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Air filters are used to remove suspended particles from the air, and their main applications are in HVAC systems and automobiles.
Air filters used in the HVAC industry are classified into four categories based on their efficiency levels:
Low-efficiency filters
These filters can capture particles up to 50 microns. Their materials may include fiberglass, glass wool, or sticky substances known as tackifiers. Their main drawback is that, over time, their components separate from the filter base, causing a significant decrease in efficiency. These filters are mostly used as pre-filters.
Medium-efficiency filters
These filters can trap particles from 5 to 10 microns, and they are usually made of polyester or cotton–polyester fibers. They are often pleated, which increases the surface area for particle separation, although this design also increases airflow resistance and pressure drop. Based on the Arrestance Test, their maximum efficiency is 30%.
High-efficiency filters
High-efficiency filters can capture particles down to 0.3 microns, and their efficiency ranges from 30% to 98% according to the Arrestance Test. Bag filters, rigid filters, and ring panel filters fall into this category.
Very high-efficiency filters
These filters are used for special applications such as hospital operating rooms, laboratories, and industrial cleanrooms. They can capture particles down to 0.12 microns. HEPA filters and ULPA filters are included in this category, and their efficiency can reach up to 99.9999%.
Automobiles
An image of a dirty automotive air filter.
The air filter is an essential component in vehicles. Due to its ability to capture airborne particles, it prevents dust and contaminants from entering the engine. Automotive air filters come in various types. They are typically made of paper and metal, or paper and PU materials. In some filters, felt is used instead of paper. These filters can separate particles as small as 20 microns from the air.
