Ionic Air Purifier Technologies - Genius or Fraud?
Introduction
Ionic air purifiers hold the promise of clean air, purified of all known harmful contaminants that threaten our health. These harmful contaminants are not visible to our naked eyes. Invisible weapons against invisible enemies seems the obvious answer. Intuitively, the logic is appealing. Unfortunately, there is no simple solution as google throws up an avalanche of controversy within seconds. Even though I am tempted to quickly get an ionic air purifier to clean the air I breathe, it is clear that more time and effort is needed. Safety, more than effectiveness, must be given higher weightage in the selection of an ionic air purifier.
The recent China melamine saga that killed infants also is a timely reminder to us that in buying into any technology or any product, all claims by manufacturers and distributors must be screened to the fullest extent that our resources permit. Where the reactive agent is invisible, it becomes even more critical to focus on it. Investigating ionic air purifier technologies falls within this ambit as the reactive agents are invisible ions.
In this article, I am laying out the roadmap as I look into the existing ionic air purifier technologies in the global marketplace. Trying to understand the science behind the technologies seems to be the logical place to begin searching for the ideal ionic air purifier. The current key trend appears to be the creation of a potent invisible defence shield against airborne molecular contaminants that threaten our well-being. The dominant global health threat under the scrutiny of scientists is the avian flu virus.
Types of Ionic Air Purifier Technologies
Broadly speaking, air purification technologies can be deployed in either passive or active modes. Passive mode technologies incorporate means by which impure air is sucked into the air purifier for reactive agents to work on before being re-introduced into the environment as cleaned air. In active mode, the reactive agents are pushed into the environment with the impure air. Interestingly, marketeers betray their lack of confidence in their own ionic air purifier technologies by combining both passive and active modes.
In the global market today, ionic air purifier technologies include the following categories:
(A) Ion generator - positive and negative ions
(B) Ion generator - negative ions only
(C) Photocatalytic Oxidation (POC)
(D) Electrostatic filter
(E) Combos
Ion Generator - Positive and Negative Ions
This combination of positive and negative ions appears to show the most promise for the future of ionic air purifier technology. They have been named as plasmacluster ions by Sharp Corporation, the Japanese corporate powerhouse that invented them.
Sharp Corporation’s marketing efforts focus on the ability of plasmacluster ions to surround and cling on to harmful airborne bacteria and viruses. When clumping occurs, hydroxyl is produced. Known as nature’s detergent, hydroxyl is a powerful reactive species that plucks out hydrogen molecules from the organic structure of these airborne particulates, thereby killing them. The by-products of this chemical reaction, mainly water, are harmless.
A differential ion generator is used in this technology, comprising a positive and a negative ion generator which can be powered in alternate cycles to control the type of ions generated.
Advocates of the positive and negative ions combination claim that a balance of both these ion types is to be found in places like waterfalls and pristine forests, i.e. this is the actual state in nature. Diametrically, believers of the negative ions technology take the view that negative ions dominate the space in natural habitats and that positive ions are actually harmful. Thus far, I have not found any independent scientific studies to support the opposing claims of the two technologies.
Ion Generator - Negative Ions
The traditional ionic air purifier produces only negative ions. Apparently, negative ions technology dominates the ionic air purifier market at the moment but Sharp’s plamascluster technology is increasingly proving to be a serious alternative.
It is claimed that nearly all harmful airborne particulates like dust, smoke and bacteria etc have a positive charge. The positive charges are continually attracted to the negative charges of the ions until sheer mass makes them sink to the ground. Regular vacuuming removes these impurities from our environment. Detractors of negative ion technology believe that the “overweight” particulates on the ground are not destroyed and that the mere act of walking on them re-contaminates the air.
It seems that there are several ways to produce negative ions. It is crucial to know the various methods as each may have different by-products, some of which are harmful. These methods include:
(1) Water method - this employs what is known as the waterfall or Lenard Effect. Onto a metal plate that is electrically-charged, water droplets are splashed. This splits the water droplets, a process in which large numbers of negative ions are produced. It is claimed that no harmful by-products are produced by the water method.
(2) Electron radiation method - this is based on a single negative discharge electrode needle. Millions of negatively-charged electrons are produced when a high voltage pulse is applied to the electrode. This process does not generate any ozone. This is due to the application of a “smaller” energy pulse.
(3) Corona discharge method - this is based on a dual electrode model, a sharp metal electrode and a flat electrode. High voltage is applied between the electrodes. This creates a massive movement of electrons between the electrodes and ionises the air in between them. A criticism of this method is the production of harmful by-products like ozone and nitride oxide.
Photocatalytic Oxidation (POC)
This technology is commonly applied in a passive mode. In POC, the powerful reactive agent hydroxyl is also the key to the purifying process.
Germicidal ultraviolet (UV) light is commonly shone on a catalyst (usually titanium oxide) to produce hydroxyl, oxygen and peroxide, all of which are potent oxidising agents that are very effective at destroying the organic structure of micro-organisms and gaseous volatile organic compounds.
Complete and comprehensive action is the pillar of POC technology. Proponents of this technology claim that POC inactivates ALL categories of indoor pollution, including:
(1) airborne particulates i.e. dust, pet dander, plant pollen, sea salts, tobacco smoke, industrial and car pollution, etc
(2) bioaerosols i.e. contagious or infectious biological compounds (e.g. pathogenic bacteria and viruses) or non-contagious and non-infectious (e.g. non-pathogenic bacteria, molds, cell debris)
(3) volatile organic compounds (VOCs) i.e. gaseous chemicals or odours - benzene, styrene, toluene, chloroform, hexane, ethanol, formaldehyde, ethylene, etc, all common emissions from everyday products of our modern home.
Critics of POC zoom in on the power effects of hydroxyl, claiming that they cannot differentiate between the organic structures that make up molecular contaminants and our lung tissue, eye cornea or nose membranes.
Electrostatic Filter
This technology appears to have originated in heavy industries which produced abundant pollutants. The typical electrostatic filter ionic air purifier includes two electrodes sandwiching a porous dielectric material. Dielectric materials do not conduct electricity while metallic electrodes are excellent conductors that transmit and receive electricity.
Impure air is sucked into the electrostatic purifier and passed over the dielectric material which acts like a sieve. The electrostatic field created between the electrodes causes airborne particulates i.e.dust, smoke contaminants, etc, to stick to the dielectric surface. Purified air is pushed out of the purifier and re-circulated.
Frequently, an ion source is planted just before the electrostatic filter to electrically charge the airborne particulates. These impurities, so charged, stick more effectively to the dielectric material.
Critics of this technology point to the production of harmful ozone in the ionisation process.
Combo Ionic Air Purifiers
To cater to the various adherents and critics of the diverse technologies, combos incorporate all or some of the above types of technologies. Combos may include:
(1) adsorptive materials such as activated carbon or oxygenated charcoal (known for its extremely porous large surface area) are added to POC technology to enhance the removal of VOCs;
(2) oxidizing catalysts like titanium oxide are coated on various components of all types of air purifiers to enhance VOC elimination;
(3) reducing catalysts such as manganese dioxide are coated near the exit outlets of many air purifiers to reduce reactive species like ozone and nitric oxide which may be harmful;
(4) generating ions by differing methods such as using microwave, UV light, radio frequency waves, and direct current;
(5) tweaking the specifications of any ionic air purifier technology so as to attain the well-known HEPA status without actually using HEPA filters.
Obviously, the process of selecting the most efficient and effective ionic air purifier involves analysing a deluge of information. And I have not even touched on the safety aspects of each technology. I will also be studying in detail the claims of each technology. I urge you not to rush out to get the latest air purifier for your homes, offices, factories, schools etc. Do your homework and check back here for updates as I continue to find the ideal ionic air purifier.
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