Controlling welding fumes, gases in the workplace

The control of fumes and gases in arc welding is an important workplace health and safety issue. Fortunately, many solutions are available to improve fume control, providing users with a number of options to comply with applicable exposure limits. Before selecting a solution, however, users need to evaluate each individual application to determine the best control method.

By Christopher J. Cole, The Lincoln Electric Company September 15, 2007

The control of fumes and gases in arc welding is an important workplace health and safety issue. Fortunately, many solutions are available to improve fume control, providing users with a number of options to comply with applicable exposure limits. Before selecting a solution, however, users need to evaluate each individual application to determine the best control method.

The first step is to identify welding fume exposures and related potential hazards. This involves a review of information, such as Material Safety Data Sheets, about the materials and processes in the workplace. Next, evaluate the welding fume exposures and take air samples to quantify worker exposures. Compare the exposures to the applicable exposure limits, such as OSHA’s permissible exposure limits or the American Conference of Governmental Industrial Hygienists’ threshold limit values, to identify and prioritize those in which improvement is needed. The final step is to assess available control methods and determine which solutions are best for the application. No single solution will fit all applications, and more than one control method may be needed in some cases.

Engineering controls

Changes in the manufacturing process and ventilation system can be used to control the fume generated. Welding processes, procedures and shielding gases or consumables can be modified to reduce the amount of fume generated. The fume generated per amount of deposited weld metal varies from one process to another. Process changes may reduce the amount of fume generated, but in most cases the application will still require ventilation to control exposures.

Changing to a different arc welding process may reduce fume generation. For example, gas tungsten arc welding or submerged arc welding processes produce very low fume levels, but they have significant process limitations. Gas metal arc welding (GMAW) is also a relatively low fume-generation process that may have fewer limitations. Welding equipment designed to produce a modified GMAW waveform, such as pulsed GMAW, Waveform Control Technology or Surface Tension Transfer, may also reduce fume generation rates.

In general, the change to a different arc welding shielding gas for gas-shielded welding processes — GMAW or gas-shielded, flux-cored arc welding — may reduce fume generation rates. The fume generation rate may be reduced by changing from CO2-based shielding gases to Argon, Ar/CO2, Ar/O2 or other gas mixtures such as 95-5 Ar/O2. Such a change also has an effect upon welding characteristics, and if the application can accommodate such a change, a reduction in fume generation rate is possible.

Welding procedures can also have an impact on fume generation rates. In general, lower welding output results in lower fume generation rates. Changing the consumable being used may also reduce the amount or makeup of the fume being generated. Testing may be needed to determine the best procedure for an application.

Other options to control fume

Each of the methods mentioned above can be a part of the solution for a specific application, but each also has limitations, such as low penetration or difficulty in welding in some positions, which must be considered. Other procedures can alleviate these limitations.

Isolation is a possible approach to reduce worker exposure by separating, enclosing or automating the fume source. Consider whether it is practical to implement an automatic welding process using hard automation or robotic welding equipment that can be enclosed.

Ventilation is the most flexible solution because it does not require a change in arc welding procedure, and it affords a range of methods that can be used to control welding fume. Ventilation methods include natural ventilation, general mechanical ventilation and local exhaust.

Natural ventilation relies upon wind or airflow through a workspace and is less controllable; however, it can be a good solution in applications where welding is done outside or in large work areas with high ceilings and cross ventilation.

General mechanical ventilation, such as wall or roof exhaust fans, provides general fume removal but is less effective than local exhaust in the control of individual exposures. If natural and general ventilation is not sufficient to control fume exposure levels, then local exhaust at the welding arc should be considered. Local exhaust is a very effective alternative for most welding exposures where better control is needed. Some welding consumables that contain amounts of substances with low exposure limits — stainless with chromium and hardfacing with chromium or manganese, for example — may require additional ventilation and/or exhaust. Review product labeling and MSDS to identify such products.

Low and high-vacuum systems are two general types of local exhaust systems. Low-vacuum systems extract fume at a low velocity but at a high volume and are effective from 6 to 15 inches from the weld source. Low-vacuum systems are available in mobile or stationary configurations, generally include flexible arms and consume less energy and produce less noise than their high-vacuum counterparts.

High-vacuum systems operate at high velocity, but they extract low volumes of air. Typically positioned between 2 to 4 inches from the source of welding fume plume, their effectiveness depends on the welder making adjustments as necessary to maintain a close position between the arc and the nozzle. High-vacuum systems are also available in mobile or stationary configurations and use suction nozzles or fume extraction guns. High-vacuum systems are flexible and adapt to large workpieces or confined spaces.

Safe work practice controls

Operator work practices are an essential component in the effective use of engineering controls to maintain a safe workplace. Ensuring that safe operating practices are consistently followed in the workplace should be a part of any solution to control welding fume exposure, as well as to minimize worker exposure to other hazards. Key principles for safe work practices include:

Welders should be trained to keep their head out of the fumes

Welders should use enough ventilation or exhaust at the arc, or both, and keep fumes and gases from their breathing zone and general area

Welders should be trained to properly use ventilation and exhaust equipment

Welders should read and follow product warnings, MSDS and the employer’s safety rules.

These common sense precautions are known to trained welders. However, reinforcing them with periodic training is essential. Many welding product manufacturers can assist employers by providing training or materials.

Personal protection equipment

Personal protection equipment (PPE), such as respirators, is the most difficult control method to effectively implement, and OSHA requires that practical and feasible engineering controls and work practices be implemented before relying on it. In situations where the use of a respirator is necessary, OSHA requires employers to establish a respiratory protection program (29CFR 1910.134).

When undertaking any program to control welding fume exposures, no solution will fit every application. The final approach will likely include a combination of methods, dictated by the requirements of the application and user preferences. Any solution should result in acceptable welding quality and productivity and achieve a workplace compliant with applicable exposure limits and a cleaner working environment.

Author Information

Christopher J. Cole, MS, CIH, CSP is welding health and safety coordinator, Automation Division, The Lincoln Electric Company.

For further information…

For further information on controlling welding fumes, see American Welding Society publications such as ANSI/AWS Z49.1 “Safety in Welding, Cutting and Allied Processes,” which can be downloaded at