Blue Sky Filter is a professional air filter supplier and car air filter manufacturer in China since 2009.

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The role of hepa filter

by:Blue Sky Filter     2022-03-09

HEPA filters can remove at least 97.00% of airborne particles 0.3 micrometer (μm) diameter. Particles of this size are difficult to filter and thus are considered the most permeable particle size (MPPS). Are larger particles or smaller filtered with high efficiency.

HEPA filters consist of randomly arranged fibre mats. The key metrics that affect the effect are fiber density and diameter and filter thickness. The airspace between the HEPA filter fibers is greater than 0.3 μm. The common assumption that a HEPA filter acts like a sieve where particles smaller than the largest opening may pass through is incorrect. As for membrane filters the particles are so large that they are as wide as the opening or distance between the fibers cannot pass between them at all. But HEPA filters are designed to target smaller pollutants, and particles are primarily trapped (they stick to fibers) by one of three mechanisms:

Intercept particles that engage in streamlines in air streams coming on fibers A place within a radius and obeying it. Packing larger particles cannot avoid fibers by following the curved contours of the air stream and are forced to bury directly in one of them; this increases with reduced fiber separation and higher air velocities. An improved mechanism of diffusion is the result of collisions with gas molecules consisting of small particles, especially those below 0.1 μm in diameter, thus being hindered in their path and delayed across the filter; this behavior is similar to that of Scotland The action of botanist Robert Brown also raises the possibility that the particle will pass above one of two mechanisms; it becomes dominant at lower air velocities. Diffusion predominates below the 0.1 μm diameter particle size. Tightening and interception predominate above 0.4 μm. In between, around the 0.3 μm MPPS, diffusion and interception dominate.

Filter airflow resistance and final filter airflow resistance are typically measured as pressure drops across the filter.


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