Ionic Air Purifier Technologies – Boon or Bane?

Introduction

air ionizer" href="http://www.ionic-airpurifiers.com/">Ionic air ionizers 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. The weapons against such are very likely to be invisible to our eyes as well. Intuitively, the logic is compelling. Sadly, google has no quick answer to meet my simple expectation. Instead, controversy abounds. Even though I am tempted to quickly get an ionic air ionizer 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 ionizer.

The recent China melamine saga that killed infants also serves as a 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. My investigation of ionic air ionizer technologies falls within this realm, as the reactive agents are ions that are invisible to our eyes.

This article is an overview of existing ionic air ionizer technology in the marketplace. As laypersons, I believe we have to adopt a back-to-basics approach to try and understand the technologies. A dominant current trend appears to be the creation of an invisible but potent defence shield against airborne molecular contaminants. The predominant airborne threat being monitored by scientists the world over 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. Under passive technology modes, reactive agents are contained in the air ionizer whilst impure air is drawn in for cleansing before being pushed back to the environment. Active mode depicts the proactive process of bringing the purifying reactive agents into the surrounding impure air. 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 ionizer 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 air ionizer" href="http://www.ionic-airpurifiers.com/">ionic air ionizer technology. They have been named as plasmacluster ions by Sharp Corporation, the Japanese corporate powerhouse that invented them.

Positive and negative plasmacluster ions actively surround harmful bacteria and viruses in a deadly embrace. When clumping occurs, 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. This chemical reaction generates harmless by-products, the main of which is water.

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. 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 ionizer produces only negative ions. This technology appears to have the main market share currently but is facing a serious challenge 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. Negatively charged ions are naturally attracted to these particulates until they sink to the ground by sheer weight. These impurities are simply removed by vacuuming. 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. The charge splits the water droplets resulting in the production of a large number of negative ions. No harmful by-products result from using the water method to produce ions.

(2) Electron radiation method - this is based on a single negative discharge electrode needle. The simple application of a high voltage pulse to the electrode results in millions of negatively-charged electrons being produced. 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. High voltage is applied between the electrodes. This causes the movement of electrons between the electrodes thereby ionising 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.

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. biological compounds that may be infectious or contagious (e.g. pathogenic bacteria and viruses) or non-infectious and non-contagious (e.g. non-pathogenic bacteria, molds, cell debris)

(3) volatile organic compounds (VOCs) i.e. gaseous odours and chemicals - toluene, chloroform, hexane, ethanol, formaldehyde, ethylene etc, 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. The typical electrostatic filter ionic air ionizer 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.

As impure air is drawn into the electrostatic purifier, it passes through the dielectric material which acts as a sieve. Electrostatic electricity between the electrodes causes airborne particulates i.e.smoke contaminants, dust, etc, to stick to the dielectric surface. Purified air emerges from the other end of the purifier.

An ion source is often 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.

Criticism of electrostatic filter technology focuses on ozone as a by-product, commonly assumed to be produced in all ionisation processes.

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 ionizers to enhance VOC elimination;

(3) reducing catalysts such as manganese dioxide are coated near the exit outlets of many air ionizers 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 ionizer 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 ionizer involves analysing a deluge of information. The safety issues of each technology will need much more investigation. I have also not examined in greater depth the claims of each technology. I urge you not to rush out to get the latest air ionizer 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 ionizer.

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Ionic Air Purifier Technologies – Boon or Bane?

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