Identifying risks, understanding regulations, and installing and maintaining equipment keep metal fabrication shop floors safe from dangerous fumes and particulates.
The COVID-19 pandemic continues to bring greater awareness of the air we breathe throughout the world. Manufacturing facilities, businesses, schools, restaurants, and other public gathering places are focusing on air quality and questioning what is in the air that can sicken people.
They also are finding new ways to test, monitor, and improve air quality. The lessons learned can be applied to manage fumes in welding and metal processing facilities. These six guiding principles can help a metal fabricating company create a work environment that is safe for its employees and attractive to a new generation of manufacturing workers.
1. Study Your Processes
During the pandemic, manufacturing companies took a long look at how shop floor employees were positioned and interacted with co-workers. They realized that social distancing was an effective tool in helping to minimize the transmission of the Coronavirus, so they took steps to spread workers out and mandate that meetings took place in open areas with small numbers.
Metal processing operations have to do the same when looking to improve indoor air quality. Shop floor operations in many of these facilities generate potentially dangerous fumes and particulates as a part of their everyday routine. These processes include manual and robotic welding (involving gas metal, gas tungsten, shielded metal, and flux-cored arc welding processes), arc gouging, plasma cutting, and laser cutting. The process fumes reduce indoor air quality, endanger workers, and cause electrical component failures.
Fumes consist of tiny airborne dust particles that contain ingredients that can irritate eyes and skin and be toxic when swallowed or inhaled. Common metal processing fumes contain lead oxide, iron oxide, nickel, manganese, copper, chromium, cadmium, and zinc oxide. Welding processes also can produce toxic gases like nitrogen dioxide, carbon monoxide, and ozone.
In addition to affecting air quality, some metal dusts are combustible and increase the chance of a fire or explosion. Because dust collection systems can be a main source of a fire or explosion, they must be sized correctly and have the proper filters and protection devices to diminish the risk.
2. Identify Airborne Risks
Knowing where to focus is the first step. Determining what specifically should be addressed is the next important move. During the pandemic, once research revealed that the Coronavirus was more likely to be transmitted via the air, efforts focused on masks and social distancing to minimize its spread. In a manufacturing environment, organizational leaders need to know what they are battling on the shop floor.
To identify airborne dust risks, hire an environmental engineering company to perform on-site air sampling along with monitoring to create an air sample analysis. Typically, the result is a report identifying various possible contaminants, documenting permissible exposure limits (PELs), and listing the values found in your facility. This allows you to understand your dust and plan corrective measures to promote safer air quality.
In addition, to comply with the Occupational Safety and Health Administration (OSHA), you need to perform an explosion severity test. This will certify whether or not your dust is explosive. If your dust is explosive, National Fire Protection Association (NFPA) standards 652, 654, and 484 will require a combustible dust hazard analysis to assess risk and determine the necessary fire and explosion protections. Combustible dust testing is different from characteristics testing and should be performed by an accredited lab with the proper equipment per NFPA requirements.
Dust analysis is another excellent tool to better understand the physical properties of your dust. A lab specializing in dust analysis can identify key properties like particle size and shape, density, moisture level, and abrasiveness. This information helps you make proper choices when sizing and selecting a dust collector.
OSHA maintains a list that identifies hazardous chemicals commonly associated with welding, cutting, and brazing operations, with links to more specific information on sampling and analysis, at www.osha.gov/welding-cutting-brazing/chemicals.
3. Understand Regulations and Guidelines
Guidelines issued by the Centers for Disease Control and Prevention have been important to manufacturers during the pandemic as they greatly influence just how they should approach protection of their essential workers. Workers also recognize that their employers are being responsive to the latest recommendations for protection against the virus.
The same applies when it comes to managing risk associated with indoor air quality. Manufacturers should be aware of what the government expects of them.
Under OSHA’s General Duty Clause, Section 5(a)(1), employers must identify and abate hazards in the workplace. This means employers are required to keep records identifying all the dust generated in their facility. If the dust is flammable or explosive, they must follow NFPA standards to manage the dust properly.
Also, OSHA has set PEL thresholds for airborne particle contaminants generated by welding and metal processing. These PELs are based on an eight-hour time-weighted average (TWA) for hundreds of dusts, including those contained in welding and metal processing fumes, and lists them in annotated PEL tables. When initial air monitoring reveals exposures above the action level, facility operators need to implement additional requirements per OSHA.
PEL is expressed as a TWA in micrograms per cubic meter of air (μg/m3) or milligrams per cubic meter of air (mg/m3). Examples of OSHA PELs for metal cutting fume/dust include:
- Cadmium fume: 5 μg/m3 (2.5 μg/m3 action level)
- Hexavalent chromium fume: 5 μg/m3 (2.5 μg/m3 action level)
- Zinc oxide fume: 5 mg/m3
- Iron oxide fume: 10 mg/m3
- Manganese fume: 5 mg/m3
4. Know Particulate by Size
As scientists learn more about the Coronavirus, they are able to offer insight into the virus’s ability to mutate. Keeping tabs on the variants helps society maintain vigilance against an ever-changing enemy.
In the world of manufacturing, air pollutants come in various shapes and sizes. Understanding the risks associated with specific pollutants can help you shape a proper risk management strategy.
The World Health Organization has studied air pollution around the world and developed guidelines based on particulate matter (PM) size. It created categories PM2.5 and PM10 (stated number is particle micron size or smaller). Other recognized sizes are inhalable PM1 and coarse dust (10 microns or larger). In fact, PM Air Quality Standards fall into one of six air pollutant criteria regulated by National Ambient Air Quality Standards under the Environmental Protection Agency’s (EPA) Clean Air Act.
Smaller particles with a diameter of 10 microns or less (≤ PM10) can reach the respiratory ducts, while particles 2.5 microns or less (≤ PM2.5) can lodge deep inside the lungs. Inhalable particles with a diameter of 1.0 micron or less (≤ PM1) can cause much more damage because they can penetrate the lung barrier and enter the blood system.
Regular exposure to PM contributes to the risk of developing respiratory diseases and even lung cancer. Many of the particles produced by welding reside within this range, and the nature and severity of the hazard will vary with the type of material being processed. Whether you are working with stainless steel, mild steel, aluminum, galvanized, or another material, the material safety data sheet is a good starting point for identifying health risks.
5. Manage Regular Maintenance
People were looking for N-95 respirator masks early in the pandemic because they were viewed as the best protection from the airborne Coronavirus. If they were good enough for the medical professionals on the front line, they would work well for everyone else.
With that in mind, the best way to reduce worker exposure to hazardous metalworking fumes is to install dust collection systems with high-efficiency primary cartridge-style filters and secondary safety filters. Primary filter media should be selected for each application based on the dust particle size, flow characteristics, quantity, and distribution. A secondary safety monitoring filter, such as a HEPA filter, increases particle efficiency to 0.3 micron or larger (capturing a high percentage of PM1) and prevents hazardous fumes from discharging into the air if the primary filter malfunctions.
To ensure effective air filtration performance, you must maintain dust collection systems properly. When evaluating the performance of a dust collection system, be sure to consider the entire assembly, not just the collector itself. Important components to check regularly include filter cartridges, intake systems and hoods, ductwork, explosion protection systems, fans, hoppers, pulsing controls, and the compressed air system.
6. Select Proper Filtration
Just as not all masks provide the same level of protection from airborne viruses, not all dust collecting systems work for all industrial applications. One of the key factors to keeping a dust collector operating efficiently over its lifetime is selecting the right filter cartridges based on the specific application and type of dust being collected. The proper filter cartridges also ensure a safe work environment by minimizing worker exposure to hazardous airborne particles and serious combustible dust incidents.
Two basic factors need to be considered when specifying dust collector filter cartridges: media type and fabrication technology. Filter media is the material used in the cartridge to capture dust particles. Generally, each cartridge contains hundreds of square feet of media folded up like an accordion, so it fits in a small space. The base media is usually either a nonwoven cellulosic blend called cellulose or a synthetic polyester or polyester silicone blend called spunbond. The base fabric can be coated with chemicals to provide specific performance properties such as antistick, conduction, static dissipation, and flame retardance.
Fabrication technology is the way in which the media is folded into the cartridge. This is important because it impacts the performance of the collector and how long the cartridges last before they have to be changed out for new ones. For example, when the pleats are uniform across the entire media and held open with a plastic bead between the folds, more fabric is exposed to the airstream and available to capture dust particles.
Industrial dust collectors have pulse cleaning systems that regularly blast dust off the filters, but eventually the dust becomes too embedded to be removed by pulse cleaning. A simple but important safety rule is to change out dust collector filters before they become too laden with dust to maximize the efficiency of the collector and minimize worker exposure. Replace the filter if you notice airflow through the system has reached the differential pressure limit prescribed by the manufacturer, pressure drop across the collector is preventing the system from effectively capturing dust, or if dust escapes the filter into the facility.
The Goal: Protecting Employees
As we wrap our heads around the COVID-19 pandemic, we are reminded that invisible airborne particles can cause great harm and even death to people. Welding and metal processing fumes pose an ongoing health threat that must be managed to maintain optimum indoor air quality. By understanding and following these lessons, manufacturers can protect workers and safeguard the facility from dangerous dust and fumes.
Written by: Jon Ladwig, Metal Industry Specialist, for The Fabricator.