Welders, welding operators, and other persons in the area must be protected from overexposure to fumes and gases produced during welding, brazing, soldering, and cutting. Overexposure is exposure that is hazardous to health, and exceeds the permissible limits specified by a government agency. Such recognized authorities arethe U.S. Department of Labor, Occupational Safety and Health Administration (OSHA), Regulations 29 CFR 1910.1000; the American Conference of Governmental Industrial Hygienists (ACGIH) in its publications Threshold Limit Values for Chemical Substances and Physical Agents in the Workroom Environment. Persons with special health problems may have unusual sensitivity that requires even more stringent protection.

Fumes and gases are usually a greater concern in arc welding than in oxyfuel gas welding, cutting, or brazing because a welding arc may generate a larger volume of fume and gas, and greater varieties of materials are usually involved.

Protection from excess exposure is usually accomplished by ventilation. Where exposure would exceed permissible limits with available ventilation, respiratory protection must be used. Protection must be provided not only for the welding and cutting personnel but also for other persons in the area.

Refer to Industrial Ventilation, A Manual of Recommended Practice, Cincinnati: American Conlference of Governmental Industrial Hygienists (latest edition).

Arc Welding- Fumes and gases from arc welding and cutting cannot be classified simply. Their composition and quantity depend on the base metal composition; the process and consumables used; coatings on the work, such as paint, galvanizing, or plating; contaminants in the atmosphere, such as halogenated hydrocarbon vapors from cleaning and degreasing activities; and other factors.

Various gases are generated during welding. Some are a product of the decomposition of fluxes and electrode coatings. Others are formed by the action of arc heat or ultraviolet radiation emitted by the arc on atmospheric constituents and contaminants. Potentially hazardous gases include carbon monoxide, oxides of nitrogen, ozone, and phosgene or other decomposition products of chlorinated hydrocarbons, such as phosgene.

Helium and argon, although chemically inert and nontoxic, are simple asphyxiants, and could dilute the atmospheric oxygen concentration to potentially harmful low levels. Carbon dioxide (COz) and nitrogen can also cause asphyxiation.

Ozone may be generated by ultraviolet radiation from welding arcs. This is particularly true with gas shielded arcs, especially when argon is used. Photochemical reactions between ultraviolet radiation and chlorinated hydrocarbons result in the production of phosgene and other decomposition products.

Exposure Factors- The single most important factor influencing exposure to fume is the position of the welder’s head with respect to the fume plume. When the head is in such a position that the fume envelops the face or helmet, exposure levels can be very high. Therefore, welders must be trained to keep their heads to one side of the fume plume. In some cases, the work can be positioned so the fume plume rises to one side.

Ventilation- Ventilation has a significant influence on the amount of fumes in the work area, and hence the welder’s exposure. Ventilation may be local, where the fumes are extracted near the point of welding, or general, where the shop air is changed or filtered. The appropriate type will depend on the welding process, the material being welded, and other shop conditions. Adequate ventilation is necessary to keep the welder’s exposure to fumes and gases within safe limits.

The bulk of fume generated during welding and cutting consists of small particles that remain suspended in the atmosphere for a considerable time. As a result, fume concentration in a closed area can build up over time, as can the concentration of any gases evolved or used in the process. The particles eventually settle on the walls and floor, but the settling rate is low compared to the generation rate of the welding or cutting processes. Therefore, fume concentration must be controlled by ventilation.

Adequate ventilation is the key to control of fumes and gases in the welding environments. Natural, mechanical, or respirator ventilation must be provided for all welding, cutting, brazing, and related operations. The ventilation must ensure that concentrations of hazardous airborne contaminants are maintained below recommended levels. These levels must be no higher than the allowable levels specified by the U.S. Occupational Safety and Health Administration or other applicable authorities.

Respiratory Protective Equipment- Where natural or mechanical ventilation is not adequate or where protection from toxic materials require a supplement to ventilation, respiratory protective equipment must be used. Respirators with air lines, or face masks that give protection against all contaminants are generally preferred. Air-supplied welding helmets are also available commercially. Filter-type respirators, approved by the U.S. Bureau of Mines for metal fume, give adequate protection against particulate contaminants that are less toxic than lead, provided they are used and maintained correctly. Their general use is not recommended, however, because of the difficulty in assuring proper use and maintenance. They will not protect against mercury vapor, carbon monoxide, or nitrogen dioxide. For these hazards an air line respirator, hose mask, or gas mask is required.

Special Ventilation Situations

Welding in Confined Spaces- Special consideration must be given to the safety and health of welders and other workers in confined places. Gas cylinders must be located outside of the confined space to avoid pos sible contamination of the space with leaking gases or

volatile material. Welding power sources should also be located outside to reduce danger of engine exhaust and electric shock.

A means for removing persons quickly in case of emergency must be provided. Safety belts and lifelines, when used, should be attached to the worker’s body in a manner that avoids the possibility of the person becoming jammed in the exit. A trained helper should be stationed outside the confined space with a preplanned rescue procedure to be put into effect in case of emergency.

Welding of Containers- Welding or cutting on the outside or inside of containers or vessels that have held dangerous substances presents special hazards. Flammable or toxic vapors may be present, or may be generated by the applied heat. The immediate area outside and inside the container should be cleared of all obstacles and hazardous materials.

When repairing a container in place, entry of hazardous substances released from the floor or the soil beneath the container must be prevented. The required air-supplied respirators or hose masks are those accepted by the U.S. Bureau of Mines or other recognized agency. For more complete procedures, refer to AWS F4.1, Recommended Safe Practices for the Preparation for Welding and Cutting Containers that Have Held Hazardous Substances. Miami: American Welding Society (latest edition). When welding or cutting inside of vessels that have held dangerous materials, the precautions for confined spaces must also be observed.

Highly Toxic Materials- Certain materials which are sometimes present in consumables, base metals, coatings, or atmospheres for welding or cutting operations, have permissible exposure limits of 1.0 mg/m3 or less. Among such materials are the following metals and their compounds:

(1) Antimony

(2) Arsenic

(3) Barium

(4) Beryllium

(5) Cadmium

(6) Chromium

(7) Cobalt

(8) Copper

(9) Lead

(10) Manganese

(11) Mercury

(12) Nickel

(13) Selenium

(14) Silver

(15) Vanadium

Base metals and filler metals that may release some of these materials as fume during welding or cutting are shown in Table W-2.

Manufacturer’s Material Safety Data Sheets should be consulted to determine if any of these highly toxic materials are present in welding filler metals and fluxes being used. Material Safety Data Sheets should be requested from suppliers. However, welding filler metals and fluxes are not the only source of these materials. They may also be present in base metals, coatings, or other sources in the work area. Radioactive materials under Nuclear Regulatory Commission jurisdiction require special considerations.

When toxic materials are encountered as designated constituents in welding, brazing or cutting operations, special ventilation precautions must be takea to assure that the levels of these contaminants in the atmosphere are at or below the limits allowed for human exposure. All persons in the immediate vicinity of welding or cutting operations involving toxic materials must be similarly protected. Unless atmospheric tests under the most adverse conditions establish that exposure is within acceptable concentrations, the following precautions must be observed.

Confined Spaces- Whenever any toxic materials are encountered in confined space operations, local exhaust ventilation and respiratory protection must be used.

Indoors- When any toxic materials are encountered in indoor operations, local exhaust (mechanical) ventilation must be used. When beryllium is encountered, respiratory protection in addition to local exhaust ventilation is essential.

Outdoors- When any toxic materials are encountered in outdoor operations, respiratory protection approved by the Mine Safety and Health Association (MSHA) the National Institute of Occupational Safety and Health (NIOSH), or other approving, authority may be required.

Persons should not consume food in areas where fumes that contain materials with very low allowable exposure limits may be generated. They should also practice good personal hygiene, such as washing hands before touching food, to prevent ingestion of toxic contaminants.

Fluorine Compounds- Fumes and gases from fluorine compounds can be dangerous to health, and can bum the eyes and skin on contact. Local mechanical ventilation or respiratory protection must be provided when welding, brazing, cutting, or soldering in confined spaces involving fluxes, coatings, or other material containing fluorine compounds.

When such processes are employed in open spaces, the need for local exhaust ventilation or respiratory protection will depend upon the circumstances. Such protection is not necessary when air samples taken in breathing zones indicate that all fluorides are within allowable limits. However, local exhaust ventilation is always desirable for fixed-location production welding and for all production welding of stainless steels when filler metals or fluxes containing fluorides are used.

Fumes Containing Zinc- Compounds may produce symptoms of nausea, dizziness, or fever (sometimes called “metal fume fever”). Welding or cutting where zinc may be present in consumables, base metals, or coatings should be done as described for fluorine compounds.

Measurement of Exposure

The American Conference of Governmental Industrial Hygienists (ACGIH) and the U.S. Department of Labor, Occupational Health and Safety Administration (OSHA) have established allowable limits of airborne contaminants. They are called threshold limit values (TLVs), or permissible exposure limits (PELS).

The TLV (a registered trade mark of the ACGIH) is the concentration of an airborne substance to which most workers may be repeatedly exposed, day after day, without adverse effect. In adapting these to the working environment, a TLV-TWA (Threshold Limit Value-Time Weighted Average) quantity is defined. TLV-TWA is the time weighted average concentration for a normal 8-hour workday or 40-hour workweek to which nearly all workers may be repeatedly exposed without adverse effect. TLV-TWA values should be used as guides in the control of health hazards, and  should not be interpreted as sharp lines between safe and dangerous concentrations.

TLVs are revised annually as necessary. They may or may not correspond to OSHA permissible exposure limits (PEL) for the same materials. In many cases, current ACGIH values for welding materials are more stringent than OSHA levels.

The only way to assure that airborne contaminant levels are within the allowable limits is to take air samples at the breathing zones of the personnel involved. An operator’s actual on-the-job exposure to welding fume should be measured following the guidelines provided in ANSVAWS Fl.l, Method for Sampling Airborne Particulates Generated by Welding and Allied Processes. This document describes how to obtain an accurate breathing zone sample of welding fume for a particular welding operation. Both the amount of the fume and the composition of the fume can be determined in a single test using this method. Multiple samples are recommended for increased accuracy. When a helmet is worn, the sample should be collected inside the helmet in the welder’s breathing zone.

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