I recently came across portable negative ion air purifier that you can simply wear around your neck.
A model I looked at demonstrated, in their promotion video with an air ion counter, that it can produce an average of 10 – 18 million negative ions per cubic centimeter.
I came up with the following pros and cons at the time.
Pro: high negative ion output, lightweight and portable, convenient, low maintenance,
Con: finite life (2-3 years at most) but being electronic, can be prone to breakage; potential harmful ozone output as byproduct; battery operated; absorption is only through breathing; Cost ranges from $75-$300 each;
Hong Kong’s TVB News recently reported that the Hong Kong Consumer Council conducted testing of ten portable negative ion air purifiers (made in China, Taiwan, Japan and Korea) and the results indicated that none performed at the level that the manufacturers claimed.
Here’s the link to the news on Youtube (in Cantonese). I have attached the translation of the video descriptions that gives a summary of the findings. I have also found the reporting from the Consumer Council’s website.
After watching and reading the reports, here are my understanding:
- Testing include ozone concentration, negative ion density, bacterial removal ability, and PM2.5 removal ability
- Maximum effectiveness score is 5 and the best two models performed at a 3 with the rest at 2.5 or less.
- Large variations in negative ions generated which ranged from a low of 2000 to as high as 660,000 negative ions per cubic centimeter (ions/㎤)
- After placing in a sealed space for 2 hours, 6 models can only remove less than 15% of the PM2.5 contaminant. Even the top 2 models took 2 hours to remove 90% of the contaminants.
- Testing environment that is small and sealed is not the same as the actual user environments that are often large and open.
- Negative ions generated by the purifiers can be blown away from the users, losing its intended benefit.
- Constant change in air makes it difficult to purify air the users breathe in.
- Because pollutants are often light, even after they have deposited onto surfaces, they can float back up in the air creating secondary pollution.
- Negative ion technology is more suitable for air purifiers used for a controlled indoor environment such as medical facilities. More schools, gyms, and offices are also starting to employ this in their HVAC system.
A very important finding is that the test results does revealed that “models generating lower negative ion density generally performed poorer in the bacterial removal and PM2.5 removal tests.”
This is in alignment with the importance of density in order for negative ions to work for the body. The higher the density, the better the effect. If you have not seen our presentations regarding the 3 key success factors, opt in to get our 3 part video series to learn more.
Also very importantly, use of the air purifier does not leverage the ability of the skin, the largest organ in our body, to breath/absorb negative ions like clothing and bedding products can.
Hong Kong Consumer Council tested ten portable negative ion air purifiers with disappointing sterilization performance-20200915-TVB News
The Consumer Council tested ten portable negative ion air purifiers on the market. All of them performed unsatisfactorily. The sterilization performance was even more disappointing. The Consumer Council urged consumers not to blindly rely on them.
With the new coronavirus epidemic, many people use neck-mounted air purifiers, which claim to produce negative ions to purify the air. The Consumer Council tested ten of them on the market with prices ranging from about HK$600-1,700 (US$77-$219).
The concentration of negative ions is directly related to its ability to remove bacteria and pollutants. The Consumer Council found that the concentration of negative ions in the samples ranged from 2,000 to 660,000 per cubic meter centimeter, a difference of nearly 330 times across different models.
Placed in a small sealed space of 1.5 cubic meters, it was sprayed with Staphylococcus aureus. After using the purification machine for one hour, all the samples could not completely sterilized the bacteria, and the most effective can only sterilized about 80% of the bacteria.
As for the ability to remove PM2.5 pollutants, the sample is placed in a sealed space of 3 cubic meters. Two models can remove 50% of the pollutants in the first half an hour, and 90% after two hours. Six models can only remove 2% in the first half an hour and less than 15% after two hours. With a maximum possible score of 5, these six samples scored only 1.5 points whereas the highest score of one of the ten model was only 3 points.
The Consumer Council pointed out that in the actual open environment, the efficacy of this type of purifier is questionable, and consumers should not blindly rely on it.
The Director-General of the Consumer Council Huang Fengxian said: “Negative ions can produce negative ions from nearby pollutants or bacteria, attract them, and then settle. Because the particles in the air are very small and light, they will be fly around when the wind is blowing causing secondary pollution. She advised not to use it as a “talisman,” and hang on to this negative ion machine to make you feel at ease. The reason is that the difference between the environment mentioned by the manufacturer and the actual user environment is too big.”
Regarding the performance of the test inconsistent with the manufacturer’s claim, the Consumer Council stated that it has been handed over to the customs for follow-up.
TVB Anywhere Life, 2020, September 15, https://youtu.be/8MNSzMzCP3s.
Hong Kong Consumer Concil. 2020, September 15. Wearable air purifiers had only limited effects. Consumer Council. https://www.consumer.org.hk/ws_en/news/press/527/wearable-air-purifier.html
Original Chinese description:
香港新聞 消委會測試十款隨身負離子空氣淨化機 除菌表現令人失望-20200915-TVB News 消委會測試市面十款隨身負離子空氣淨化機，全部表現未如理想，除菌表現更令人失望，消委會呼籲切勿盲目依賴。 新冠肺炎疫情下，不少人使用掛頸式空氣淨化機，這類淨化機聲稱可產生負離子，從而達到淨化空氣效果。消委會測試市面其中十款、售價介乎約600元至1700元。 負離子的濃度與除菌及污染物能力有直接關係。消委會發現樣本的負離子濃度每立米厘米介乎2千個至66萬個，相差近330倍。 放在1.5立方米的細小密封空間，裡面噴灑了金黃葡萄球菌，使用淨化機一小時，全部樣本未能徹底除菌，最多的只可除菌大約八成。 至於去除PM2.5污染物的能力，樣本放在3立方米的密封空間，這兩款首半小時可去除五成污染物，兩小時後可去除九成；這六款首半小時只能去除百分之2污染物，兩小時後去除率不足一成半，以5分為滿分，這六款樣本評分僅得1.5分，最高分的亦只得3分。 消委會指在實際開放環境下，這類淨化機的功效成疑，消費者切勿盲目依賴。 消費者委員會總幹事黃鳳嫺指：「負離子將附近污染物或細菌產生負離子作用，吸住他們、然後沉降也好。因為空氣中的微粒很小及很輕，有風又會吹起，很容易有二次污染。大家不要當成『護身符』，亦不要想掛著這負離子機令你安枕無憂，原因是廠商說的環境及實際使用環境的差距實在太大。」 對於測試的效能與廠商聲稱的不符，消委會指已交予海關跟進。