FAQs: Frequently Asked Questions on UV Light, UVC Light Appliances and Dual-Mode Room Disinfection Applications of UVC Light and Ozone
- Q: What is UV light?
A: Ultraviolet (UV) light is short wavelength (10-400 nanometers) light (invisible to the human eye) that is given off from the sun as well from as man-made sources, including arc welders, tanning beds and UV disinfection lamps. A nanometer (nm) is a billionth of a meter. There are three main classes of UV light: UVA, UVB and UVC. UVA (315–400nm) and UVB (280–315) light causes sunburns and premature skin aging, and exposure to both is associated with the development of skin cancer due to the ability to damage DNA. UVC light, which has the shortest wavelength of all three types (100–280nm), is the most harmful, but fortunately does not reach the Earth’s surface from the sun because our atmosphere absorbs it. Man-made UVC light is considered germicidal UV and is used for disinfection because of its ability to destroy genetic material, both DNA and RNA. - Q: What are some examples of disinfection using UVC light?
A: Disinfection using UVC light is common in wastewater treatment applications and is finding an increased usage in municipal drinking water treatment. Many bottlers of spring water use UVC disinfection equipment to sterilize their drinking water. UVC light is used in several food processes to kill unwanted microorganisms. UVC light can be used to pasteurize fruit juices by flowing the juice over a high-intensity UVC light source. UVC light is also safely used when enclosed within HVAC units to disinfect the air and kill mold spores as the air passes through the HVAC unit. - Q: Are exposed UVC disinfection lights safe to use with people or pets in the room?
A: NO! Exposed UVC lights cannot be used near people or pets! Our featured UVC disinfection appliances come with different combinations of safety features such as time-delayed start, remote controls, run-time timers, and/or motion sensors to prevent operation with people or pets in the room. - Q: What about use of UVC light with plants in the room?
A: UVC light destroys DNA and thereby kills organisms. Plants must also be removed from the room before treating with UVC light. - Q: What is ozone and how is it produced or destroyed by UV light?
A: Most free oxygen in the air at ground level is diatomic, that is, two oxygen atoms bound together in an O2 molecule. UVC light at wavelengths less than 240nm will break the bonds of diatomic oxygen, freeing up atomic oxygen (O) to combine with diatomic oxygen molecules (O2) to form ozone (a tri-atomic oxygen molecule O3). UV light will also be absorbed and by ozone and break ozone back down into atomic oxygen (O) and diatomic oxygen (O2) at wavelengths from about 200nm to 315nm (UVB/UVC). The ozone layer in the upper atmosphere is produced by solar UV light but also does a great job filtering solar UV wavelengths from about 100 – 315 nm. Onging ozone production and destruction by sunlight in the upper atmosphere are balanced, resulting in a relatively stable protective layer of ozone. This ozone layer is important as UVB and UVC are the harmful wavelengths of UV light that cause sunburn and DNA damage in living tissues. - Q: Can ozone be produced from manmade UV light sources?
- A: Ozone can be produced by manmade UVC light sources generating wavelengths less than 240nm. Optimum ozone generation occurs at approximately 180nm.
- Q: Do UVC light appliances also produce ozone? Is this dual-mode disinfection a benefit or is it harmful to humans?
- A: Many UVC light appliances are dual-band, that is, they are tuned to produce UVC light in the germicidal UVC range but they also produce light at approximately 180nm, which is optimum for ozone production. This rsults in a dual-mode disinfection where the ozone permeates the room during treatmemt and reaches areas where the UVC light may not directly reach, providing additional whole-room disinfection coverage. Ozone is an irritant to the respiratory tract, it has a distinct smell and must be allowed to dissipate for approximatley 45 minutes after whole-room treatment. Increased ventilation nay be helpful.
- Q: How do the germicidal mechanisms with ozone happen?
A: As a biocide, ozone works similarly to chlorine (another oxidant) and is used in a similar manner. Ozone disinfects by directly oxidizing and destroying the microorganism’s cell wall, causing cellular components to leak outside the cell. This causes protoplasmic destruction of the cell, damaging constituents of the nucleic acids, and breaks the carbon–nitrogen bonds, which leads to depolymerization. During the process, ozone splits into oxygen and an ozone atom, which is lost during the reaction with the microorganism’s cell fluids, O3 -> O2 + (O). Ozone destroys many viruses by diffusing through the protein coat into the nucleic acid core, where it damages viral RNA. At higher concentrations, ozone destroys the virus’ exterior protein shell so that DNA or RNA structures are affected. It is believed that also ozone destroys fungi and mold by diffusing through the fungalwall and into the cytoplasm, disrupting the organelles that direct cell function. Ozone generators are frequently used for pool and drinking water disinfection, as well as on meats and produce. Ozone acts to kill bacteria, viruses, and mold, and then safely dissipates leaving the food product, water, or surrounding air sterile. - Q: What is Far-UV light?
A: Far-UV (FUV) or Far-UVC light is a less-commonly discussed classification of UV light contained within the UVC range of 100–280nm, but is only comprised of the wavelengths between 122nm and 200nm. Some research indicates this class of UV light cannot actually penetrate the outer layer of the skin or the eye, but still exhibits germicidal properties on bacteria and viruses. The hope is that FUV light sources will be able to be used to continuously disinfect while people are in the room. A year-long animal study is underway to determine safety. The FDA would have to approve such a device for safe use around people.