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More About HVAC Bag Filters
Bag filters are designed to deliver high performance with minimal running costs. Every bag filter in the range offers high surface area, which allows greater dust holding capacity without restricting airflow. This, combined with a low pressure drop and long service life, means less frequent filter replacements, reduces labour costs and lower total cost of ownership (TCO).
Coarse grade bag filters use high-lofted synthetic non-woven media, a thick, fluffy, low-density material. This increases the available surface area and boosts dust holding capacity while keeping resistance low. As a result, these filters maintain airflow for longer and are ideal for pre-filtration or low to medium final filtration. The depth of the media allows large volumes of air to pass through while capturing a high volume of particulate, extending service life and improving system efficiency.
Fine grade bag filters are available in grades M5, M6, F7, F8 and F9. Their denser media structure makes them suitable for medium to fine final filtration or as pre-filters for higher grade systems such as HEPA installations. They provide stable, reliable performance in environments where finer particulate control is required.
F7 bag filters are the most commonly used grade across the UK. They offer an excellent balance of fine dust capture and low pressure drop. F7 filters are widely used as the standard for modern ventilation requirements and are frequently used as pre-filtration for HEPA systems.
Common questions about Bag Filters
What are bag filters used for?
Bag filters are used in HVAC systems to remove dust and airborne particles while keeping airflow stable. The multi‑pocket design creates a large surface area, giving the filter a high dust holding capacity while maintaining a low pressure drop. This also results in a long service life, meaning fewer filter changes, reduced labour costs and a lower total cost of ownership (TCO).
Learn more by reading our article "What are Bag Filters in HVAC?"
How often should bag filters be changed?
The frequency of bag filter replacement depends on factors like the amount of dust in the air, the size of the particulates, whether the system uses a pre‑filter and the air velocity moving through the filter. As a general guide, bag filters are typically changed every 6 to 12 months. Once resistance rises beyond the recommended level or the media is visibly loaded, performance and efficiency will start to decline.
What are the different types of bag filters?
There are generally three types of bag filters used in HVAC systems: Coarse Grade bag filters, Fine Grade bag filters and Rigid Bag filters.
Coarse Grade bag filters typically include G4 and Activated Carbon variants. These use high‑lofted synthetic media, which is thick and fluffy, giving them a large surface area and high dust holding capacity.
Fine Grade bag filters cover the M5, M6, F7, F8 and F9 efficiency classes. These are designed for medium to fine final filtration or as pre‑filters for higher‑grade systems such as HEPA filters. Within this group, F7 is the most commonly used grade due to its strong balance of low pressure drop and filtration efficiency.
Rigid Bag filters are built with a solid plastic frame instead of a soft pocket design. The filters offer high dust holding capacity, low pressure drop and energy efficiency and the compact design allows the filter to replace standard synthetic bag filters or panel filters. They offer similar efficiency classes to Fine Grade bags but with a more robust, rigid construction.
Can bag filters be cleaned?
No, bag filters can’t be cleaned or washed. They’re designed to be replaced, not reused, because cleaning damages the fibres and destroys the filter’s efficiency. Bag filters have a long service life, due to their large surface area and high dust holding capacity, so replacement is infrequent.