Air quality is one of the top ten factors determining how long we will live, and so air cleaners, otherwise known as air purifiers, are becoming increasingly popular. They will be more important as our homes need to become more sealed to conserve energy. Also, there is a misconception that they are only needed in “polluted” areas. The World Health Organization safe limit for PM2.5 particle pollution in order to maintain health is now below the levels of PM2.5 in almost all the United States for which there is data.
To sell air purifiers manufacturers, naturally try to use technology which will differentiate their air purifiers from their competitors. It can be difficult for the consumer to know how significant these technologies are in improving the performance of an air purifier. One such example is “plasmawave®”(Winix) sometimes also referred to as “plasma cluster®” (Sharp) technology, so different manufacturers refer to this technology in different ways. I will refer to this technology as “plasmawave” for the rest of this article.
Plasmawave is an air cleaning technology which uses an electrical discharge to produce hydroxyl radicals, which then interact with particles to remove hydrogen atoms. This is useful for altering organic chemicals and will inactivate viruses but is ineffective at changing inorganic particles such as carbon from exhaust fumes.
From the point of view of human health, in the vast majority of cases, the most important factor is the number and size of particles in the air. The larger ones settle in the airways, the small particles reach deep into the lungs and settle in the tiniest airways, and the ultrafine particles can even enter the bloodstream. From the bloodstream, these particles can enter the brain and other organs in the body.
So from a health point of view, although chemical change of particles in the air can be useful, the change in number of particles in the air is crucial. So one way we can judge these technologies is by considering the reduction in airborne particles in the air.
The health effects of airborne particles are in general the most important aspect of the affect of air on health.
Please see this article on the health effects of air pollution for further details.
There are air purifying technologies which sound scientifically advanced but contribute do not add significantly to particle reduction when added to a standard HEPA fan/filter air purifier and are ineffective when used on their own.
So how useful is it to add plasmawave technology to an air purifier?
What even is plasmawave technology?
How Plasmawave technology works
The diagram below shows how plasma wave technology works. An electric discharge splits water molecules into hydrogen ions and oxygen ions. These then combine on the surface to form a hydroxyl radical. The hydroxyl radical will then steal a hydrogen from any molecule that it may come into contact with and form a water molecule. The molecule that lost the hydrogen atom becomes altered in this structure and will probably change shape, and cease to function, eg as a receptor on a virus.
How Effective is Plasmawave Technology?
Some airborne particles are formed of organic chemicals. Organic chemicals have as part of their constituents carbon hydrogen and oxygen. These can be altered by plasma wave technology, but usually not completely destroyed.
Other particles are formed of inorganic chemicals. Plasmawave technology cannot deal effectively with some important types of these.
Inorganic particles
A good example of inorganic particles, are the carbon particles in the exhaust fumes from internal combustion engines. As there is no hydrogen in these they will be largely unaffected by plasmawave technology.
However, these particles are known to have a detrimental effect on human health.
Organic Particles
Viruses
The prime example of organic particles that are usefully altered by plasmawave technology are viruses. Viruses are composed of proteins and nucleic acid. The proteins in the outer coat of the virus need to be a specific shape to latch on to receptors on their target cells, the cells in your body. When plasmawave technology creates hydroxyl ions which takes hydrogen atoms away from these proteins, the protein’s shape changes and it can no longer fit into the receptor on the cell the virus is trying to infect. So the virus is rendered inactive.
Bacteria
Bacteria operat in a completely different way from viruses. They do not need to latch onto cells and enter the cell. So damaging proteins on the surface is less likely to have an impact on bacteria. Many bacteria have strong cell walls that are resistant to damage.
Nevertheless bacterial reduction in the air is a claimed advantage of this technology.
Reduction in Odors
Most odors are caused by volatile organic compounds. These compounds are made of carbon hydrogen and other atoms. Removing hydrogen atoms from the volatile organic compounds will change their structure and hence the smell. So plasmawave by using hydroxyl ions to remove hydrogen atoms from molecules can reduce odors.
Reduce Mold Growth Rates
This is an interesting and important claim. Obviously it is potentially a useful feature. However it does beg the question that if mold growing on a wall can have its cell membranes damaged so that its growth is reduced does this have implications for our cell membranes? Obviously, we are quite likely to be nearer the air purifier with plasmawave technology, than the mold and so be exposed to a higher concentration of ions than the mold. What then might the affect of breathing them in have on the cell membranes of our lungs and mouth? Would there be an effect on our eyes?
Please see section below on safety.
Increases Air Purification Performance by Reducing Static Electricity
The ions produced by plasmawave neutralize the static electricity on objects in the room. So airborne particles do not stick to other objects before they get sucked into the air purifier.
This does of course implies a widespread dispersion of ions in the room so that anybody in the room is likely to breathe them in.
It also means that airborne particles will not be taken out of the air by being attracted by the static electricity.
Allergens
Allergens are often formed from organic molecules, for instance house dust mite or pollen. These allergens are enormous compared to the size of the ions produced and will have elements all over their surface which could trigger an allergic reaction. The plasmawave ions would have to coat and alter the proteins over the whole surface of the allergen to be effective.
So it is unlikely that plasmawave would be effective at preventing allergic responses, and indeed this is not what is claimed.
What is The Likely Effect of Plasmawave Technology on the Air in a Room as Regards Human Health?
Plasmawave treatment of air is particularly good at damaging particles but not anything like as good as removing particles from the air as a standard HEPA air cleaner. As outlined above, damaging particles is very helpful in the case of a virus as it will damage the receptors that allows it to invade cells. This renders the virus ineffective.
In addition, plasmawave cannot damage some particles, for instance carbon particles in vehicle exhaust fumes. Also other organic particles although damaged, will still be present in the air.
In the diagram below I have tried to show graphically why this matters. On the left of the diagram in the box is the air before purification, in the middle box after air purification with plasmawave treatment and in the right hand box after HEPA filtration.
Theoretically, HEPA filtration could get rid of all the particles. However, in practice, the modest clean air delivery rate of the air purifier and the fact that particles manage to enter the room, for instance through cracks around windows and doors, means that the actual particle reduction is much less.
How Effective is Plasmawave Technology?
Some airborne particles are formed of organic chemicals. Organic chemicals have as part of their constituents carbon hydrogen and oxygen. These can be altered by plasma wave technology, but usually not completely destroyed.
Other particles are formed of inorganic chemicals. Plasmawave technology cannot deal effectively with some important types of these.
Inorganic particles
A good example of inorganic particles, are the carbon particles in the exhaust fumes from internal combustion engines. As there is no hydrogen in these they will be largely unaffected by plasmawave technology.
However, these particles are known to have a detrimental effect on human health.
Organic Particles
Viruses
The prime example of organic particles that are usefully altered by plasmawave technology are viruses. Viruses are composed of proteins and nucleic acid. The proteins in the outer coat of the virus need to be a specific shape to latch on to receptors on their target cells, the cells in your body. When plasmawave technology creates hydroxyl ions which takes hydrogen atoms away from these proteins, the protein’s shape changes and it can no longer fit into the receptor on the cell the virus is trying to infect. So the virus is rendered inactive.
Bacteria
Bacteria operat in a completely different way from viruses. They do not need to latch onto cells and enter the cell. So damaging proteins on the surface is less likely to have an impact on bacteria. Many bacteria have strong cell walls that are resistant to damage.
Nevertheless bacterial reduction in the air is a claimed advantage of this technology.
Reduction in Odors
Most odors are caused by volatile organic compounds. These compounds are made of carbon hydrogen and other atoms. Removing hydrogen atoms from the volatile organic compounds will change their structure and hence the smell. So plasmawave by using hydroxyl ions to remove hydrogen atoms from molecules can reduce odors.
Reduce Mold Growth Rates
This is an interesting and important claim. Obviously it is potentially a useful feature. However it does beg the question that if mold growing on a wall can have its cell membranes damaged so that its growth is reduced does this have implications for our cell membranes? Obviously, we are quite likely to be nearer the air purifier with plasmawave technology, than the mold and so be exposed to a higher concentration of ions than the mold. What then might the affect of breathing them in have on the cell membranes of our lungs and mouth? Would there be an effect on our eyes?
Please see section below on safety.
Increases Air Purification Performance by Reducing Static Electricity
The ions produced by plasmawave neutralize the static electricity on objects in the room. So airborne particles do not stick to other objects before they get sucked into the air purifier.
This does of course implies a widespread dispersion of ions in the room so that anybody in the room is likely to breathe them in.
It also means that airborne particles will not be taken out of the air by being attracted by the static electricity.
Allergens
Allergens are often formed from organic molecules, for instance house dust mite or pollen. These allergens are enormous compared to the size of the ions produced and will have elements all over their surface which could trigger an allergic reaction. The plasmawave ions would have to coat and alter the proteins over the whole surface of the allergen to be effective.
So it is unlikely that plasmawave would be effective at preventing allergic responses, and indeed this is not what is claimed.
What is The Likely Effect of Plasmawave Technology on the Air in a Room as Regards Human Health?
Plasmawave treatment of air is particularly good at damaging particles but not anything like as good as removing particles from the air as a standard HEPA air cleaner. As outlined above, damaging particles is very helpful in the case of a virus as it will damage the receptors that allows it to invade cells. This renders the virus ineffective.
In addition, plasmawave cannot damage some particles, for instance carbon particles in vehicle exhaust fumes. Also other organic particles although damaged, will still be present in the air.
In the diagram below I have tried to show graphically why this matters. On the left of the diagram in the box is the air before purification, in the middle box after air purification with plasmawave treatment and in the right hand box after HEPA filtration.
Theoretically, HEPA filtration could get rid of all the particles. However, in practice, the modest clean air delivery rate of the air purifier and the fact that particles manage to enter the room, for instance through cracks around windows and doors, means that the actual particle reduction is much less.
Is Plasmawave Technology Safe?
Winix offers the following statement on the safety of plasmawave technology:
“Plasmawave® meets the California Air Resources Board’s AB 2276 standard, which is the most rigorous American certification benchmark for indoor air cleaning ozone emissions.”
This is reassuring and shows that the technology meets current rigorous standards regarding ozone. However, it does not address the issue of ion production, which is at the center of plasmawave technology.
It would be good to have data on the websites of manufacturers using this technology to use ions in the air showing that for instance –
Do ions reach human lungs or eyes in significant concentrations? Particularly, as one manufacturer states that this technology will reduce the growth of mold. So presumably ion concentration in the air is great enough to have a biological effect throughout the room.
If they do reach human tissue in a significant concentration, then there are no problems with any changes that occur in the tissue as a consequence.
It seems likely that the concentrations of the ions that we breathe in is so small or even zero so that the technology is perfectly safe. However, it would be great if the manufacturers would publish more information to show that this is indeed the case.
How is Plasmawave Technology Different From Other Technologies
So let’s look at the different technologies and see how they differ from each other. They are each discussed below and outlined in this diagram-
Photoelectrochemical Oxidation (PECO)
As is seen in the diagram above, PECO and PCO work by producing hydroxyl radicals which remove hydrogen atoms from molecules. These molecules can be part of larger particles. Removing hydrogen atoms will alter the structure and possibly the function of the molecules/particles but may well not destroy the particles. Therefore, this technology is not optimal for reducing particle count in the air.
The mechanism of PECO is very similar to plasmawave technology, except that the energy to form the hydroxyl radicals comes from UV light and a catalyst is used.
In a standard air purifier, activated carbon filters absorb both reactive and nonreactive VOCs. They do this to a modest extent but across a wide range of chemicals. One study showed that photo electrochemical oxidation (PECO) is the only other technology that will deal with both reactive and nonreactive VOCs. In this study, the CADR for removing both types of VOCs from the air by PECO reduced with increasing relative humidity, but was approximately 10 times that of an activated carbon filter. The problem was that PECO in this study was shown to produce formaldehyde and other carbon compounds which could potentially be a health problem. Both of which could also be oxidized further by the PECO.
Like plasmawave, PECO has not been shown to be very effective at reducing airborne particles, which are usually the most important air pollutant from the point of view of human health. So PECO could be a useful addition to a HEPA air purifier for removing chemicals, but is not currently recommended to deal with particles on its own.
PCO
PCO is a similar technology to PECO in that it produces hydroxyl radicals by UV light exciting a catalyst. The difference is that PCO uses a catalyst of titanium oxide or titanium dioxide.
UV
UV light directly damages DNA and RNA to stop living organisms growing and multiplying. It does not reduce airborne particles or chemicals significantly. This can be useful in an HVAC system for stopping fungal growth on the cooling coils. In this situation the UV is not there to destroy micro-organisms in the air but those stuck to the cooling coils. As they are stuck they are irradiated for long periods of time, long enough to damage their DNA.
This is shown in this diagram0
Ionic Air/Negative Ion Generator Purifiers
This technology simply gives an extra electron to particles, causing them to have a negative charge and become negative ions. These negatively charged particles are attracted to either the positive electrode, positively charged particles in the air, or positively charged objects in the room where they stick. In this way particles are removed from the air with a negative ion generator, however its action is not as reliable as a true HEPA filter.
Unfortunately, the particles are still free in the room and can be dispersed back into the air by being disturbed by human activity in the room.
For further details please see this article “Negative ion air purifier“.
Ozone Generator
Ozone generators, as their name suggests, produce ozone which then interacts with organic chemicals, damaging them. In this way, biological entities such as viruses and potentially then bacteria are inactivated. The problem is it also damages human tissue and so cannot be used safely where humans are present. Hence the strict Californian guidelines on acceptable amounts of ozone in the air.
This is exactly why it would be helpful if companies producing plasmawave air purifiers would point us in the direction of laboratory and ideally human studies that show that the technology is safe. It may well be entirely safe, but it would be good for the consumer to know that beyond reasonable doubt.
Conclusion
The best type of air purifier by far is the standard HEPA air purifier. This will remove all types of pollutant particles from the air, including viruses, bacteria, pet dander, smoke particles and allergens such as house dust mite and pollen. This type of fan and filter combination forms the most effective type of air cleaner. The fan speed determines the clean air delivery rate and hence the size of room that the air cleaner can serve.
Plasmawave technology is not adequate to remove particles on its own, but can be added to a standard HEPA air purifier. The reduction of virus or bacteria in the air cleaner itself is not essential as the filter in the air purifier will remove almost all viruses and bacteria. Plasmawave may have a role in reducing viral count in the air if it gets enough ions distributed into the air, but then these ions will also be able to interact with your lungs. As far as we currently know, plasmawave is safe.
So if the ions are largely confined to the air purifier they do not add anything essential and if they are widely distributed in the air, they can act on tissue in your body.
In addition, only a few air purifiers have plasmawave technology, and these may not be the best air purifiers for your specific need. So by choosing an air purifier based on the presence of plasmawave technology, you may be missing a better air purifier for your particular case.
I would advise simply buying an air purifier with a HEPA filter. I do own one with plasmawave technology, but I keep the plasmawave turned off.
