UV Technology for a Cleaner, Safer Indoor World.

UV-C 101

Answers about germicidal UV-C lighting.

Below are questions and answers about UV-C basics, its germicidal benefits, its safety and regulation, and its use against the new coronavirus:


Q: What is UV-C?
A: UV-C is an electromagnetic frequencies emanating from the sun. Its frequency waveforms provide unique properties are unique to its wavelength. The “C” refers to the “C” frequency of the electromagnetic ultraviolet or UV family which includes germicidal effects.

Q: How is UV-C light made?
A: Low-pressure mercury vapor, germicidal lamps were developed back in the early 1930’s. Today’s UV-C lamps use the germicidal wavelength of 253.7nm for air and water disinfection. To synthesize the UV-C frequency, a glass fixture tube is filled with argon at far below atmospheric pressure. A small amount of mercury is added so that when it is energized, a glowing plasma of electrons pass through the mercury vapor. As they strike mercury atoms, mercury electrons are released at the 253.7nm frequency – mercury’s spectral line – and emit UV-C energy.

Q: How long has UV-C been used for sterilization?
A: Since the finding in 1878, artificially produced UV-C has become a staple method of sterilization – one used in hospitals, airplanes, offices, and factories every day. Crucially, it’s also fundamental to the process of sanitizing drinking water; some parasites are resistant to chemical disinfectants such as chlorine, so it provides a failsafe.

The application of UVGI to disinfection has been an accepted practice since the mid-20th century. It has been used primarily in medical sanitation and sterile work facilities. Increasingly, it has been employed to sterilize drinking and wastewater since the holding facilities are enclosed and can be circulated to ensure a higher exposure to the UV. UVGI has found renewed application in air purifiers.

In 1878, Arthur Downes and Thomas P. Blunt published a paper describing the sterilization of bacteria exposed to short-wavelength light. UV has been a known mutagen at the cellular level for over 100 years. The 1903 Nobel Prize for Medicine was awarded to Niels Finsen for his use of UV against lupus vulgaris, tuberculosis of the skin.

Using UV light for disinfection of drinking water dates back to 1910 in Marseille, France. The prototype plant was shut down after a short time due to poor reliability. In 1955, UV water treatment systems were applied in Austria and Switzerland; by 1985 about 1,500 plants were employed in Europe. In 1998 it was discovered that protozoa such as cryptosporidium and giardia were more vulnerable to UV light than previously thought. This opened the way to wide-scale use of UV water treatment in North America. By 2001, over 6,000 UV water treatment plants were operating in Europe.

Over time, UV costs have declined as researchers develop and use new UV methods to disinfect water and wastewater. Currently, several countries have developed regulations that allow systems to disinfect their drinking water supplies with UV light.


Q: How does UVC affect germs?
A: Microorganisms are simple organic structures that easily absorb UV-C light, destroying it through photo-disassociation. A microbe’s DNA suffers irreparable damage almost instantly by UV-C weakening its molecular bonds. This ultimately causes the cells to die and/or become unable to replicate. Continuous exposure to UV-C causes accelerates the degradation.

Q: BluWav ASTRA UV-C germicidal lamps cause microbe inactivation. What is that?
A: For mold and bacteria, doses of UV-C energy may not cause immediate cell death but the microbe could be “inactivated” meaning while some biological activity may still exist, cell replication is no longer possible. Simply, the subject microbe cannot multiply, rendering it harmless! What’s more, small doses of UV-C over time have been shown to hasten cell death. As viral particles are not a life form, we depend solely on inactivation to rid ourselves of their impending harm.

Q: If UV-C energy is invisible, what is the violet blue light seen?
A: About 90% of the energy generated by a UV-C lamp is UVC energy. The remainder of the energy is visible light (violet blue hue) with a small amount of infrared (heat). Given the light brightness from UV-C lamps is less than 5% of the total UV-C energy, it is easy to deduce the high amount of t of visible light gives one an idea of the amount of UVC energy a lamp produces.

Q: Can BluWav ASTRA UV-C germicidal lamps save energy and energy costs associated with HVAC systems?
A: Yes, in literally thousands of controlled tests, organic materials build-up on coils was removed with UV-C to provide two eventual results: 1. the pressure drop across a coil declines to increase air flow. 2. the leaving air wet-bulb temperature differential increases. Energy savings are therefore through increased heat absorption (transfer), reduced air horsepower (or increased air volume) and/or reduced run time, including at a condenser. These reductions and increases always manifest themselves in some form of energy saving work.

Q: How does UV-C work with air filters to remove microorganisms?
A: HVAC filters can reduce the total number of microbes in the air by catching them in its surface material. To actually kill the microbes, filters can also be paired with UV-C lamps in a “catch and kill” approach. With proper positioning to the filter, UV-C can kill and/or degrade what the filter has caught. UV-C, not filters, is required to remove microbial growth on the surfaces of drain pans, plenum’s and ductwork.  


Q: Can UV-C light be used to kill the new coronavirus?
A: In short, yes. Because UV-C can effectively inactivate the new coronavirus without using chemicals, UVC light is an attractive option for disinfection. Special lamps that emit UV-C light are typically used for this purpose. The optimal length of exposure, wavelength, and dose of UVC light needed for killing the new coronavirus is yet to be determined.

Q: Do UV-C lamps inactivate the SARS-CoV-2 coronavirus?
A: (FDA) UVC radiation is a known disinfectant for air, water, and nonporous surfaces. UVC radiation has effectively been used for decades to reduce the spread of bacteria, such as tuberculosis. For this reason, UV-C lamps are often called “germicidal” lamps.

UVC radiation has been shown to destroy the outer protein coating of the SARS-Coronavirus, which is a different virus from the current SARS-CoV-2 virus. The destruction ultimately leads to inactivation of the virus.  efficiently and safely inactivates airborne human coronaviruses. UV-C radiation may also be effective in inactivating the SARS-CoV-2 virus, which is the virus that causes the Coronavirus Disease 2019 (COVID-19). Currently there is limited published data about the wavelength, dose, and duration of UV-C radiation required to inactivate the SARS-CoV-2 virus.

Q: Who is advocating UV Disinfection for COVID-19?
A: The International Ultraviolet Association (IUVA) believes that UV disinfection technologies can play a role in a multiple barrier approach to reducing the transmission of the virus causing COVID-19, SARS-CoV-2, based on current disinfection data and empirical evidence. UV-C is a known disinfectant for air, water and surfaces that can help to mitigate the risk of acquiring an infection in contact with the COVID-19 virus when applied correctly.

Q: Is UV-C being used to specifically fight COVID-19?
A: A concentrated form of UV-C is now on the front line in the fight against COVID-19. In China, whole buses are being lit up by the ghostly blue light each night, while squat, UVC-emitting robots have been cleaning floors in hospitals. Banks have even been using the light to disinfect their money.

Q: If sunlight contains UV, does it kill Covid-19? 
A: Sunlight contains three types of UV. First there is UV-A, which makes up the vast majority of the ultraviolet radiation reaching the Earth’s surface. It’s capable of penetrating deep into the skin and is thought to be responsible for up to 80% of skin ageing, from wrinkles to age spots.

Next there’s UV-B, which can damage the DNA in our skin, leading to sunburn and eventually skin cancer (recently scientists have discovered that UV-A can also do this). Both are reasonably well known, and can be blocked out by most good sun creams.

The third type is UV-C. This relatively obscure part of the spectrum consists of a shorter, more energetic wavelength of light that is particularly good at destroying genetic material – whether in humans or viral particles. Luckily, most of us are unlikely to have ever encountered any. That’s because it’s filtered out by ozone in the atmosphere long before it reaches our fragile skin.


Q: Is UV-C harmful?
A: We are exposed to many frequencies of UV light while outdoors on sunny days. Many wear sunscreen knowing that too much exposure to UV light can be harmful causing conditions including skin cancer and cataracts. This is primarily is caused by UV-B, a narrower more dangerous band of UV. Overexposure to UV-C can cause temporary skin redness and harsh eye irritation, but no permanent damage, skin cancer, or cataracts.

Q: Do UV-C lamps produce ozone?
A: No. UV-C does not produce ozone. Like the sun does outdoors, UV-C does an exceptionable job conditioning of the air. This is why UV-C lamps are used in air conditioning systems particularly in air handler units. They sanitize the air and disinfect the surfaces of filters, coils, heating cores, fan, dampers, humidifiers, and other components. All are designed to provide a specific function in the job of processing air for occupied spaces.

Q: Are UV-C disinfection lamps safe?
A: Like any disinfection system, UV-C lamps must be used properly to be safe. They all produce varying amounts of UV-C light in wavelengths of 200nm-280nm. This UV-C light is much “stronger” than normal sunlight, and can cause a severe sunburn-like reaction to your skin. The target tissue in the eye would be the cornea. The effect on the cornea is called photokeratitis, which is like a sunburn of the eye.

Q: Are all lamps that produce UV-C radiation the same?
A: (FDA) Not all UVC lamps are the same. Lamps may emit very specific UV-C wavelengths (like 254 nm or 222 nm), or they may emit a broad range of UV wavelengths. Some lamps also emit visible and infrared radiation. The wavelengths emitted by the lamp may affect the lamp’s effectiveness at inactivating a virus and may impact the health and safety risks associated with the lamp. Some lamps emit multiple types of wavelengths. There is some evidence that excimer lamps, with peak wavelength of 222-nm may cause less damage to the skin, eyes, and DNA than the 254 nm wavelength, but long-term safety data is lacking.

Q: Are BluWav ASTRA UV-C germicidal lamps UL listed?
A: Yes. For the safety of HVAC professionals and consumers alike, UVGI lamps like BluWav ASTRA UV-C germicidal lamps must be tested and Listed as UL/C-UL under Category Code ABQK (Accessories, Air Duct Mounted), UL Standards: 153, 1598 & 1995 respectively.

Q: What is the FDA’s role in the oversight of UV-C lamps?
A: (FDA) UV-C lamps are electronic products. The FDA regulates electronic products that emit radiation (both non-medical and medical products) through the Electronic Product Radiation Control Provisions, which were originally enacted as the Radiation Control for Health and Safety Act. Certain electronic products may also be regulated as medical devices. The FDA is responsible for regulating firms who manufacture, repackage, relabel, and/or import medical devices sold in the United States.

UV-C lamp manufacturers are responsible for compliance with all applicable regulatory requirements, including Title 21 Code of Federal Regulations (CFR) Parts 1000 through 1004, and section 1005.25 and, as applicable, 21 CFR Chapter I, Subchapter H. The radiological health regulations include reporting of Accidental Radiation Occurrences, notification to the FDA and customers of radiation safety defects, and designation of a U.S. agent for imported lamps. When a UV-C lamp is regulated only as an electronic product, there are currently no specific FDA performance standards that apply.
Ultraviolet lamps intended for medical purposes, such as products that disinfect other medical devices or irradiate part of the human body, that meet the definition of medical device under section 201(h) of the Federal Food, Drug, and Cosmetic Act also typically require FDA clearance, approval, or authorization prior to marketing.

Q: Does UL perform Ultraviolet (UV) testing and certification?
A: (UL) In the current global situation, questions surrounding sanitation, germicidal properties, and UV devices are more in focus than ever before. Safety considerations around the use of UV lighting and radiation are critical when so many new products are entering the markets of lighting, appliances, consumer products, healthcare and more.
UV-C radiation has sanitizing properties and has many uses in commercial, healthcare, and consumer settings. UV-C has germicidal benefits, depending on exposure dose (based on strength, proximity and time). However, there are serious risks to UV-C exposure, so safety precautions are essential. 

A critical term to keep in mind when discussing UV-C is containment, which refers to a set of design criteria in which people are not exposed to excessive UV-C but the germs are. You will see “containment” used throughout this site in reference to the design criteria. In consumer oriented germicidal devices containment is achieved by locating the UV-C source within the product enclosure. In contrast, germicidal devices intended for use by trained professionals in controlled settings may have exposed UV-C sources. With these designs, product and site safeguards and intended use are considerations for evaluation and certification.

These different approaches relate to higher risks of improper use (intentional or otherwise) by consumers who may not follow (or understand) safety warnings on the product or the packaging. In contrast, trained professionals are expected to follow safety instructions and use necessary protective equipment.

Q: How does UL view Nonmedical UV-C products?
A: (UL) The use of UV-C devices in schools, offices, hospitality/entertainment, food services, airports/transportation/car services and many other locations are a key focus for building owners, facilities managers and administrators alike.
Anyone involved with germicidal and disinfecting products should be interested in the safe use of UV-C devices related to lighting, HVAC, appliances and other product categories. From functional safety to predictive modeling and robotic technology, UL can help you navigate the use of UV-C in enclosed products, UVGI applications, open air technology and more. 


Q: Are BluWav ASTRA X14 UV-C lamps hard to install?
A: No. HVAC professionals will have no problem properly installing the lamps. Installation instructions are provided along with diagrams showing placement specifics and each step. ASTRA X14 UV-C lamps are designed to be installed in air handler units in less than an hour!

Q: Do BluWav ASTRA UV-C germicidal lamps need cleaning?
A: Periodic cleaning is usually not required for UV-C lamps. UV-C energy will typically degrade organic debris that might accumulate on the tube surface.

Q: Why is there more microbial activity inside an HVAC system today?
A: The reason there is more microbial activity inside an HVAC system today is due to the more advanced operating scheduling with newer thermostats. Time clock operation (A/C system shut down – to conserve energy) exacerbates microbial growth. During these 8 – 12 hour, and weekend shut-downs, higher surface and liquid temperatures are achieved. These warmer but still damp coils and drain pans are perfect microbial forums.

Nasa Based UV Light technology

NASA-Based UV-C sterilization technology to eliminate or reduce most microorganisms

What is UV-C or germicidal UV?

UV light is electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays. UV is categorized into several wavelength ranges, with short-wavelength UV (UV-C) considered “germicidal UV”. Wavelengths between about 200 nm and 300 nm are strongly absorbed by nucleic acids. The absorbed energy can result in defects including pyrimidine dimers. These dimers can prevent replication or can prevent the expression of necessary proteins, resulting in the death or inactivation of the organism. This process is similar to the effect of longer wavelengths (UV-B) producing sunburn in humans. Microorganisms have less protection against UV and cannot survive prolonged exposure to it.

UV-C light is weak at the Earth’s surface since the ozone layer of the atmosphere blocks it. UVGI devices can produce strong enough UV-C light in circulating air or water systems to make them inhospitable environments to microorganisms such as bacteria, viruses, molds, and other pathogens. UVGI can be coupled with a filtration system to sanitize air and water.

What is UVGI?

Ultraviolet germicidal irradiation (UVGI) is a disinfection method that uses short-wavelength ultraviolet (UV-C) light to kill or inactivate microorganisms by destroying nucleic acids and disrupting their DNA, leaving them unable to perform vital cellular functions. UVGI is used in a variety of applications, such as food, air, and water purification.

The application of UVGI to disinfection has been an accepted practice since the mid-20th century. It has been used primarily in medical sanitation and sterile work facilities. Increasingly, it has been employed to sterilize drinking and wastewater since the holding facilities are enclosed and can be circulated to ensure a higher exposure to the UV. UVGI has found renewed application in air purifiers.

A UVGI system is designed to expose environments such as water tanks, sealed rooms and forced air systems to germicidal UV. Exposure comes from germicidal lamps that emit germicidal UV at the correct wavelength, thus irradiating the environment. The forced flow of air or water through this environment ensures exposure.

The effectiveness of germicidal UV depends on the length of time a microorganism is exposed to UV, the intensity and wavelength of the UV radiation, the presence of particles that can protect the microorganisms from UV, and a microorganism’s ability to withstand UV during its exposure.

In many systems, redundancy in exposing microorganisms to UV is achieved by circulating the air or water repeatedly. This ensures multiple passes so that the UV is effective against the highest number of microorganisms and will irradiate resistant microorganisms more than once to break them down.

How does UV-C inactivate microorganisms?

The degree of inactivation by ultraviolet radiation is directly related to the UV dose applied to the water. The dosage, a product of UV light intensity and exposure time, is usually measured in microjoules per square centimeter, or equivalently as microwatt seconds per square centimeter (μW·s/cm2). Dosages for a 90% kill of most bacteria and viruses range between 2,000 and 8,000 μW·s/cm2. Larger parasites such as cryptosporidium require a lower dose for inactivation. As a result, the U.S. Environmental Protection Agency has accepted UV disinfection as a method for drinking water plants to obtain cryptosporidium, giardia or virus inactivation credits. For example, for a 90% reduction of cryptosporidium, a minimum dose of 2,500 μW·s/cm2 is required based on the U.S. EPA UV Guidance Manual published in 2006.

UVGI can be used to disinfect air with prolonged exposure. In the 1930s and 40s, an experiment in public schools in Philadelphia showed that upper-room ultraviolet fixtures could significantly reduce the transmission of measles among students. In 2020, UVGI is again being researched as a possible countermeasure against the COVID-19 pandemic.

Disinfection is a function of UV intensity and time. For this reason, it is in theory not as effective on moving air, or when the lamp is perpendicular to the flow, as exposure times are dramatically reduced. However, numerous professional and scientific publications have indicated that the overall effectiveness of UVGI actually increases when used in conjunction with fans and HVAC ventilation, which facilitate whole-room circulation that exposes more air to the UV source. Air purification UVGI systems can be free-standing units with shielded UV lamps that use a fan to force air past the UV light. Other systems are installed in forced air systems so that the circulation for the premises moves microorganisms past the lamps. Key to this form of sterilization is placement of the UV lamps and a good filtration system to remove the dead microorganisms. For example, forced air systems by design impede line-of-sight, thus creating areas of the environment that will be shaded from the UV light. However, a UV lamp placed at the coils and drain pans of cooling systems will keep microorganisms from forming in these naturally damp places.
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