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How Efficient Are UVGI Systems?

On a recent trip to the supermarket, I was amazed to see a robot making its way down the aisle. The robot, lovingly nicknamed Waldo, even had a surgical mask on in compliance with indoor mask regulations. As Waldo glided across the store, it stopped to meticulously scrub surfaces. With each new stop, a blue light beneath Waldo’s carriage illuminated the cleaned surface. Waldo’s mission was simple: to clean and disinfect. Never in my years of professional experience did I expect to see Jetsons’ technology in real life and here it was right in front of my eyes.

Today, robots are used in hospital settings to assist healthcare workers with many different tasks. We see robots performing surgery, delivering supplies to patient care areas, assembling instrument sets in sterile processing, and disinfecting critical areas as part of the environmental service team. In particular, disinfecting robotic tools have become extremely popular during the COVID-19 pandemic, revolutionizing how rooms are cleaned. But how effective are these devices and how do they work?

For veteran sterile processing professionals like myself, it is very easy to understand how a steam sterilizer renders a medical device sterile and ready for use. With proper temperature, humidity, and time settings, the process is successful and by feeling the heat the devices radiate after, we know that the process potentially worked. But ultraviolet germicidal irradiation (UVGI) operates very differently and relies on a spectrum of lights. This concept is not a new science. In 1845, two renowned scientists named Arthur Downes and T.P. Blunt discovered that exposing test tubes to sunlight prevents microbial growth.1 In the same experiment, they also concluded that keeping test tubes exposed to light keeps the test tubes free of bacteria. Since this discovery, ultraviolet disinfection technology has evolved, and today it plays a major role in our healthcare system and throughout hospital settings.

How is ultraviolet germicidal radiation used?
During the COVID-19 pandemic, we saw an increase in demand for surface disinfectors. Ultraviolet germicidal irradiation became the ideal solution to combat the virus because it removed microorganisms from objects and even entire rooms. Ultraviolet germicidal irradiation emits an invisible light which is shorter in wavelength than conventional light. Its spectrum consists of three parts: UV-B from 280–315 nm; UV-A from 315–400 nm, and UVC from 200–280 nm, which is closest to visible light. Employing UV-C radiation with a germicidal process has been found to be more reliable in destroying microorganisms than UV-B and UV-A radiation. 

This technology had been already in use to perform terminal disinfection of operating rooms and other critical hospital areas, like the ICU and the emergency department. Many hospitals have even established UV disinfection in SPD decontamination and preparation areas.

How does ultraviolet germicidal irradiation work?
When a surface is exposed to UV light at certain wavelengths, electromagnetic radiation modifies the genetic composition of microorganisms found on the surface and inhibits their ability to reproduce. The maximum bactericidal potential occurs at 240–280 nm. Ultraviolet germicidal irradiation systems are often used to disinfect air, water, and different kinds of surfaces. Prior to the COVID-19 pandemic, UV air disinfection systems were not well known. But as the need to disinfect airborne particles became necessary, upper-room UVGI systems became more popular. Upper-room UVGI systems are installed in ventilation systems to disinfect the air that flows in the room with UV energy. Factors such as distance, duration of the light, and exposure all influence the effectiveness of UV disinfection.

  • Distance: The effectiveness of UV disinfection depends on how far away the surface to be disinfected is from the light. If we compare it with a flashlight, the further one points the light to illuminate an area with a flashlight, the less intense the light and the darker the area. When relating this concept to UV disinfection, the closer the surface is to the rays of the light, the more effective the disinfection process and the greater the destruction of microorganisms.
  • Duration: The duration of the UV disinfection cycle is determined by several factors. The wattage of bulbs utilized in the UV disinfection system directly impacts how long the object needs to be exposed to the disinfection process, which in turn impacts the distance the object needs to be from the light. To help us understand this, let’s look at the example of a light bulb in a regular lamp. If we replace a 60-watt light bulb with a 125-watt one, we immediately notice a difference in brightness. The user must understand the intended operation and design of the equipment before purchasing. Carefully read the instructions for use to ensure the equipment meets the specification needed.
  • Exposure: Similar to the SPD sterilization process, all items need to be directly exposed to UV light to ensure efficacy of the UVGI system. Most manufacturers of UVGI systems require several units to be used in one room to ensure all surfaces in the room are exposed, as shadows or microshadows can limit the efficacy of the UVGI system. The germicidal effectiveness of the UVGI is directly affected by organic matter. In other words, all surfaces must be cleaned and free of debris, soil, and bodily fluids before exposing the room to UVGI disinfection.

Are UVGI systems essential in healthcare?
The use of UVGI systems in healthcare settings is not limited to surface disinfection. Throughout the COVID-19 pandemic, UV disinfection proved to be an effective way to meet high demand for equipment disinfection. Hospitals used UVGI systems to disinfect N95 respirators and, in some cases, disposable personal protective equipment, allowing healthcare workers to continue to provide care to patients.

But what about today? Do we still need UVGI systems in healthcare facilities? Advancements in technology and the need to rapidly communicate with other healthcare providers have increased the number of handheld devices in hospital settings. This includes cell phones, tablets, and other mobile devices that are often used to connect patients, doctors, and the hospital. According to a ScienceDirect article about microbial contamination of mobile phones, “72.6% of mobile phones revealed positive growth of one or more microorganisms. One hundred three mobile phones (39.8%) were contaminated with one microbe, while eighty-five (32.8%) were contaminated with more than one organism.”2 Microorganisms like Coagulase Negative Staphylococci (CoNS), methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Bacillus subtilis were found in some of the mobile devices tested.2 In fact, controlling cross-contamination from mobile devices used by healthcare workers has become the infection control practitioner’s worst nightmare.

A UVGI system is an efficient option for disinfection, as it can help expedite the process and prevent cross-contamination. Some UVGI systems can be transported to the end user’s location, such as the nursing patient areas, and all devices can be disinfected in as little as 55 seconds to achieve a 99.9% disinfection.

The threat of new viruses and antimicrobial-resistant microorganisms has meant finding new solutions for effective and rapid disinfection. UVGI systems and its many uses to treat surfaces, air, water, mobile devices, and equipment have proven to be the viable solution to a complex problem. Ultraviolet germicidal irradiation systems are a major capital investment; therefore, it is essential to understand the intended use of the UVGI system and whether it meets the specific needs of the hospital before equipment is purchased. It is critical to understand that regardless of the system being used or equipment effectiveness claims, the disinfection process will not be successful if the surface or items are not cleaned prior to UVGI disinfection.


  1. Downes A., Blunt, T.P. “The Influence of Light upon the Development of Bacteria.” Nature 16, 218 (1877). https://doi.org/10.1038/016218a0
  2. Ahmad, Q., Zubair, F., Amina Asif, A, Khalid Khan, J., and Imran, F. “Microbial contamination of mobile phone and its hygiene practices by medical students and doctors in a tertiary care hospital: A cross-sectional study.” Computer Methods and Programs in Biomedicine Update, Volume 1, 2021. https://www.sciencedirect.com/science/article/pii/S2666990021000379

Mary Olivera, MHA, CRCST, CHL, FCS has over 30 years of experience in numerous roles in healthcare sterile processing, distribution, and materials management. Ms. Olivera participates in monitoring, surveying, and training interdepartmental staff in the proper cleaning, decontamination, and sterilization practices, and has been highly committed to the standardization of interdepartmental processes. A regular recruit on expert panels regarding sterile processing and a past president of the New York State Central Service organization, she continues to play a major role in promoting higher educational requirements for central service professionals to increase patient safety.

Ms. Olivera brings to the table extensive knowledge of Joint Commission, DNV-GL, AAMI, OSHA, CDC, and DoH regulations. She specializes in budgeting, change management, inventory management, process re-engineering, program and project management, vendor relationships, quality control, Six Sigma, supply chain, and total quality management.

Ms. Olivera is an educator and has published numerous articles related to sterile processing, surgical services, process improvement, and guides to achieve successful accreditation surveys.

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