Exposures at the Welding Shop
Do you work at a welding shop? Or are you the manager looking after a crew of journeyman welders? Then you’ve probably wondered about the clouds of smoke produced during welding activities that seem to linger in the shop and build over the shift. So, should you be concerned?
Like most gray-area questions, being concerned about welding smoke at your shop depends on many factors. What you’ll need to take into consideration includes:
- the number of welders working on a given shift;
- the size of the facility, including the height of the ceilings, or if the work is completed outdoors or in a make-shift hoarding-type shelter;
- the workload and duration of welding completed during a typical shift;
- the types of welding being completed (ex: MIG);
- the types of metal substrate, such as mild steel, stainless, nickel alloys or custom high manganese products;
- the consumables used and their composition;
- the presence of surface coatings, corrosion inhibitors or other contaminants on the metal, such as hydrocarbons or sludge; and,
- the presence of ventilation, such as local exhaust ventilation or general dilution ventilation.
Must-Do’s and Should-Do’s
A proactive, modern employer should endeavour to protect workers from undesirable exposures, and to keep concentrations of harmful contaminants as low as reasonably achievable. Having said that, regulations are in place to specifically mandate the allowable concentrations to which workers may be exposed without anticipating adverse health effects. The regulations will vary from area to area so be sure to check the specifics for your region. For instance, the U.S.-based Occupational Safety and Health administration mandates a permissible exposure limit (PEL) of 10 mg/m3 for general industry; however, the American Conference of Governmental Industrial Hygienists (ACGIH), the agency who’s work informs numerous jurisdictions globally, specifies a threshold limit value – time weighted average (TLV-TWA) value of 5 mg/m3.
Employers are typically required to evaluate the potential for worker overexposure to airborne contaminants, which often necessitates air sampling. Once air sample results are in hand, the results can be compared to applicable regulated exposure limits.
Employers are typically also required to evaluate the performance of local exhaust ventilation (LEV) equipment, if in place. In short, the equipment must be operating as designed by the manufactured, and must be used appropriately by the workers. Oftentimes the equipment will be bought, but will collect dust when workers place it off to the side due to the inconvenience of continually repositioning the equipment as they work.
If air sample results indicate the potential for overexposures to certain substances, controls must be implemented. More often than not, the mechanism of control will fall back to respirators. If employers rely on respirators to keep their workers safe, most jurisdictions will also stipulate requirements for training workers in the use of the respirators, ensuring workers are fit tested for their masks, and oftentimes that a respiratory code of practice is in place for the worksite.
So where should one start in order to determine where to focus your efforts in evaluating the safety of the work site? The individual should review the MSDS for the welding rods, shield gases, surface coatings and information pertaining to the composition of the metal substrate. The specifics for these products will guide the likely exposures. Given the materials being modified (i.e. steel and steel composites), the most common exposure hazard is iron oxide. Stainless steel may impose a hexavalent chromium exposure hazard, and products such as high manganese steels may pose a manganese exposure hazard.
As most shield gases are relatively inert, and are typically combinations of carbon dioxide, nitrogen, helium, argon or other noble gases, the main hazard is the potential for oxygen displacement, and the creation of an oxygen deficient atmosphere. If a gas cylinder is well maintained and used as directed, it’s unlikely that an oxygen-deficient environment will occur. A hazard may be presented if fluorine is present which may react with other compounds and form fluorides.
Sampling and Analysis
The majority of metals and metal oxides can be collected and analyzed on a single type of air sampling media (mixed cellulose ester cassettes). In other words, individual samples for each type of metal or metal oxide are not required. Individual samples should be collected on a selection of workers. Similarly, many analytical laboratories will offer a package tailored to welding samples, so that the assessor can submit the samples and have each analyzed for a wide number of metals.
If the desire is to check for potential overexposures to specific compounds, such as fluorides, isocyanates or aldehydes, the standardized sampling methodology and analytical laboratories should be consulted to confirm sampling requirements.
Measurement of many gases can be done on-site with direct-read instrumentation. The monitors are typically outfitted with sensors specific to a certain gas, such as oxygen, which is then measured at regular intervals. The changes to the concentration of the parameter can be reviewed at the end of the monitoring period.
So if you know that you have overexposures occurring, or simply want to skip to the end of the line and implement controls, what options do you have?
The following are a list of common controls used:
- respirators, such as half-masks with P100 particulate filters;
- respirator-welding helmet combination products that serve to protect the worker from both welding fumes and arc flash simultaneously. These products are typically reported as being more comfortable by the wearer;
- local exhaust ventilation, which necessitates the worker to buy in to using the equipment;
- moving welding activities from confined areas to more open spaces or completely outdoors;
- substituting the metals and consumables in use for those with lower concentrations of harmful contaminants; and,
- increasing the volume and rate of general dilution ventilation in the work area.
So what hazards have you run into at your weld shop? What concerns do workers typically report? Let us know in the comments!