Filters are responsible for removing hazardous airborne particles from contaminated air before it is discharged or recirculated. Without effective filtration, welding fume could remain in the workplace and continue to expose employees. Most welding fume extraction systems use multiple stages of filtration — typically a pre-filter, a main cartridge filter and, where required, a high-efficiency (HEPA) filter — and selecting the correct arrangement helps maintain air quality, improve extraction performance and protect both equipment and operators.
Weldability SIF supplies the Fumex range of welding fume extraction equipment under the Extractability brand, and our technical team helps businesses specify filtration that matches their welding process, materials and workplace requirements.
How do welding fume filters work?
Welding fume filters capture microscopic airborne particles as contaminated air passes through the filter media. Cleaned air then exits the extraction system while the captured particles remain held within the filter.
Welding fume consists of extremely small airborne particles, many of which are invisible to the naked eye. Modern extraction filters are designed to capture these fine particles, helping reduce employee exposure and improve workplace air quality. The efficiency of any filter depends on the type of filter, the particle size involved and how well the system is maintained.
What types of filters are used in welding fume extraction?
Many extraction systems use several stages of filtration working together. The correct arrangement depends on the welding process, the materials being welded and the level of filtration required.
What is a pre-filter?
A pre-filter removes larger airborne particles before they reach the main filter. This helps protect the primary filtration system, extends filter life and reduces overall maintenance costs. Replacing pre-filters when required is one of the most effective ways to keep contaminants out of the main filter and lower running costs.
What is a cartridge filter?
A cartridge filter is a pleated cylindrical filter designed to provide a large filtration surface within a compact space. Cartridge filters are widely used in industrial welding fume extraction because they combine high filtration efficiency with long service life and relatively low maintenance.
What is a HEPA filter, and do I need one?
HEPA stands for High Efficiency Particulate Air. HEPA filters are designed to remove extremely small airborne particles with very high efficiency, and are commonly used where very clean discharged air is required or where particularly fine particles are generated.
Whether you need HEPA filtration depends on your welding process, workplace risk assessment and extraction system design. Certain applications may benefit from HEPA filtration, particularly where very fine airborne particles are generated or additional filtration is required. Extractability can advise on the most appropriate filtration system for your application.
What is filter efficiency?
Filter efficiency describes how effectively a filter removes airborne particles from the extracted air. Higher efficiency generally means more hazardous particles are removed, helping improve workplace air quality and maintain extraction performance. Matching efficiency to the application matters: selecting the wrong filter can reduce extraction efficiency, increase maintenance costs and shorten equipment life.
Why do welding filters become blocked?
Filters gradually become loaded with captured welding fume and dust during normal operation. As contamination increases, airflow may reduce unless filters are cleaned or replaced in accordance with the manufacturer’s recommendations. Routine maintenance helps maintain extraction efficiency.
Blocked filters do more than reduce airflow. They increase system resistance, causing the fan to work harder to maintain airflow — which raises energy consumption and places unnecessary strain on equipment. An extraction system that is not maintained may also no longer provide effective control of welding fume, which can affect HSE compliance. Regular filter maintenance therefore protects performance, running costs and your duty to control exposure under UK guidance.
How do I know if my filter needs replacing?
Regular inspection is the best way to determine when replacement is required, because filter life varies depending on welding volume, the materials being welded and the amount of airborne contamination generated. Waiting until airflow has significantly reduced can affect extraction performance.
Signs that a filter needs changing include:
- Reduced airflow at the extraction hood
- Poor fume capture, with smoke escaping into the workshop
- Increased fan noise
- Filter condition indicators fitted to the extraction system showing the filter is loaded
Replacing filters before they become excessively blocked helps maintain effective LEV performance. If you are seeing these symptoms, our LEV testing and compliance guide explains how a Thorough Examination and Test confirms the system is still controlling fume effectively.
Can welding filters be cleaned, or should they be replaced?
Some industrial cartridge filters are designed to be cleaned using automatic or manual cleaning systems, while others are intended to be replaced. Always follow the manufacturer’s maintenance recommendations to avoid damaging the filter media.
Automatic filter cleaning uses pulses of compressed air, or other cleaning methods, to remove accumulated dust from the filter surface during operation. This helps maintain airflow, extend filter life and reduce routine maintenance.
Manual filter cleaning requires the operator to clean or replace filters during scheduled maintenance. Regular inspections help ensure filters continue operating efficiently and prevent unnecessary reductions in airflow.
How can I extend the life of my filters?
Correct hood positioning, regular maintenance, routine inspections and replacing pre-filters when required all help maximise filter life. Keeping contaminants out of the main filter reduces operating costs and improves extraction performance. If filters are blocking quickly, the cause is often heavy production, unsuitable filters, poor pre-filtration or incorrect system design — reviewing the application and maintenance schedule usually identifies opportunities to improve filter life. Our guide to choosing a system covers how to match the equipment to your workload from the outset.
How should used welding filters be disposed of?
Used filters should be disposed of in accordance with the manufacturer’s recommendations and your workplace waste management procedures. The method of disposal may depend on the materials captured during the welding process, as some welding fume contains substances that require specific handling.
Recirculation vs exhaust to atmosphere
Where cleaned air is recirculated back into the workshop rather than exhausted to atmosphere, filtration becomes even more important, because any particles not captured by the filter are returned to the breathing zone. This is one reason high-efficiency or HEPA filtration may be specified for recirculating systems, particularly where very fine particles are generated. The right approach depends on your workplace risk assessment, the welding process and how the extraction system is designed.
Matching the filter to the welding application
The appropriate filter always depends on the welding process, production volume and extraction system design:
- MIG welding — a correctly specified filtration system removes welding fume efficiently while maintaining reliable airflow throughout the working day.
- Stainless steel welding — produces particularly fine airborne particles that require effective filtration, selected according to the system design and materials being welded.
- Laser welding — often generates extremely fine process particles that require high-performance filtration suited to the laser process and production environment.
Professional advice ensures the filtration system matches your welding process, airflow requirements and workplace environment. Whether you are specifying a new mobile extraction unit or upgrading an existing installation, Extractability supports customers with filtration solutions designed to improve workplace air quality while helping maintain effective welding fume control.
To explore the wider topic, return to our fume extraction knowledge centre, or contact Weldability SIF for technical advice on filter selection and LEV performance.