Clearing The Air: Importance Of Filter Replacement For Welding Fume Extraction Systems

The purpose of a filter in a welding fume extraction system is to capture and remove airborne particulates from the workplace environment. Mechanical filters incorporate a filtering medium made from microscopic fibers (fiberglass, cellulose, or polyester fibers, etc.) woven in sheets and typically pleated in a “V” pattern. The pleating of the material increases the surface area of the filter providing an increased capture surface. This white paper discusses several important factors about filter replacement for a welding fume extraction system.


There are three basic types of filters used in welding fume extraction systems. Each performs a specific function:

Pre-filter. The purpose of a pre-filter is to capture larger particulates and remove them from the system so they do not reach the main filter. The pre-filter is typically made from aluminum or steel mesh, and may also act as a spark arrestor.


Main filter. The main filter is designed to capture the majority of the particulates generated from welding and its allied processes. Mechanical filtration can also be used effectively for the grinding process.


After filter. The purpose of the after filter is to filter out any remaining small particulates (approximately 0.1 to 0.3 microns). This is similar to the High-Efficiency Particulate Air (HEPA) filter on a vacuum cleaner.

Lincoln Electric weld fume control products utilize one or more of these filter types, depending on the model.


Overtime, a filter may become saturated with particulate matter. Once this happens, the filter needs to be replaced. Certain indicators will signal the need for a filter change. Some are specific to your fume extraction system itself. Others are related to the welding materials you are using and/or the ambient conditions in the manufacturing environment. Here’s what to look for and be aware of:
  • The need for filter replacement is typically indicated by a gauge, an audible tone, an indicator or a combination of these depending on the features of the system. Always reference the instruction manual to find the indicator mechanism on your extraction unit. You may also notice a decrease in extraction capacity and possibly a reduction in extraction of welding fume if the filter has become oversaturated and is not changed.
  • The rate of welding fume generation may vary based on the welding processes that are used in your operation and the particular welding settings selected. The choice of shielding gases, where applicable, can also influence fume generation. Stick and flux-cored welding tend to generate a higher volume of fume compared to MIG welding and TIG welding, which typically generate less particulate than the other processes. The welding process and settings used may impact the life expectancy of your filter and you should take them into account when you are setting up your replacement schedule.
  • Another factor that will help you anticipate the need to replace your filter includes how many hours and shifts you system is operating. The more hours and shifts worked, the sooner the filter needs replaced.
  • Changes in climate or the environment may warrant a filter check and replacement. When companies do extensive maintenance in the summer months, it’s a good time to schedule a replacement of filters. In the fall and winter months, when windows and doors are closed due to cooler weather, it is a good reminder to make regular checks to ensure that the exhaust systems are functioning properly.


While the importance of replacing filters may seem obvious, it only works if you select the appropriate replacement filter for handling weld fumes.

First, ensure your replacement filters meets welding ventilation requirements established by OSHA and the EPA at the local, state and federal levels.

Second, confirm your replacement filter has the right MERV (Minimal Efficiency Reporting Value). The industrial air filtration industry offers numerous choices of filters – so determining the best option for your welding operation and overall work environment can be challenging.

Fortunately, there is the MERV industry-wide metric for ranking filter performance. The MERV is used to indicate the filter’s particle removal efficiency (PRE) for a specific range of particle size. Rankings are made from MERV 1 to 16; the higher the number, the smaller the particle size and the higher the PRE. The details and method of measuring PRE are provided in ANSI/ASHARE Standard 52.2. Welding typically requires MERV 11, 15 or 16, but welding application and consumable type will dictate what filter MERV rating is required for your system so refer to the ANSI/ASHRAE Standard 52.2 “Understanding MERV” User Guide (November 2014) created by the National Air Filtration Association (NAFA®).


Preventive maintenance is planned maintenance activity designed to ensure consistent and effective operation, improve equipment life and avoid system malfunction. The purpose of any fume control system is to help control worker exposure to welding fume. If not maintained properly, the system may not adequately control that exposure. Preventive maintenance ensures that the equipment is consistently efficient and effective, and that long-term use does not subject the equipment to stresses or potential failures caused by improper care or handling. For instance, if the filter is clogged, the fan motor must operate at a higher level to try to operate effectively. This can result in reduced fume capture efficiency, motor failures or other associated issues.

A successful preventive maintenance strategy includes changing the filter on a regular basis. In addition, equipment operation and cleaning should be scheduled and coordinated to ensure that ducting is clean, fume extraction arms are tuned properly and more. Certain tasks must be scheduled at varying service intervals in order to keep the fume extraction equipment from experiencing any unexpected breakdowns. Preventive maintenance for industrial equipment is an effective way to maintain and extend weld fume control equipment operation and life.

When establishing a filter replacement and preventive maintenance strategy, keep the following suggestions in mind:

  • Use Lincoln Electric genuine filters rather than a generic replacement filter. Lincoln Electric cannot warrant or ensure proper operation of the unit if a generic filter replacement is used. This can affect the operation of the system.
  • Know the regulations, requirements and restrictions that apply to the filter’s disposal. It may be necessary to have the material tested in order to understand if the waste material is regulated. Environmental regulations regarding waste disposal can vary, depending on federal and local requirements.
  • Make sure to have a consistent schedule for procuring and installing spare parts and conducting regular service.
  • Allow for regular system checks of the cleaning program within the programmable logic controller (PLC) and the differential pressure monitoring system.
  • Ensure that employees are not overexposed to airborne dust and contaminants during filter maintenance activities. Take any proactive measures necessary to protect against overexposures such as using protective equipment, disposable coveralls and/or respiratory protection.


Proper protocol should be followed when disposing of a used filter. Depending on what elements have built up on the filter, you may have to treat it as a hazardous material. It’s important to understand the correct method for disposal as this can have an effect on the overall cost of operation. Answer these questions when determining proper fume exhaust filter disposal for your welding application.
  • What is your company’s or facility’s hazardous waste generator status?
  • Do you have sufficient generator knowledge to “profile” the waste stream?
  • Do you need to perform testing to determine what the hazardous waste codes are?
  • Do you know the federal, state, and local regulations related to disposal?

If your team is not experienced with these issues, contact a qualified local environmental consultant or your state environmental regulatory agency (EPA) for guidance on the requirements of your state’s environmental rules.


In addition to the usual factors that degrade filter effectiveness over time, there are additional factors that can actually shorten filter life:
  • Contaminants can enter the compressed air system, which in turn make their way into the fume control system. Keep your compressed air system as clean, dry and oil-free as possible.
  • Additives to the base metal. Be aware of any oily process or coatings (such as anti-spatter agents, rust preventatives, etc.) that have been applied to the base metal. These have a high probability of vaporizing and entering your fume control system.


Fume control is an integral part of any welding operation, and proper filtering is critical to an effective fume control system. Safe execution of filter replacement and proper fume exhaust system maintenance can help ensure employees are not overexposed to airborne particulates. This will result in a cleaner, safer, more efficient and more productive manufacturing operation.