Air filters for industry are divided into 3 phases, namely pre-filter, medium filter, and HEPA filter. Where they are three types of air filters that are often used in air filtration systems to clean the air from various particles and contaminants. Each of these filters has certain roles and characteristics in the filtration process. The following is a brief explanation of the three types of filters:

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1. Pre-filter: Pre-filter is the first step of filter in the air filtration system. Its function is to catch large particles such as dust, pollen, hair and other impurities in the air. The pre-filter is designed with a larger pore size than a medium filter or HEPA filter, so it can capture coarse particles without creating a large obstacle to airflow. The pre-filter helps protect the filter medium and HEPA filter from large particles, thereby extending the life of more expensive and more efficient filters.

2. Medium Filter: Filter medium is the second type of filter in air filtration systems, which usually follows a pre-filter. The medium filter has a smaller pore size than the pre-filter, so it can capture finer particles, including fine dust, smoke and bacteria. This filter helps clean the air further before it passes through the HEPA filter. The medium filter is usually between the pre-filter and the HEPA filter in the air filtration path.

3. HEPA filter (High-Efficiency Particulate Air): HEPA filter is a type of air filter that is very efficient and is able to capture very small particles, even as small as 0.3 micrometers with an efficiency of more than 99.97%. HEPA filters are used to remove very fine particles such as ultra-fine dust, pollen, mold spores, viruses and various other allergens. HEPA filters are widely used in applications where excellent air quality is required, such as in hospitals, laboratories, food manufacturing and aircraft cabins.

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These three types of filters are often used sequentially in air filtration systems to achieve efficient and thorough filtration. The pre-filter helps protect valuable filters such as the medium filter and HEPA filter from large particles, while the medium filter further cleans the air before it reaches the HEPA filter which is very efficient at capturing small particles. The combination of these three types of filters helps improve indoor air quality and protects occupants' health from exposure to harmful airborne contaminants.