What is a HEPA filter？

A high-efficiency filter is a device used for air filtration, mainly for removing small particles, microorganisms, and other impurities from the air to meet the strict requirements of specific environments for air quality.

Structural composition

Filter material: The core component of an efficient filter is the filter material. Common filtering materials include glass fiber filter paper, polypropylene fiber filter paper, etc. These filters have an extremely fine fiber structure that can effectively intercept tiny particles. Taking glass fiber filter paper as an example, its fiber diameter can reach the micrometer or even nanometer level, and it can capture particles in the air through physical adsorption and interception.

Outer frame: The filter material is fixed in the outer frame, usually made of metal (such as aluminum alloy) or plastic (such as polystyrene). Metal frames have high strength and stability, making them suitable for environments that require high structural strength for filters, such as high air volume ventilation systems; Plastic frames are relatively lightweight and cost-effective, typically used in situations where weight and cost are more sensitive.

Sealing material: In order to ensure that air does not leak from the edge of the filter during the filtration process, HEPA filters are also equipped with sealing materials. A common sealing material is rubber (such as chloroprene rubber), which can be tightly installed on the installation frame of the filter to ensure that all air can be filtered through the filter material.

Filtering principle

Interception: When air flows through a HEPA filter, particles in the air are intercepted when they collide with the filter fibers. For larger particles, this interception effect is more pronounced. For example, particles with a diameter larger than the spacing between the fibers of the filter material will be directly blocked by the fibers and unable to pass through the filter.

Inertial collision: If particles in the air have a certain velocity and mass, when they change direction with the airflow, they will collide with the filter fibers and be captured due to the influence of inertia. This principle applies to smaller particles with relatively high velocities.

Diffusion: For very small particles (such as those smaller than 0.1 μ m in size), they will exhibit irregular Brownian motion in air. During this movement, particles have the opportunity to come into contact with the filter fibers and be adsorbed. This diffusion is one of the important mechanisms for HEPA filters to capture small particles.

Performance parameter

Filtering efficiency: This is one of the most important indicators for measuring high-efficiency filters. It represents the proportion of particles of a specific size that the filter can effectively filter out. For example, for particles with a diameter of 0.3 μ m, the filtration efficiency of HEPA filters can usually reach over 99.97%. Different application scenarios have different requirements for filtration efficiency. In environments with high cleanliness requirements such as clean rooms, filters with higher filtration efficiency are needed.

Resistance: Air will experience a certain resistance when passing through a HEPA filter. The magnitude of resistance is related to the type, thickness, and filtration speed of the filtering material. Generally speaking, the higher the filtration efficiency, the thicker the filter material, the faster the filtration speed, and the greater the resistance of the filter. In practical applications, it is necessary to minimize the resistance of the filter while ensuring filtration efficiency, thereby reducing the energy consumption of the ventilation system.

Dust capacity: Dust capacity refers to the amount of dust that a filter can hold before reaching the specified resistance or the filtration efficiency drops to a certain extent. The larger the amount of dust, the longer the service life of the filter. Different filtering materials and structures have varying dust removal capabilities. For example, some high-efficiency filters with thick filters have relatively large dust capacity, but correspondingly, their resistance may also be higher.

Suzhou Pharma Machinery Co.,Ltd.

2025/04/25

Alice