Should you consider an air ionizer? One of the most confusing terms in the field of air purification is the air ionizer. In one advertisement after another we find air cleaning devices with widely varied technologies claiming to ionize the air. So just exactly what are we talking about when we use the term “air ionizer”.
The one thing that all these air cleaning devices have in common is they are a form of electronic air purifier. Electronic air purifiers use a high voltage wiring system to create an electrical charge that results in particulates passing through becoming negatively charged.
But after that the similarity ends and a whole host of differences begin to show up. Some use collector plates and some don’t. Some have a fan and others don’t. Some use a charged media filter and others use various mechanical filters including HEPA type filtration. Some use the ionization potential to deliberately create ozone and some attempt to reduce ozone byproducts with catalysts. Finally, there are the hybrids that mix and match approaches, sometimes including as many as five different technologies.
It’s no wonder that comparing air ionizer air cleaners is confusing. How can you know what is effective? Are there any that should definitely be avoided?
The vast field of products renders it ridiculously difficult to evaluate air ionizers individually. However, it is possible to break down the basic technological approaches used and determine if any one or combination is worthwhile.
The primary technologies found in air ionizer devices are:
- The electrostatic precipitator
- The negative ion generator
- The ozone generator
Each of these receives a brief overview below.
The electrostatic precipitator
The electrostatic precipitator uses a series of collector plates with a charge opposite that of the ionized particles. This results in a powerful electrostatic attraction that pulls the particles to the plates like a magnet.
It is possible for particles as small as 0.1 micron to be collected this way. Since this is smaller than the 0.3 micron rating of HEPA filters you will sometimes see claims that these devices are better than HEPA. However, it must be pointed out that even the best electrostatic precipitators are only 80% efficient. Compare this to the 99.97% efficiency of a HEPA filter.
Apart from the poor initial collection efficiency is the additional flaw that the plates progressively lose efficiency as material is collected. Research shows that in as few as three days you can lose as much as 80% of the collection efficiency of clean plates. This means your electrostatic precipitator will only be attracting about 20% of the particles passing through it. Regular maintenance cleaning is an absolute necessity. At a minimum, the collection plates should be cleaned twice a week and every day would be best in order to achieve maximum efficiency.
On a final note, electrostatic precipitators will produce ozone in sufficient quantities to be an irritant to many people, especially those with pulmonary related illnesses like asthma.
The negative ion generator negative ionizer no collector and brief faults
The ozone generatorozone generator and faults
Eleven ways air ionizers underperform
- Low efficiency. Even the best models only achieve 80% efficiency at particle removal. They are unable to clean the air to HEPA standards.
- Rapid loss of efficiency. Loading of collector plates with captured particles rapidly degrades efficiency at collecting further particles. Efficiency can be reduced to below 20% in as few as three days.
- Constant maintenance. The rapid reduction in collection efficiency due to plate loading requires regular maintenance cleaning. From twice a week to daily is recommended, depending on the environment.
- Reduction in efficiency over life of unit. Even with regular maintenance cleaning, collection efficiency will degrade as constant bombardment from high energy ions corrodes the needlepoint ionizers or ionizing wire.
- Short life. Corrosion of the ionizing wire or needlepoint ionizing pins by ion bombardment will result in failure of the air ionizer. Hence, short warranties.
- Ozone production. All air ionizers produce ozone, a hazardous gas that damages the tissues of the airways causing increased sensitization to allergens, difficulty breathing for asthmatics, and possible severe respiratory distress.
- Limited coverage area. Government regulations on ozone exposure levels effectively requires manufacturers to balance the ionization potential of their units against the level of ozone produced. This serves to limit the area an ionizer can effectively clean. This means that you must buy multiple units to achieve the same coverage area as a single HEPA purifier may be capable of handling.
- Limited area, part II. Low air flow. The need for ionized particles to spend sufficient time in the air ionizer to be deflected onto the collection plates means air speed must be slow. Thus, air ionizers often use no fan or a low speed fan. Low air flow means low air volume handled by the unit and thus significant limitations on the size of the area that can be cleaned. Again, you must buy several units to achieve the coverage of a single HEPA air purifier.
- No effect on gaseous contaminants. Chemical toxins, mold mycotoxins, volatile organic compounds, formaldehyde, the hundreds of chemicals in cigarette smoke all pass through an air ionizer unaffected.
- Black wall effect / Black lung. Ionized particles not collected on plates in the electrostatic precipitator or by design with a negative ion generator will instead collect on walls, furniture, or any available surface. This includes the inside surface of your lungs. This effect has been given a name. It’s called the black wall effect. The health hazard of negatively charged respirable particles adhering to your lung tissues has been noted by the EPA. See: Possible effects of particle charging
- Arbitrary pricing serves as no guide. Testing often shows that high priced models may perform no better or even worse than cheaper ones. Quality of materials and construction, durability, and effectiveness do not seem to play a consistent role in pricing. Rather, it seems the basis for price is simply what the market will bear for the promise of clean air. This situation is often pointed out by the sellers of air ionizers themselves.