Dust Capacity and Performance of Air Filters
The initial dust-handling performance of an air filter is directly related to its service life. The initial efficiency of an air filter, along with the subsequent resistance that builds up as the filter accumulates dust during operation, are key factors: the filter is typically considered to have reached its end-of-service life when its operating resistance exceeds multiple times the initial resistance, or when its efficiency drops to below 85% of the initial efficiency.
The maximum amount of dust a filter can hold before reaching these thresholds—based on standard dust specifications—is called its dust capacity. For ultra-fine glass fiber HEPA filters, the dust capacity is generally around 40 to 500 grams when the air volume is 1000 m³/h.
When filters of the same type have different dimensions, their dust-holding capacities also vary. While it is difficult to calculate the exact relationship between dust capacity and increased resistance, it is generally accepted that the increase in dust capacity and the increase in filtration resistance have a linear correlation. Additionally, if a pre-filter is installed on the air inlet side, the filtration efficiency of the entire system is significantly improved.
Operational experience in nuclear power plants shows that the main cause of high-efficiency particulate air (HEPA) filter failures is excessive dust penetration due to the failure of primary (pre-)filters. When a primary filter is damaged, it can no longer trap dust effectively; a large amount of dust then reaches the HEPA filter, causing the HEPA filter’s resistance to reach critical levels in a short period of time—even leading to filter damage. Therefore, in practical operation, to reduce the frequency of HEPA filter replacements, special attention should be paid to the dust-holding capacity of primary filters.
Primary air filters (often referred to as “initial-effect filters”) work to meet clean air standards. Generally, ventilation filters are designed to capture and adsorb dust particles of different sizes in the air, thereby improving air quality. In addition to dust adsorption, chemical filters can also absorb odors, and are commonly used in biopharmaceuticals, hospitals, airport terminals, residential environments, and other settings.
Ventilation filters have a wide range of applications, including the microelectronics industry, coating industry, food and beverage industry, and more. It is also said that filters are merely a means to achieve the goal of air cleanliness.
