Indoor air pollution is becoming a serious problem. Most homes have airborne concentrations of hazardous and toxic chemicals two to five times higher than outdoors. Today’s building methods demand higher energy conservation have created super-insulated airtight indoor spaces. Lower heating and cooling costs result, but pollution gets trapped inside.

Some technologies including most air ionisers produce ozone as a by product of the cleaning process and some technologies, namely ozone generators actually use ozone as part of the cleaning process. However the use of ozone  in an air purifier product has become highly controversial due to the harmful effects ozone has on the respiratory system.

"When inhaled, ozone can damage the lungs. Relatively low amounts can cause chest pain, coughing, shortness of breath, and, throat irritation. Ozone may also worsen chronic respiratory diseases such as asthma and compromise the ability of the body to fight respiratory infections. People vary widely in their susceptibility to ozone. Healthy people, as well as those with respiratory difficulty, can experience breathing problems when exposed to ozone." U.S. Environmental Protection Agency

What is Ozone?

Ozone is formed naturally in the atmosphere, as a colorless gas and has a very pungent odor. In the upper atmosphere Ozone filters potentially damaging ultraviolet light from reaching the Earth's surface and is present in low concentrations throughout the Earth's atmosphere.

Ground-level ozone however is an air pollutant with harmful effects on the respiratory systems of animals. Quite simply, ozone is a very active form of oxygen, consisting of three atoms instead of the normal two. The triple bond of ozone is quite weak and one atom needs to be shed to make it stable again. So when it passes near another single oxygen atom or another (triple atomed) ozone molecule, the surplus (loose) atoms will break away and re-combine into oxygen pairs.

What are the effects of Ozone?

Studies have shown that people living in communities where there are high ozone levels have worse lung functions over five years than people living in communities with lower levels of ozone. Long-term exposure to ozone can impair lung function and cause structural changes to the lungs. Ozone is an indoor air pollutant because it is an irritant to the eyes, nose, throat and lungs.

Health Problems Associated with Ozone

There are many factors that determine if one might become ill due to exposure to ozone. These include:

• The concentration of ozone. Very low concentrations of ozone can be harmful to the upper respiratory tract and the lungs.

• People who have pre-existing lung problems, such as emphysema, bronchitis, or asthma, are even more at risk for the effects of ozone. Children also appear to be more susceptible to the effects of ozone.

• Ozone can increase one's sensitivity to allergens.

• Ozone can irritate the eyes, nose, and throat. Higher exposures to ozone (0.25 ppm to 1 ppm) may result in cough, shortness of breath, dry throat, wheezing and reduced lung function:

• Do not use ozone generators as air cleaners. The Federal Drug Administration (FDA) in the US has said that in order for these devices to be effective, they would need to create a concentration of ozone much higher than can be safely tolerated by most people. Concentrations from ozone generators range from 0.2 ppm to 2 ppm5, which is high enough to produce health effects.

How much Ozone is safe?

If you've worked in an office, you'll almost certainly recognise the smell of ozone - it's that smell that comes out of the photocopier and laser printer. That's because they use static electricity to transfer the toner powder into an image on paper. And anything that uses high voltages in this way has a tendancy to produce ozone.

When building high voltage equipment it's very easy to generate ozone - almost as a by-product. It is actually much harder design equipment that doesn't produce it. Maybe that's why many ionizer manufacturers try to sell ozone as if it were somehow beneficial. It is important to be aware that a badly designed ionizer may produce ozone, and with it nitrous oxide. The WHO (World Health Authority) guidelines, say that the maximum acceptable level of ozone is 0.1ppm (parts per million). Also, the ionizer's emitter needles can deteriorate severely in the presence of ozone. In other words, if the ionizer generates ozone, it will need to have it's needles replaced quite often.

When you are buying an air purifier it’s important to check whether the product emits ozone. Many products on the market that claim to be filters are actually hybrid technologies that combine the cleaning technologies of an air ioniser and a filter. These, and all other products should be clearly marked to show what levels of Ozone they emit. If you are not sure check with the sales managers or with the manufacturer.