The agency’s Hierarchy of Controls provides the steps for employers to take in order to comply with environmental regulations and improve worker safety. Before companies implement controls, it is recommended to conduct air sampling to understand the types and levels of contaminants in the welding environment. Multiple samples may be necessary to properly characterize an employee’s exposure to weld fumes.
Using the Hierarchy of Controls, OSHA recommends minimizing weld fume exposure through these steps:
1. Elimination or Substitution, such as using low-manganese filler metals or changing the shielding gas
2. Engineering Controls, such as fume extraction equipment or centralized ventilation
3. Administrative Controls, such as proper body positioning
4. Personal Protective Equipment (PPE), which includes respiratory protection such as half masks, powered air purifying respirators or supplied air respirators
Note: The examples listed after each of the above steps are not inclusive; there are many other activities associated with each step. Those listed are for the purpose of this article only.
This article will discuss eight key practices to help effectively manage weld fume, particularly from the Engineering Controls and PPE steps identified in OSHA’s Hierarchy of Controls, steps 2 and 4 above. Keep in mind that proper employee training is critical to the successful execution of these controls and other weld fume management activities.
Also note that every welding environment is different and therefore should be evaluated by a qualified industrial hygienist to determine the appropriate course of action for fume controls.
Proper operation of a fume extraction system
Fume extraction systems are part of the second step in OSHA’s Hierarchy of Controls for managing fume, Engineering Controls. There are a few key things to know about these systems to get the best results.
1. Source capture, which captures and removes contaminants at their source before they reach a worker’s breathing zone, is the preferred method of weld fume extraction. Capture devices are available in different shapes and sizes, and are rated based on the amount of cubic feet of air they extract each minute (cubic feet per minute or cfm). The diameter of the ductwork is directly proportional to the cfm of air that the device can move. A low-vacuum/high-volume fume extraction system will feature larger ductwork and move a larger volume of air but at generally lower vacuum pressures. These systems offer larger capture zones. Conversely, high-vacuum/low-volume systems capture weld fume much closer to the weld, via a smaller attachment, such as a nozzle. The smaller ducting helps get into restricted spaces and removes the fume much closer to the weld itself.
To get the very best results, make sure the capture velocity is sufficient to pull the fume away from the operator’s breathing zone. Consult with an industrial hygienist if in doubt of the cfm capacity needed for the application.
Following proper welding procedures and avoiding overwelding (putting down more consumable than is necessary) also helps reduce the amount of fume generated, so there is less that must be removed by the fume extraction system in the first place.
2. Proper positioning of the fume extraction arm is key to the effectiveness of the system. The hood must be positioned properly so it’s pulling the fume away from the worker’s breathing zone. When using a moveable hood or fume extraction arm, position it above the arc and angle at approximately 45 degrees. The hood distance will vary depending on the velocity and volume of air being captured, though in general it’s approximately the distance of 1 1/2 duct diameters away.
3. Limiting cross ventilation and employing proper body positioning can help the fume extraction arm work in the most effective manner, and proper employee training can help minimize exposure to the weld fume path. â€¨â€¨Limiting cross ventilation helps minimize interference with the capture of the fume, lessening the opportunity for the fume to be blown back at the welding operator or at other workers nearby. Welding operators should position themselves so that the airflow is moving from their back to their front. A cross draft can be used advantageously to blow fume away from the operator and toward the hood, but take care to minimize any detrimental cross drafts. Using partitions or curtains in the welding enclosure can help control cross ventilation.
A welding operator should also avoid positioning his or her body between the weld and fume extraction arm, to keep his or her face out of the weld plume and to prevent blocking the suctioning capabilities of the fume extraction arm.
4. Fume extraction system maintenance is an important part of saving time and money, ensuring the system works to its fullest capacity and helping create a safer environment. Systems are available with disposable filters or with self-cleaning feature models. A good fume extraction system that uses disposable filters should have a gauge to indicate the filter condition. A filter that gets too dirty won’t let as much air pass through, which reduces the amount of airflow at the hood for effective fume collection. When using a self-cleaning fume extraction system, make sure the compressed air line is hooked up and working properly, and that the air is clean and dry. There are numerous types of filters available, and choosing the appropriate filter can help optimize fume collection. Again, consult with an industrial hygienist when in doubt of the best filter for the application.
Proper respirator selection and use
5. Choosing the right respirator is critical. OSHA has identified two major types of respirators: air-purifying and atmosphere-supplying. Air-purifying respirators have filters or cartridges and remove contaminants from the air by filtering them prior to reaching the welding operator. Atmosphere-supplying respirators provide clean air from an uncontaminated source. Proper selection depends on the work environment, as well as the actual exposure levels to the regulated metals. Respirators are rated with an assigned protection factor (APF) that denotes the workplace level of protection that a respirator is expected to provide.
Common types of respirators used in welding applications are:
•Dust masks, which are paper-like masks that have an APF of 10.
•Half masks, which can fit under a welding helmet, have replaceable filters or canisters, and have an APF of 10. These require a fit test for mandatory use.
•Powered air purifying respirators (PAPRs) use a belt-mounted blower assembly to distribute filtered air through a breathing tube to the user’s welding helmet and have an APF of 25. These systems have replaceable filters and/or canisters and do not require a fit test when used with a welding helmet assembly.
•Supplied air respirators distribute breathing air through an airline hose to the wearer’s belt-mounted air-control device, which is then sent through a breathing tube to the welding helmet. These systems have an APF of 25 (with a welding helmet) and can also offer heating and cooling options. No fit test is required when used with a welding helmet assembly.
To determine which of these respirators is appropriate, it’s necessary to consider the maximum use concentration (MUC), which is calculated by multiplying the APF of a respirator by OSHA’s permissible exposure limits (PEL) or MUC = APF x OSHA PEL. OSHA considers the MUC to be the upper limit at which the class of respirator is expected to provide protection. Whenever exposures approach the MUC, companies should select the next higher class of respirators to provide necessary protection for employees. It’s also important to select only National Institute for Occupational Safety and Health (NIOSH)-approved respirators.
Because respirators aren’t one-size-fits-all, proper fitting is key as well. When choosing a half mask respirator, specifically, a fit test for mandatory use is required to ensure a proper seal. Fit testing can help identify the make, model, style and size of respirator best suited for each employee and can ensure the respirator provides the level of protection as designed. Fit testing should be administered before the respirator is used and then again annually or whenever there is a change in the user’s physical condition that could affect the fit of the respirator.
6. Having the proper documentation for respirators is a critical part of maintaining OSHA compliance. While a written respiratory protection program is required for both mandatory and voluntary respirator use, the requirements do vary. For mandatory use, the written plan must include respirator selection; a medical evaluation showing that each employee is physically able to wear a respirator; fit testing for tight-fitting respirators; use in routine and emergency situations; established schedules for cleaning, storage and maintenance; procedures to ensure air quality and flow for atmosphere-supplying respirators, employee training; and evaluation of the respiratory program. For voluntary use, the plan requires medical evaluations, and established schedules for cleaning, storage and maintenance.
7. Respirator inspection, prior to usage, is an important step that can help ensure the worker is fully protected. Employees need to be trained on proper inspection procedures prior to using any kind of respirator. It is a good idea to read the respirator’s Users Instructions for inspection procedures. In addition to respirator inspection, employee training should cover the general requirements of OSHA respiratory protection standards, as well as an explanation of why a respirator is necessary. Employees should understand the proper selection of respirators; the consequences of improper fit, usage or maintenance; the proper procedures for maintenance and storage; and how to use the respirator effectively in emergency situations.
8. Proper procedures for respirator maintenance and storage — including for cleaning and replacing the units — are also important. A filter change schedule should be established as part of the written respiratory protection program. If the respirator filter becomes damaged, a welding operator detects breathing resistance, or in some cases, battery life quickly diminishes, it is best to check the respirator’s filter assembly and change filters if needed. One issue to note: Unlike with other fume extraction products, the filters on respirators cannot be cleaned, so they must be replaced.
Maximizing weld fume management solutions
In addition to selecting the most appropriate weld fume management solution for the application and environment, welding operator training is also important to establish and maintain successful weld fume management practices and compliance. It’s critical that employees understand proper fume extraction system and respirator use to maximize the benefits these solutions can provide toward a cleaner and safer work environment.