Which is better ? HEPA or Electrostatic ioniser filter ? Part 1

HEPA filter has been used in the world for several decades and still the standard filter for medical center and high-tech chip manufactory. Since a couple years ago, due to the market demand of home use air purifier, another type of filter Electrostatic, based on same mechanism as Ionisator were introduced into home market. 

The main argument of Electrostatic filter is that you don’t need to replace filter so it saves you money. Is that so ? On internet you can find many discussion about HEPA filter and electrostatic filter but many wrong information have been confusing consumers. mechaniek als het ionisch luchtfilter. Het belangrijkste argument voor het elektrostatisch filter is dat je het filter nooit hoeft te vervangen, zodat het je geld bespaart. Is dat ook zo? Op internet vind je vele discussies over HEPA-filter en elektrostatisch filter, maar door veel onjuiste informatie wordt de gebruiker in de war gebracht.

Let’s take a look at HEPA filter. 

The mechanism of HEPA filter is baed on Brownian motion and Van der Waals force .

According to European standard EN 1882, HEPA filter has defined into class H10 – 14. The size of PM 0.3 has been used to define this HEPA class. For general home device, H11 and H12 are common used. More info can be found here

But, is it always better to choose the highest class as possible?

Well, first of all, you need to know that the higher the class is, the larger the wind resistance will occur, so less air flow volume.

According to the suggestion of ANSI/AHAM AC-1  , an air purifier should be able to circulate the air in your room 3-5 times per hour. That mean that even with H11 filter it can already circulate your air 2 times per hour., which mean the filtration rate of PM0.3 has already reached 99.975%.

The graph below is the Filter Efficiency v.s. Particle Size. You can see that the most difficult particle to be filtered is the size between PM0.1 – PM0.3. The size bigger than PM0.3 will be affected by Brownian motion and Van der Waals force. The bigger the size is, the higher the efficiency is. The size of PM1.0 is even almost 99.99%.

So, the fact is that for efficiency of filtering PM2.5, H11 and H13 are almost the same. Therefore, it is not necessary to chase very high class H13 or H14 for instance. It may even lose the advantage of device size, more air flow and less noise.

Read on – part 2>

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