Ionic Air Purifier Technologies – Who Is Telling The Truth?
Introduction
Ionic air purifiers hold the promise of clean air, purified of all known harmful contaminants that threaten our health. The harmful impurities in the air are not visible to our naked eye. Invisible weapons against invisible enemies seems the obvious answer. Intuitively, the logic is compelling. Unfortunately, there is no simple solution as google throws up an avalanche of controversy within seconds. Obviously, I must resist the urge to go by intuition and grab the first ionic air purifier that I lay hands on. Effectiveness is important but safety is paramount in the criteria for selecting 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. This is especially so where the key reactive agent is invisible to the naked eye. Invisible ions produced by ionic air purifiers are clearly in this category.
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 prime threat being closely monitored by scientists all over the world 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 typically means that impure air is drawn into the air purifier for the reactive agents to work on before re-emerging as cleaned air into the environment. Conversely, in active mode, reactive agents are pumped into the impure air environment. It is not unusual to find combinations of both passive and active modes in many ionic air puriifers.
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 this happens, hydroxyl is produced. Commonly known as nature’s detergent, hydroxyl is a powerful reactive species that destroys airborne particulates by removing hydrogen molecules from their organic structures. Harmless by-products, mainly water, are generated by this chemical reaction.
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 real state of the natural environment. In contrast, proponents of negative ions technology insist that negative ions fill natural habitats and that the presence of positive ions is harmful. In this regard, I have yet to find independent scientific studies as evidence for the contradictory claims of both camps.
Ion Generator – Negative Ions
The traditional ionic air purifier produces only negative ions. Currently, this technology dominates market share but it is under serious threat from Sharp’s plasmacluster positive and negative ions technology.
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. Thereafter, simple vacuuming removes these impurities. Critics of negative ion technology charge that the weighed down particulates are not destroyed and the mere act of walking around the room kicks them back into the air that we breathe.
In addition, there appears to be several methods of producing the negative ions. It is critical to know the various methods as each may have different by-products, some harmful and some which are not. These methods include:
(1) Water method – this employs what is known as the waterfall or Lenard Effect. Water droplets are splashed onto a metal plate where a small electric charge is applied. Large numbers of negative ions are produced as water droplets are split. 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. An advantage of this method is that no ozone is produced. 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. A very high voltage is applied between the two electrodes. The movement of electrons between the electrodes ionises the air in that same space. 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. It relies on the production of the powerful reactive agent, hydroxyl.
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.
It is claimed that the comprehensive defence that POC provides is its main strength. 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 and ethylene all common emissions from everyday products of our modern home.
POC technology has been criticised for relying on hydroxyl which are believed to attack with equal tenacity the organic structures that make up molecular contaminants and our lung tissue, nose membranes and eye cornea.
Electrostatic Filter
This technology appears to have originated in heavy industries which produced abundant pollutants. Typically, an electrostatic filter is made of a porous dielectric material that is positioned between two electrodes. Dielectric materials do not conduct electricity while metallic electrodes are excellent conductors that transmit and receive electricity.
As impure air is drawn into the electrostatic purifier, it passes through the dielectric material which acts as a sieve. Electrostatic forces between the electrodes causes airborne particulates i.e.smoke contaminants, dust, etc, to adhere to the dielectric surface. Out of the other end of the purifier, cleaned air is recirculated.
Quite often, an ion source is placed before the electrostatic filter to impart an electric charge to the airborne particulates. These impurities, so charged, stick more effectively to the dielectric material.
The general criticism of ionisation technology applies to electrostatic filters as well i.e. that harmful ozone is a by-product.
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. I have barely skimmed the surface of the safety issues of each technology. I will also be studying in detail the claims of each technology. It is natural to want to quickly want something that promises to improve the air quality in your homes, offices, factories, schools etc. But I urge you to do your homework and don’t forget to visit me for updates as I continue my search for the ideal ionic air purifier.
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