For the past 30 years a number of technologies have been tried in the attempt to remove airborne particles. A wide variety of air filtration systems or air purifiers have been developed and marketed with claims of total removal of harmful airborne contaminants and with no need for any type of air filter; using only simple techniques.
Two of the most common air purification devices that fit this description are air Ionisers ( or negative ion generators) and ozone generators. Ion generators use high voltage to electrically charge air molecules. Negative ions are particles with one or more extra electrons. Ozone generators are designed to attract an extra oxygen ion to an O2 molecule, using either a corona discharge or UV light.
Ozone generators were discussed in one of our previous blogs, so this blog will discuss the pros and cons of using ion generators as air purifiers.
Air ionisers work in this fashion. Airborne particles are attracted to the electrode in an effect similar to static electricity. These ions are de-ionized by seeking earthed conductors, such as walls, ceilings, nails in walls, etc. In essence the airborne particles are negatively charged and then find a positively charged surface and stick to it. (basic high school physics)
Perhaps another way to view this concept is to think about running a comb through your hair and then placing the comb next to tiny pieces of paper and watch the paper stick to or be attracted to the comb. This is how the ioniser works. Negative Ion Generators are also referred to as Ionizers (spelled with a z)
Here is the challenge with this technology. In every home and enclosed occupied environment there are always particles floating in the air. For the most part you can’t see these particles because you can only see particulate that is 20 microns in size or larger with the naked eye. Almost all of the airborne particles ( very light) are less than 10 microns in size (many less than 5 microns) and invisible to you.
For discussions sake let’s say that you can see all these airborne particles in your home as dark floating particles. When you turn on the ionizer the negatively charged air molecules will attach to the particles and then attach to or “plate out” to the walls, ceilings and any other surface. So now the dark particles are no longer airborne, they are now on the walls and other surfaces. They have not been removed from the room, just moved to another location.
The issue here is that negative ion devices are marketed as air purifiers, making the assumption that these systems will actually assist in removing or reducing harmful airborne particulate without the use of any filtering component or device. Nothing could be further from the truth. Once the electrical charge on the particle has dissipated, the particle becomes airborne again.
The only way the ionizer can be effective is to use it in conjunction with a air filtering device that actually uses a mechanical media filter. Otherwise you will never capture the particulate.
Pure Air Systems makes a complete line of HEPA based and media based air filtration systems and mechanical air filters. The new HPS series portable HEPA units are extremely effective at completely removing harmful airborne particles as small as .012 microns. For more information on these systems please go to our website at: www.pureairsystems.com