer

The Legal Requirement to Control Welding Fumes

Welding fumes are substances hazardous to health and are regulated under the Control of Substances Hazardous to Health Regulations 2002 (COSHH).

Employers must assess the risks and prevent exposure where reasonably practicable. Where prevention is not reasonably practicable, exposure must be adequately controlled.

Suitable measures may include:

• Using an alternative joining method
• Selecting a lower-fume welding process
• Using suitable local exhaust ventilation
• Providing adequate general ventilation
• Providing suitable respiratory protective equipment where required
• Maintaining and testing exposure-control equipment
• Providing information, instruction, training and supervision

Key Facts About Welding Fumes

• Welding fumes are formed when vaporised metal cools and condenses into fine particles.
• Fume may come from the workpiece, consumable, flux or surface coating.
• Welding can also produce hazardous gases.
• The exact composition depends on the process and materials involved.
• Welding fumes may be present even when they cannot be clearly seen.
• Fine particles can be inhaled deep into the lungs.
• All welding fumes can cause lung cancer.
• Every welding activity requires suitable exposure controls.