Electrostatic Air Purifier 101



Electrostatic air purifier is a kind of ionic air purifier. Like other ionic air purifiers, it charges or ionizes air particles. The machine then draw those charged particles into a collection plates which are charged with different polarity from the particles. So, if for instance, the machine charges particles with negative ions, then the collection plates should be charged positively. Because of the opposite polarity, the ionized particles can stick easily to the collection plates of an electrostaic air cleaner. This kind of machine, when used in industry, is also called an electrostatic precipitator because it collects charged particles inside the machine.

The electrostatic air filtration system is pretty efficient in absorbing particles as long as the machine is good enough in charging the particles, can produce a strong charge on the collection plates and has a large total area of the collection plates. This will ensure that most of the incoming particles are charged and there is enough space for all those charged particles to stick to the collection plates. If either one of that three factors are not good enough, the efficiency of the machine will plummet. Also, entering the equation is the optimal use of fan to ensure that air flows fast enough into and out of the air purifiers.

Since an elestrostatic air cleaner theoretically can charge a wide range of particles size-wise, then in a good machine, an electrostatic air purifier can curb particles up to 0.1 micron in size. So in a sense, it can be comparable to a HEPA air purifier, because a True HEPA filter can trap particles optimally up to 0.3 micron and at a reduced efficiency - up to around 0.1 micron.



Types of Electrostatic Air Cleaner.

By Stages

There are several different types of electrostatic air purifiers based on the number of stages it has for cleaning up air:
  • One stage.
    Some electrostatic precipitatorss use a one-stage system to clean the air. In this kind of machine, basically the air purifier charges the outside particles, draws the charged particles in and stick the particles to the plate. Therefore in this method, the particles only undergo one step once inside the air purifier, which is sticking to the collection plate.
  • Two stage
    This type of electrostatic air cleaners first draw the dirty air in, and once the air is inside, the air purifier does two things to them:
    • Charge them using high-voltage wires.
    • Pull the charged particles to the collection plates.
  • Many stage
    Some electrostatic precipitators combine the electrostatic air filtration method with mechanical filtration to increase the efficiency, through the use of a prefilter.

By The Types of Collection Plates

Different electrostatic precipitators use different types of collection plates. They can be divided into three groups:

  • Electrostatic air cleaners with original collection plate.

  • Ionic air cleaners with electrostatic air filter. In essence, this is a charged filter which acts as a collection plate. It's much more efficient to have an electrostatic air filter than just metal collection plates because a charged filter trap particles in two ways:
    • Through the use of charge.
    • Through its property as a filter.
    This way, some particles which manage to get into the air purifier and not charged or weakly charged (usually the small ones) can still be arrested, whereas plate collector will only trap charged particles. One of the premium air purifier manufacturer, Blueair, uses this kind of filter, and therefore their air purifiers manage to achieve high efficiency, have above average air flow and are silent.

  • Electrostatic air purifiers with modified collection plates.

    Honeywell electrostatic air purifier uses IFD (intense field dielectric) plates instead of the oldie goldie metal collection plates since IFD plates have been proven to deliver stronger charge and can afford being dirty without resulting in crackling noise or electrical break. With the ordinary electrostatic precipitator plate, when the plates get dirty, they decrease dramatically in efficiency and produce crackling noise. This is not the case with the IFD plates. Therefore, if you own an electrostatic air purifier with IFD plate, you don't have to wash the plate that often.



The Positive Aspects of Electrostatic Air Purifiers.

  • Silent or not noisy.
    An electrostatic air purifier is definitely more silent than a HEPA air purifier because its fan does not have to work that hard to push the air through a filter. In a HEPA air purifier, the fan has to work at high speed so that the air can flow fast enough through the filter. It is even more pronounced in a HEPA air purifier with a tight housing because the pressure is greater. In contrast, electrostatic air cleaner 'breathe' more easily because there is no filter which acts as a barrier for the air to go through. It allows the fans to work much less harder, and therefore produce much less noise.

  • No filter replacement.
    If you own an electrostatic air cleaner which does not have any media filter to change, then you don't need to change anything. This is one factor where owning an electrostatic air purifier instead of a HEPA air purifier can save you money. Just be prepared, though, that in order to keep your machine in a tip top condition you should provide a sweat equity instead (see below).


Potential Drawbacks of Electrostatic Air Purifiers.

  • A lot of plate washing or wiping.
    Yup, as much as you love the saving-money aspect as a result from owning an electrostatic air cleaner which does not need any filter replacement, you should know that in order to keep your unit works with high efficiency, you need to wash the collection plate regularly. As the collection plate collects dust and its surface covered with particulates, their ability to attract the praticles decreases until the plates are taken out and cleaned. The efficiency can start out high around 80-s and can degrade to as little as 20% if the plates become dirty. Besides, the machine will give out pop and crackling sound when the plates get dirty. Hard scrubbing may even be needed if your collection plate becomes so dirty. If you hate this kind of maintenance, get either a HEPA air purifier or an ionic air purifier which utilizes electrostatic air filter or IFD plates (see above) instead.

  • Ozone emission
    Due to the high voltage required to produce electric field in electrostatic air cleaners, this type of air cleaner produces some amount of ozone. EPA gives a limit of 50 ppb ozone to any electronic device to ensure safety. However, a small number of air purifiers which do not follow this guidelines still manage to find their way to the residential air purifier market. So you need to be careful of those. Fortunately, there are a small number of electrostatic air purifiers which do not emit ozone or emit a background/negligible amount of ozone. Since ozone is a lung and soft tissue irritant, those who suffer from asthma or other lung diseases are better not to touch these machines with a 10-foot pole unless you know for sure that they are ozone-free. Online vendors or the manual can give you information whether a particular product is ozone-free.



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