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"Life in Japan" Plasmacluster and nano-e have no sterilizing effect! About the Dark Side of Air Purifiers

Each of them emits special substances called plasmacluster ions and nano-e particles into the air, which are said to have inhibitory effects on airborne bacteria, environmental bacteria, and airborne viruses, and are installed in many electrical appliances. But is this true?

Papers experimenting with this case

Upon further investigation, we found that Dr. Shuichi Nishimura of the Virus Center, Department of Clinical Research, National Hospital Organization Sendai Medical Center had conducted experiments and written two papers. (I could not find any other papers by other authors.) The abstracts are as follows

Verification of the Effectiveness of Various Air Purifying Electrical Products Claiming Bactericidal Power against Bacteria in the Dry State of Application 2012 (April 3, 2012)

Assuming bacteria adhering to environmental surfaces in a dry state, various bacteria were applied to glass slides and placed in a glove box with a volume of 0.2 m3, and the number of viable bacteria was quantified after the subject model was operated for a certain time.

The amount of viable bacteria was almost the same for all models and all bacterial species, and little bactericidal effect was observed.
Analysis of the bactericidal activity against bacteria on agar plates of various electrical products that claim to emit airborne substances with bactericidal properties

Analysis of the main body of bactericidal capacity against bacteria on agar plate doubled ground of various electrical products claiming to release airborne substances with bactericidal performance June 22, 2012

There are several electrical products on the market that claim to inactivate viruses and sterilize bacteria in the environment by releasing a special substance into the air, and they also claim sterilizing effects on bacteria applied on agar plates. Therefore, we applied a certain number of bacterial solutions containing viable bacteria on ordinary agar plates, placed them in a closed space of 14.4 m3 together with the subject device, let the device run for 2 hours, and then incubated it, comparing the number of colonies that appeared with that of a control device placed in a non-operating environment.

The number of colonies formed was the same for all three models examined (Plasmacluster, Nano-e, and Bion) and for all four combinations of bacteria.

On the other hand, when the same experiment was conducted by placing agar media coated with bacteria in a sealed glove box with a volume of 0.2 m3, all three models reduced bacterial colony formation compared to the target, while Pseudomonas aeruginosa was not reduced. The possibility that the ozone emitted by these devices was responsible for the mechanism of colony formation inhibition/sterilization was investigated. The results showed that the bactericidal effect remained unchanged when the ions and special particulates they generated were removed, while the effect was drastically reduced when ozone was removed.
Analysis of the bactericidal activity against bacteria on agar plates of various electrical products that claim to emit airborne substances with bactericidal properties



Plasmacluster and nano-e themselves have no sterilizing effect, and in a very small space, it is clear that they are sterilized by the accompanying ozone that is emitted. Ozone is also a cause of air pollution because of its strong oxidizing power, which can have adverse effects on the human body.For more information, please refer to the following article.


About HEPA Filters

On the other hand, it is also true that there are rooms where the air is purified, called clean rooms. Such rooms are cleaned by HEPA filters (High Efficiency Particulate Air Filter) that collect dust and fine particles in the air. The JIS standard defines a HEPA filter as "an air filter that has a particle collection efficiency of 99.97% or higher for particles of 0.3 μm in diameter at the rated airflow rate and an initial pressure drop of 245 Pa or less.

How does a clean room work? |Clean Room at Comany


As one can easily imagine, the finer the filter, and the more dust and particulates it traps in the air, the less airflow it provides. Therefore, the frequency of HEPA filter replacement is very high, unlike filters for air conditioners and other devices that we use in our daily lives. The website of Kamata Kogyo Corporation, which designs and constructs clean rooms, explains as follows

Q.What is the standard time to change the filter?

A. Depending on the installation environment, periodic replacement is required for 3 to 5 years in locations with a good air supply side environment, and for 6 months to 1 year in locations with a poor air supply side environment.
What is the standard time to change the air filter? | KAMATA KOGYO Co., Ltd. provides integrated solutions and design/construction services for clean rooms


What about air purifiers, on the other hand? Sharp's website explains it as follows

Electrostatic HEPA filter*3 that collects over 99.97%*1 of particles as small as 0.3µm

HIt is a high-performance filter that sucks in 10,000 microscopic particles and allows only 3 to pass through, requiring no replacement*2 for 10 years*4. In addition, it is electrostatically charged, making it difficult to clog.


*1 This is the removal performance of the filter. It is different from the removal performance for the entire room.
*2 Depending on usage conditions, the life of the product may be accelerated.
*3 This filter collects over 99.97% of particles as small as 0.3 µm (micrometer).
*4 Calculated by the test method based on the Japan Electrical Manufacturers' Association standard (JEM1467), based on 5 cigarettes smoked per day. Depending on usage conditions and the type and intensity of the odor, cleaning or replacement may be necessary.
Features | KC-L50 | Air Purifiers: Sharp



It reads as if the various annotations avoid stating the sterilizing effect in the actual use environment. Among other things, we feel that "no need for replacement for 10 years" is greatly exaggerated. It also says "care and replacement," but the HEPA filter is made of glass fiber filter paper, so if you vacuum it, the fibers will likely break down in an instant. Realistically, replacement is the only option.

To begin with, how much area is covered by a HEPA filter? Searching for HEPA filters on Monotaro, the cheapest costs about 10,000 yen, and the most expensive costs about 50,000 yen. On the other hand, a single air purifier unit costs about 15,000 yen at the lowest price. Assuming that HEPA filters are really used, the only way to achieve this price would be to make the area of the HEPA filter much smaller or thinner.

Why do hospitals and hotels have air purifiers?

To begin with, even if air purifiers equipped with plasmaclusters and nano-e are effective in sterilizing air, air circulates on its own, as evidenced by the fact that people do not suffocate even when the house is closed off. Hospitals and hotels are even more ineffective at sterilizing air because of the large number of people who come and go. Then, why are air purifiers installed in many of these facilities? I think it is because patients and guests believe in the sterilizing effect of air purifiers.

Air purifiers are a hit product, selling more than 100,000 units per month, and home electronics retailers offer a wide selection on their main sales floors. Just as the common cold is not cured by medicine, but is prescribed because patients believe it can be cured by medicine and want it, hospitals, hotels, and other institutions are likely to have air purifiers because their patients and guests believe in them. While patients and guests are relieved, though, they often suffer from bad odors because the filters are full of bacteria. If it has a humidification function, even more so.


To sterilize your surroundings and prevent hay fever

So how can we keep our surroundings as sanitary as possible? The answer is to disinfect with alcohol or hypochlorous acid.

As for hay fever, since it is difficult to prevent pollen from being brought into the house, the only way is to suppress the symptoms through medication. As I wrote in a past article, I recommend Kunihiro's Rhinitis Medication A.


Vacuum frequently rather than buying an air purifier. Don't blindly believe what the manufacturer says; buy only what you really need.

I hope the above is helpful.