The Science Behind UV Disinfection

What is Ultraviolet Germicidal Irradiation (UVGI)?

Health concerns such as canine influenza, kennel (canine) cough, parvovirus, feline calicivirus, as well as illnesses that impact human animal care providers, are a real concern and a constant threat to the animals in your care, your staff, your business and reputation. Ultraviolet germicidal irradiation (UVGI), also commonly referred to simply as UV, can help prevent the spread of a variety of diseases that can impact an animal facility. But what is UV? Why and how does it work? And why should you invest in UV? The following offers a brief overview of the science behind UV, including an introduction to UV’s remarkable history.

What is UV light disinfection?

Ultraviolet germicidal irradiation or UVGI is a term used by federal agencies such OSHA, NIOSH, and the CDC when referring to UV-C. Scientists divide the ultraviolet spectrum into three bands (better known as UV rays):

  • UV-A causes wrinkling, sagging, and premature aging of skin.

  • UV-B causes sun burns and skin cancer.

  • UV-C is germicidal and lethal to microorganisms.

This germicidal UV is a proven, professional level means of disinfection for hospitals and other high-risk environments like animal care facilities where respiratory infections are easily spread and maintaining sanitary air circulation and surface areas is critical. UV has the ability to kill the microbes that are known to cause:

Canine influenza  |  Canine parvovirus  |  Feline calicivirus  |  Kennel cough (canine cough)  |  Canine distemper  |  Canine coronavirus  |  Zoonotic diseases

UV also provides energy savings benefits. Aerapy Animal Health’s UV for HVAC systems will also naturally and safely break down and clear away the mold and biofilm that, over time, build up on HVAC coils, plenums, drain pans, and ducts. Clean coils can lower your energy cost by reducing pressure drop and improve heat transfer, increasing cooling capacity.

How are germs spread?


For the spread of airborne viruses and bacteria there are different transmission routes, including via droplets and via droplet nuclei. A standard droplet is generally greater than 10 µm (microns). At this size, droplets won’t stay suspended in the air, typically traveling 3–6 feet before landing on a surface. These are disinfected using surface cleaners and can be followed up with Aerapy Animal Health’s surface UV disinfection units for greater than a 99.99% kill rate of tested virus and bacterial pathogens. To learn more about the tested viruses, including how they cover the spectrum of hardiness in the environment and satisfy six key factors to meet all combinations for viruses, visit our Research & Studies page.

Droplet Nuclei

Droplet nuclei, however, are much smaller than droplets—less than 5 microns in diameter—and they can stay in the air traveling on dust particles for extended periods of time. To prevent the spread of droplet nuclei, special procedures need to be put into place for air handling and ventilation which is why UV is a top solution.

Pathogens that may cause an animal to become extremely sick and spread infection throughout your facility can involve pathogens that are under 5 microns in size. For example, the following pathogens are all under 3 microns in size: canine influenza (0.101); canine parvovirus (0.092); Bordetella bronchiseptica or canine cough (0.0364); canine calicivirus (0.0345); feline calicivirus (0.0345); canine distemper virus (0.1100); methicillin resistant Staphylococcus aureus or MRSA (0.03-1.0); animal dander (2.5).

How does UV disinfection work?

How does UV help stop the spread of germs? Simply put, UV works as a mutagen to bacteria, viruses, and other microorganisms on a cellular level, penetrating the cell wall. This disrupts the microorganism’s DNA (deoxyribonucleic acid), breaking the carbon bond, which causes the death of the cell and/or renders it helpless.

Illustration showing how UV light breaks the microorganism's DNA carbon bond causing cell death

How to choose the right UV light for sanitizing?

There’s no one size fits all.

While we’ve given you the quick explanation of the science, there is also no “one size fits all” solution when choosing UV air and surface disinfection systems. As stated in “Ultraviolet Germicidal Irradiation Current Best Practices” published by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers):

“A UVGI system design today relies on performance data from lamp manufacturers, the experience of system designers, and the recommendations of UVGI equipment manufacturers.” (ASHRAE Journal, August 2008).

A big part of that experience is addressing the specific pathogens of concern in a particular environment. That is, an animal facility may have different or additional concerns than a human healthcare environment. While zoonotic pathogens, those transmitted between animals and humans, are of concern in virtually all environments, the array of zoonotic pathogens of concern may be greater in animal care environments, along with animal and human pathogens.

Proprietary UV Analysis

Aerapy Animal Health’s proprietary UV analysis software and proprietary sizing method are specifically adapted for zoonotic pathogens and may result in different design parameters (e.g., lamp power levels, filter size, airflows, etc.) than system sizing methods used for human indoor environments. By addressing the specific pathogens of concern in any animal facility, the Aerapy Animal Health design process can ensure that the highest practical removal rates can be achieved and that the risk of zoonotic, animal, and human disease transmission can thereby be minimized. Test results from an independent laboratory using strict test methods, show that Aerapy Animal Health UV systems killed more than 99.9% of tested virus and bacterial pathogens. Learn more on our Research & Studies page.

The History of UV Sanitization

For more than a century, UV has been a known mutagen at the cellular level and has long been utilized for infection control in human healthcare and government facilities. As early as 1845, it was known that microorganisms respond to light and, in 1878, Arthur Downes and Thomas P. Blunt published a paper describing the sterilization of bacteria exposed to short-wavelength light. A quarter of a century later, in 1903, Niels Finsen was awarded the Nobel Prize in Physiology or Medicine for his use against lupulus vulgaris or tuberculosis of the skin. Despite UV’s considerable history, many animal care professionals are not familiar with the trajectory of UV and how it has been utilized for infection control.

The 1930s marked milestones in the advancement of the use of UV for infection control as William F. Wells presented the concept of the spread of airborne infection by droplet nuclei and demonstrated the ability of UV to prevent the spread. Additional details on the pioneering work of Wells, including his use of upper room UV to dramatically reduce the incidence of measles, is well-documented in the highly recommended The History of Ultraviolet Germicidal Irradiation for Air Disinfection by Nicholas G. Reed published by the US National Library of Medicine National Institutes of Health.