The NSW Health Department has warned against the use of ozone generators sold as air purifiers containing ionisers, and electrostatic precipitators. The fact sheet is available on their website:
http://www.health.nsw.gov.au/factsheets/environmental/ozone_generators.htmlThe fact sheet makes the point that “Terms such as "energized oxygen" or "pure air" suggest that ozone is a "healthy" kind of oxygen. However, ozone is a toxic gas with very different properties to oxygen….. ozone can be harmful to health.”
The effects of ozone on health
Ozone is a potent oxidant 100 times stronger than chlorine. Exposure to even low levels of ozone can aggravate asthma and commonly cause headaches, lung irritation, eye irritation and coughing.
How is ozone produced by ionisers and electronic air cleaners?
Ionisers and electrostatic air cleaners contain high voltage needles or plates which charge dust particles to stick to surfaces – the by-product of this process is a small amount of ozone being produced.
Do ionisers purify the air, do they remove dust or chemicals?
No. They have no filter or means by which they can capture dust or chemicals and are therefore commonly referred to as air cleaners and not air purifiers. As ionisers charge dust particles to stick to surfaces, people who use ionisers generally discover they have part of nearest wall to the ioniser being covered in black charged dust particles.. When these charged dust particles loose their charge the dust is released back into the room.
Some hybrid air cleaners contain ionisers or electrostatic ionisers that charge the air prior to passing through the filters. This causes the particles to be attracted to the filter media (post ionising process).
What is the problem with electrostatic ionisers being combined with HEPA filters in Hybrid air purifiers?
Other than issues with ozone production discussed above -ionisers and electrostatic air cleaners are used for one reason only: low manufacturing costs. They cost only a few cents to make and they are typically mass manufactured in China or a country where manufacturing costs are very low. It is cheaper for manufacturers of air cleaners to use high voltage needles than quality high efficiency HEPA filters and activated carbon filters which are proven scientifically to remove sub-micron dust and allergens or chemicals from the air.
A certified high efficiency HEPA filter is supposed to remove a minimum of 99.97% of particles 0.3 microns and larger. There are many cheap imitations of HEPA filters and these are what are used in hybrid air cleaners. An ioniser cannot achieve HEPA 99.97% efficiency, therefore the only reason these are used prior to a ‘HEPA’ filter is if the HEPA filter is not filtering at 99.97% efficiency or does not seal properly. There is no manufacturer in the world of medical rated HEPA air cleaners combining an ioniser in the filtration process.
Consumers who are looking for a serious air cleaner to address allergies, asthma, pollution issues or chemical sensitivities should avoid any air cleaner which uses an electrostatic ioniser.