What is HEPA filter?

  • 12, 10, 2021

what is HEPA filter

HEPA filter is becoming more and more popular in contamination control. It is applied in many industries such as electronics, pharmaceutical industries, and even home appliances. What is HEPA filter, how many types of HEPA and how does it work? Let's find out in this article.

1. What is HEPA filter?

HEPA filter or High-Efficiency Particulate Air filter is a kind of filter that can theoretically remove 99.95% of dust, pollen, mold, bacteria, and any airborne particles sized 0.3 microns or larger (µm).

HEPA filter was first designed in the 1940s and used in Manhattan Project to capture airborne radioactive contaminants. A decade later, HEPA filters were introduced commercially. From then on, HEPA filter has gained more and more popularity in industries and in household appliances. 

HEPA filter

2. How many types of HEPA filter? 

According to European standards, there are 17 classes of filters. The higher the class, the greater the efficiency. Classes E10 to E12 are Efficient Particulate Air filters (EPA), H13 and H14 are High-Efficiency Particulate Air filters (HEPA), and U15 to U17 are Ultra Low Penetration Air filters (ULPA). These classes are covered by the European standard EN 1822, which assesses the filtration performance of the filter for the MPPS (Most penetrating particle size).

According to this standard, there are 2 types of HEPA filters: HEPA filter H13 and HEPA filter H14. 

HEPA filter specification

Image: HEPA filter specification

HEPA filter H13 has a filtration efficiency of up to 99.95%, while HEPA filter H14 could filter 99.995% particles.

3. How a HEPA filter works? 

Most HEPA filters are composed of interlaced fiberglass fiber that is twisted and turned in countless directions to create a fibrous maze. 

For particles greater than 0.3 μm in size, they can’t get through. Large particles move in a straight path, collide with the filter fiber due to inertia. 

For smaller particles, they could go through the hole, but they collide with one another and move randomly. As a result, they hit and stick to the filter fibers. This is what’s called the Brownian movement. 

Read more: Clean room filter: Amazing things you don't know about

4. HEPA filter applications 

HEPA filters are used in a wide variety of applications such as electronics, aerospace, computer, nuclear power, pharmaceutical industries. Hospitals,  laboratories and even homes are also in need of high-efficiency air filters. 

HEPA filter in cleanroom 

HEPA filters are widely used in cleanrooms, lab and factory settings because they create clean and filtered air - the key protection to products and personnel in cleanrooms, etc. 
These filters can be found in cleanroom equipment like fan filter unit (FFU), HEPA box, dynamic pass box, air shower, blower filter unit (BFU), dispensing booth, biosafety cabinets, etc. 

HEPA filter in household appliances

Air pollution has caused many health problems. In this case, the HEPA filter might capture a range of allergens, dust, and mold. 
Therefore, manufacturers of consumer products also add HEPA filters to home appliances: the HVAC system, portable air purifiers, and vacuum cleaners.

5. When to replace HEPA filter? 

HEPA filters have a certain life span, whether they are used in fan filter units or at any other place. It has exceeded the initial pressure drop rate of 100Pa, or equal to 2 times higher than operating initial pressure drop (3 times higher for low resistance and sub-high efficiency) in more than 1 year. The HEPA filter should be replaced if it exceeds the standard.

Read more: Pressure drop in air filtration 

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