UVC Air Purifier (UVGI)
UVC Air purifiers have been around for quite some time. It was tested in schools in Philadelphia in the 1930s. It has been frequently used in hospitals for the last 100 years. With recent events this technology has gained popularity. UV-C rays have a very particular wavelength. The light wavelength of 254 nm (nanometers) is particularly adept at disabling the DNA of microbial life forms.
Does UVC Filtration Work?
The simple answer is YES, however the process only works if a sufficient dose of UVC radiation is applied. Dose sounds simple enough, but it can be very complicated. To determine the dose you take the amount of UVC-Radiation multiplied by the residence time. For a more thorough explanation of this concept read more…
LAFC-RC2-HUV provides near 1000 CFM of ultra-clean air for schools, commercial and medical buildings. It features a True HEPA filter, a 30-watt UVGI filter, and 1 carbon filter. Each unit is tested for UVC safety and Ozone free operation. For ordering information see the link below.
LA2-RC1-HUV
The LA2-RC1-HUV provides 750 CFM of ultra-clean air for commercial and medical buildings. It features a True HEPA filter, a 60-watt UVGI filter, and 2 activated carbon filters. Each unit is tested for UVC safety and Ozone free operation. For ordering information see the link below.
LAFC-HUV Ceiling Mounted UVGI Air Purifier
The LAFC Ceiling Mounted Air Purifier has been popular since its introduction. We have created an upgraded model that includes a 30-watt UVC filter. The LAFC-HUV delivers a killing dose of over 1000µJ/cm² (micro joules per square centimeter) to any viruses or bacteria that might escape the HEPA filter.
LakeAir and UVGI
To legally manufacture products that use UVC technology for the removal of viruses, mold, or bacteria, a company must be registered as an EPA Pesticide Device Company. Any production of pesticide devices must be conducted in a registered pesticide-device-producing establishment. Our factory is a registered pesticide device producing establishment.
We have been working on adding UVC air filtration to our products since 2017. The biggest concern in developing this filter method has been safety. UV-C light can burn skin and injure the eyes. We design and test our UVGI for safety first.
In the spring of 2020, our company was contacted by a representative of Homeland Security. We received a request to develop a HEPA and UVGI hybrid air purifier to help in the fight against COVID-19. Our design team changed its focus from the current projects to a safe and effective HEPA / UV-C filtration product.
Early Testing
The previous target for UVC air purifiers had been our residential models. Containing sufficient UVGI filtration in such a small package was daunting to say the least. Our new focus would be for larger models that could accommodate UVGI safely along with high nano-particle entrapment. The following video shows the first successful test of our first UVGI prototype. This video was taken after midnight on one of many very long work days.
We have progressed from the first tests and now offer UVGI air filtration in several LakeAir models.
UVC Air Purifier is NOT a Standalone Filtration Method
UVC Air Purifiers have been in use for decades. While it’s widely known that UVGI kills all known microorganisms including bacteria, viruses, molds, and other pathogens, UVGI is not suggested as a stand-alone solution to microbial sanitation. The use of UVGI is termed an “effective adjunct” and that it should be used in conjunction with other filter technologies.
The image to the right is a UVGI Chamber used in the LakeAir LA2-RC1-HUV HEPA /UVGI Air purifier. This filter ensures any airborne pathogens that may have passed through the HEPA filter will be inactivated by a high dose of UV-C radiation.
What is UVC Dose ~ UVC Radiation & Residency Time
UVC dosage is determined by multiplying the amount of UVC Radiation by the residency time. To determine the amount of radiation you should use a professional UVC Meter to measure the actual amount of UVC radiation inside the UVC Chamber. Professional devices cost thousands of dollars and give accurate readings. We use a professional UVC Meter to test all of our UVGI Products.
UVC irradiance is expressed in a measurement called µW/cm² ( microwatts per square centimeter). Basically how much UVC radiation is put out by the bulb(s) in the UVGI device. The effectiveness (UVC radiation) that is output by a UVC bulb decreases the further the UVC rays travel. As UVC rays travel, its effectiveness on a virus twice as far away is only 25%. A UVC ray that can kill a virus in 1 second 6 inches away would take 4 seconds to kill when it 12 inches away. A virus 2 feet away would take 16 seconds to die. This phenomenon is called the Inverse-square law.
Residency time is the amount of time any particle remains within the UVC Chamber. Residency time is determined by taking the airspeed which is expressed as LFM (linear feet per minute) and dividing that by the length of the UVC Chamber. (There is a lot of complicated math that is beyond the scope of this article. However, I will list my references at the end of the article and you can research, multiply, and divide until your heart is content.)
The end product is UVC dosage. This is expressed in µJ/cm² (microjoules per square centimeter). So, the question is how much dosage does it take to kill COVID-19. There is no firm agreement on the exact dose. The current variety is considered a wimp in comparison to its cousins. Studies have shown that even at the highest level of COVID particles present it takes only 84.4 µJ/cm² to deactivate it.
The table below shows the results from various studies on different strains of SARS related viruses and the amount of UVC radiation to disable them.
Table: Summary of UV light studies on Coronaviruses
Coronavirus 7 J/m2 Walker 2007
Berne virus (Coronaviridae) 7 J/m2 Weiss 1986
Murine Coronavirus (MHV) 15 J/m2 Hirano 1978
Canine Coronavirus (CCV) 29 J/m2 Saknimit 1988
Murine Coronavirus (MHV) 29 J/m2 Saknimit 1988
SARS Coronavirus CoV-P9 40 J/m2 Duan 2003
Murine Coronavirus (MHV) 103 J/m2 Liu 2003
SARS Coronavirus (Hanoi) 134 J/m2 Kariwa 2004
SARS Coronavirus (Urbani) 241 J/m2 Darnell 2004
Average 67 J/m2
What to Look for when Buying a UVC Filtration System
In our opinion, some companies are putting out products that are not very effective. Products that rely only on the exposure from direct UVC rays and convection airflow will not sufficiently clean the air in the rooms they are placed.
The viruses and bacteria in the air do not come in direct contact with UVC rays long enough to really sanitize the room. Theoretically, if the room was closed long enough and received no extra infectious material would certainly be cleansed.
That’s not how our world works. We live, play, work, and learn in the real world in real-time. Things are happening, people come and go. People breathe, sneeze, and cough. Buy UVGI filtration that actively cleans the air. While some sanitization happens through direct UVC rays and convection, there is not enough in most cases for it to be considered effective.
We have seen products that have a 10-watt UVC bulb with no fans or vents for convection airflow. These units produce 4 watts of UVC radiation and are effective for about 6 feet. Some of these products sell for over $1200.00 and do very little to clean the air. Ask what UVC dosage their product provides! More than likely the salesperson has no idea. The principle of air changes per hour in still very important. 2 ACH of effective UA-UVC (upper air UVC) is a good deterrent against viral particles.
Continuing Product Development
LakeAir is dedicated to providing the best clean air options for its customers. We will continue to produce high quality all steel constructed air purifiers. We are working on new products to provide affordable air filtration for homes and businesses. If you would like more information on any of our products, contact us by phone or email.
Sources
https://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradiation
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4702654/
https://www.orf.od.nih.gov/TechnicalResources/Bioenvironmental/Documents/Applicationsofultravioletgermicidalirradiationdisinfectioninhealthcarefacilities_508.pdf
https://in.dental-tribune.com/news/how-to-use-ultraviolet-light-uvc-to-fight-covid-19-effectively-in-dental-clinics-dr-ajay-bajaj/
https://www.ashrae.org/file%20library/technical%20resources/covid-19/i-p_a19_ch62_uvairandsurfacetreatment.pdf
https://en.wikipedia.org/wiki/Inverse-square_law#:~:text=The%20intensity%20(or%20illuminance%20or,only%20one%2Dquarter%20the%20energy