Air pollution is one of the ten biggest global health threats as stated by the World Health Organization (WHO) due to it’s devastating toll of nearly 7 million death every year as consequence of related illnesses, be for people with preexisting conditions such as allergies or healthy ones [1]. This is mostly attributed to the burning fossil fuels as the main pollutant for outdoors spaces, but indoor air is 3 to 5 times more polluted than outdoors on average and as seen that we spend nearly 90 percent of our time indoors this issue is far more alarming.
Existing technologies
As of today, and during the development of air filters during the 20th century, High Efficiency Particulate Arresting (HEPA) filters have been the top of the line product used when cleansing air for medical rooms or when dealing with allergies at home. Air filters equipped with this technology can absorb up to 99.97% of all particles, like allergens pollen, dust, dander, and others that are 0.3 microns in size but with the current technology development new techniques are emerging that might out perform and revolutionize the industry. In this context many new technologies are being developed all over the world, generally trying to target more specific problems or even creating new technologies and systems as a whole to tackle the issue.
Photocatalytic Oxidation (PCO)
Among these two different technologies stand out from the rest, the first one being Photocatalytic Oxidation (PCO) [2]. This technology was first used by NASA when planning for deep space exploration as they needed to deal with the ethylene gas destroying plants and vegetables in the space shuttle. It was then, because of the impossibility of letting this gas flowing into the atmosphere as it would in earth that they came up with PCO. This principle focuses not on filtering or capturing the VOC in the air but on removing them by using titanium dioxide (TiO2) as a photocatalyst having the advantage of limiting the introduction of unconditioned air to the building space allowing to achieve energy savings when compared to other systems. The basic mechanism POC is that malignant organic contaminants would be oxidized into water, carbon dioxide or any inorganic harmless substances with OH or O2– radicals, which are generated around TiO2 under ultra-violet light irradiation [2].
Further test done by NASA revealed that it wasn’t only beneficial to eliminate ethylene gas but also to destroy all carbon-based impurities in the air such as: Bad Odors, Volatile Organic Compounds (VOC’s), mold, fungi, bacteria, and viruses [3].
This technology is currently used as both a portable unit for use in households and as a commercial in-duct unit system for large lab installations. PCO is not a filtering technology, as it does not trap or remove particles, so it is common to see it being used together with other technologies such as HEPA (high efficiency particulate air) in a multi-step process to remove other particles of up to 300 nm.
Photo Electrochemical Oxidation (PECO)
Following the PCO another emerging technology is a recently developed one by the company called Molekule created by Dr. D. Yogi Goswami, Distinguished Professor and the Director of the Clean Energy Research Center at the University of South Florida who has performed extensive research on indoor air quality [4]. The name of this technology is Photo Electrochemical Oxidation (PECO) which similarly to the previously mentioned PCO uses light to excite a nanoparticle coated filter, creating reactions on the surface of the filter that results in the creation of hydroxyl free radicals. They are then used to oxidize pollutants at the surface of the filter and converts them into harmless elements such as water or carbon dioxide. The main difference with PCO is that due to a patented innovative manipulation of the electron flow the PECO works orders of magnitudes faster than conventional PCO techniques, allowing the use of lower energy UVA radiation as the light source and thus, reduce the energy consumption while achieving improved performance.
The company responsible for its creation claims this technology can catch particles 1000 times smaller than the existing High Efficiency Particulate Arrestance (HEPA) which are considered some of the most efficient air filters used in hospitals. To back this up some studies performed by independent researchers proved than when measuring some of the most difficult pollutants to remove from air (0.02 nm) the PECO system vastly outperform preexisting technologies.
Many other tests were run confirming the superiority of PECO technology such as the removal of viruses, bacteria and mold, providing full spectrum of indoor air pollutants destruction [5].
This technology is now being implemented in home devices commercialized by Molekule as we can se in the picture below and consisting in a 4-part process at a price of 799$. As a first step the air intake is produce thanks to a small motor and in a 360º fashion to increase the air renewal rate and prevent stagnation in some parts of the room. Then a prefilter, most likely a HEPA although not specified captures the larger allergens and slows the intake of smaller VOCs to prevent the PECO system to saturate. Finally, the smaller particles are then run through the PECO filter to achieve the process explained above and result in clean air for the room without the need of outdoors ventilation.
Conclusion
Overall we can see how the evolution of HVAC filtration and air cleaning technology is following the right path of evolution to guarantee a better living environment for households, but have yet to see these new technologies implemented in buildings as a default setting and affordable prices to standardize this level of indoor air quality. Nonetheless, the emergence of the catalytic approaches is leading to better conditions especially for people with sensible allergies that were previously having harder times while indoors. More developments are being made in this sectors to provide a more personal approach to these issues such as the commercialization of wearables for improved personal outdoors and indoor air quality but the prices are sometimes very high and not accessible to all citizens even in the western countries.
REFERENCES
[1] Ten threats to global health in 2019https://www.who.int/emergencies/ten-threats-to-global-health-in-2019
[2] Huang, Y., Sai, S., Ho, H., Lu, Y., Niu, R., Xu, L., … Ho, W.-K. molecules Removal of Indoor Volatile Organic Compounds via Photocatalytic Oxidation: A Short Review and Prospect. https://doi.org/10.3390/molecules21010056
[3] AIR FOR LIFE LIMITEDhttps://www.airforlife.net/index.php?page=nasa_dev [4] D. Yogi Goswami | PhD | University of South Florida, FL | USF | Clean Energy Research Center. (n.d.). Retrieved April 15, 2019, from https://www.researchgate.net/profile/D_Goswami2 [5] PECO Technology Review
https://assets.molekule.com/Molekule+White+Paper+-+PECO.pdf