June 20, 2021
Last Updated On:
July 12, 2022

UV-C/UVGI: What You Need To Know

UV-C Technology, Virus Killing Methods, & Indoor Air Disinfection.

Last Updated On:
July 12, 2022

The air we breathe contains large numbers of harmful particles like bacteria, viruses, and molds. 

While we have limited control over outdoor air quality, we can control indoor air quality with heating, ventilation, and air conditioning (HVAC) units and air purifier systems.  

Standard air ventilation and filtration systems use multiple air filters to clean the air while circulating through the indoor spaces. Each filter uses a different method for trapping certain particles. In addition, filters like True HEPA filters and activated carbon are designed for capturing particles of a specific size and type. 

Consider UV-C air filtration technology through Sanalife to capture microorganisms like bacteria, viruses, mildew, and airborne mold spores.

What is UV-C?

You may have heard of ultraviolet (UV) light through sun exposure. In general, UV light is electromagnetic radiation that is present in sunlight. It makes up 10% of the total light that the sun generates. This electromagnetic energy has shorter wavelengths than visible light but longer wavelengths than x-rays. 

UV-C stands for ultraviolet-C, and it is one of the classified subbands of ultraviolet light, measured by its light wavelengths (measured in nanometres). UV light, which encompasses three subbands, UV-C, UV-B, and UV-A, measures the lower or shorter wavelength spectrum. UV lights range from 10nm to 400nm. Comparatively, visible light wavelengths range from 400nm to 700nm. Above 700nm is infrared light.

All light that measures fewer than 290nm wavelengths is said to have germicidal properties. So while the sun gives off this type of light (UV-C and UV-B light), it is, for the most part, blocked by the Earth's atmospheric ozone. Luckily, UV light can be reproduced for disinfectant purposes. 

UVGI Wall Light Fixture Air Purifier

UV Light as a Disinfectant

Scientists have known about the disinfectant properties of ultraviolet light for over 140 years. Downes and Blunt initially discovered the antibacterial effects of UV sunlight in 1877. Soon after, scientists were able to prove that portions of UV can be used to destroy microorganisms. 

Once this was realized, scientists found a way to replicate UV wavelengths for disinfectant purposes. The first UV quartz lamp was invented in 1904, and this led to a germicidal lamp that produced UV-C wavelengths (200 nm to 280nm) with disinfectant properties

So how can UV be a disinfectant?

Disinfectants kill bacteria and viruses. UV does it by damaging the cells' DNA or RNA, killing the cells. Once a bacteria or virus particle is exposed to UV light, its genetic material is modified. When you think about UV light as radiation, then you can understand how this harmful radiation, when unobstructed by the Earth's ozone, can kill cells. 

When you get into the nitty-gritty of how this breakdown occurs, think of how radiation kills cells. Through photochemical reactions, the radiation energy hits a cell and triggers chemically-induced molecular lesions. This trigger signals a mutation or cell death so that the microbes become inactive (dead and unable to reproduce). 

In DNA, the trigger causes thymine and cytosine dimers (thymine and cytosine are two of four chemical bases in DNA), and in RNA, uracil dimers are formed. Dimers are kind of like blockages, and as little as one dimer can be lethal to a virus cell. Dimers are most efficiently formed in a virus particle when it is hit with UV-C. 

So, scientifically, when targeting UV-C radiation energy at a virus particle, it will be able to penetrate to the DNA or the RNA of that molecule and cause it to become lethal. 

According to the Centers for Disease Control (CDC): "UV can kill all bacteria, including drug-resistant bacteria because UV light is actually attacking the DNA and RNA of microbes. While the amount of UV needed to kill a microbe may vary as there is a relationship between the size of DNA molecules and the effect of UV radiation, there have been no reports of microbes demonstrating an ability to build an immunity to light-based methods."

This makes for a very effective disinfectant!

Static UV-C Disinfecting Light Fixtures

What is Ultraviolet Germicidal Irradiation (UVGI)?

Because UV-C is such a powerful antibacterial and antiviral energy, it is no surprise that we have made efforts to reproduce this light as a method for cleaning. 

The use of UV-C as a method for killing viruses and bacterias is called UVGI. While a fancy term, ultraviolet germicidal irradiation (UVGI) is simply the method of using short-wavelength UV-C light to disinfect and kill microorganisms and pathogens. UVGI is used for disinfecting surfaces, air, and water and has been recommended to isolate diseases and as a bio-defense system in military and government buildings

UVGI's effectiveness depends on how long the microorganisms are exposed to UV light. However, the light intensity and wavelength can also kill the microorganism faster. 

ActivePure The Smarter Choice

How Does UV-C/UVGI Technology Work for Air Filtration?

When we talk about using UV-C technology for air filtration, we realize that cleaning or filtering the air is called UVGI. UV-C is one of the components of the cleaning mechanism. 

UVGI is the specific method of sterilizing the air, and it uses UV-C to do so. UV-C-based air purifying technology works as one of several filters that clean the air that passes through it. The machine will force air through the filter (often after the air goes through particle filters like HEPA) and is pushed through the chamber holding a UV-C light emitter. 

Once the air is forced into the unit, the air must settle for a short time in the UV-C chamber. 

The emitter is usually phosphor or quarts and can be blue-tinted or not visible to the human eye. Common residential air purifier units will use mercury lamps with 254 nm wavelength UV-C. 

UV-C light air purifiers are rarely sold as stand-alone products, and they are typically used in combination with HEPA filters because they cannot trap particles. This is most likely because UV-C light cannot trap or remove allergens, chemical fumes, pet dander, cigarette smoke, molds, dust, and volatile organic compounds (VOCs).

Upper-Room UVGI Disinfection System Diagram (Source: Engineered Systems Magazine)

The Effectiveness of UV-C Air Purifiers

UV air purifiers are generally effective at deactivating mold and bacteria and some amount of viruses. However, they have not been as effective at reducing bacterial spores and mold spores. Higher levels and a longer exposure time could destroy bacterial and mold spores, but these are usually at levels higher than stand-alone units. 

The bulb intensity and the duration of the air being held in the chamber can improve the filter's effectiveness. Additional factors of its effectiveness include:

  • Whether the airflow cools the light
  • The material of the emitter bulb
  • The dosage of light required
  • How long the pollutant is exposed
  • Whether the contaminants come into contact with the UV light

The terms sterilization, disinfection, and decontamination are all used interchangeably when discussing UVGI's effectiveness for cleaning, but it's important to note them here

  • Sterilization: This is the process of destroying or eliminating microbial life through physical or chemical methods. 
  • Disinfection: The process of eliminating many or all pathogenic microorganisms, usually on inanimate objects. 
  • Decontamination: To make an object or area safe by neutralizing, removing, or destroying harmful substances. Decontamination results after sterilization and disinfection. 

UV-C does not perform full sterilization or full decontamination, but it can disinfect the air of many airborne pathogens, primarily microorganisms. UV-C light air filtration would be one of the most effective methods for disinfecting certain air particulates during the COVID-19 pandemic.  

One of the biggest challenges with UV-C is that it emits ozone. It is also an oxidizer and toxic to living things. Therefore, when used in an air purifier system, the ozone needs to be properly addressed. Caution should be taken to limit the exposure of ozone in elevated levels to plants, pets, and people. 

UV PCO Based True HEPA Air Purifier

Using Photocatalytic UV-C (PCO Technology) Air Purifier Systems

UV-C light for disinfection is not perfect. However, the ability to kill virus and bacteria molecules is enhanced when emitted through titanium dioxide. Additionally, the FDA recommended UV-C light to destroy the SARS-Coronavirus's outer layer and potentially inactivate the SARS-CoV-2 virus, the virus that causes COVID-19.

UV-C lighting can also be enhanced by other means. Photocatalytic UV-C is one way. UV-C light activated by a titanium dioxide catalyst can result in the removal of viruses & bacteria. Air purifier systems that use titanium dioxide do so through photocatalytic oxidation air purification. The titanium dioxide is the photocatalyst and, once exposed to light; it mediates a chemical reaction on its surface. This chemical reaction is then used to break down pollutants. 

This mechanism works by exciting titanium dioxide, which then degrades the virus and bacteria cell walls, killing them and removing them from the air. This technology is called photocatalytic UV-C because of titanium dioxide's properties as a photocatalyst

By transforming harmful viruses and bacteria into non-harmful molecules, PCO technology can remove harmful pathogens with greater efficiency.

Consider getting UV-C or PCO technology to mitigate virus spread in your business. With a smart system that has multiple layers of filtration, you may find that your air is cleaner, your patrons are happier, and you are doing as much as you can to protect your business while it reopens during the COVID-19 pandemic. 

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