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Kevin Kahn

intErview with Kevin Kahn frOm Crystal is discussing uv-c led technolOgy and its applicAtions.

Respiray spoke to Dr Kevin Kahn, Market Development Manager, EMEA at our LED producer, Crystal IS, part of the world-renowned Asahi Kasei Group. We discussed how UV-C LED technology is applied to battle current and future pandemics.

Crystal IS is one of the world’s leading UV-C LEDs manufacturers that produces the highest quality ultraviolet LEDs that Respiray uses to inactivate viruses and bacteria.

What is your background?

My background is in semiconductor physics, my doctoral work and academic research focused on the class of materials behind the development of UV-C LEDs.

What is your role at Crystal IS?

I’m the Market Development Manager for EMEA and responsible for activities around air treatment. 

Who and what are Asahi Kasei and Crystal IS?

Crystal IS is a pioneer in developing and commercialising high-performance UV-C LEDs and is part of the Asahi Kasei Group, a Japanese technology company. The company has a global footprint, and we currently work across two main applications:

  1. disinfection of surfaces, air, and water
  2. environmental monitoring and instrumentation

What makes us unique is our strong focus on microbiology, with an in-house microbial lab and an expert team working to understand pathogens so that we can develop products specific to the requirements of the markets we serve. 

Asahi Kasei is a longstanding company, almost 100 years old and with 44,000 employees globally. Crystal IS and Asahi Kasei missions are well aligned: improving sustainable lives and healthy living worldwide.

How does UV-C disinfection work?

UV-C disinfection has been successfully used for about 100 years, from the early 1930s with traditional mercury lamps and now with solid-state devices like UV-C LEDs. 

UV-C radiation causes damage to the DNA and RNA of pathogens like viruses and biological micro-organisms and prevents them from replicating, effectively inactivating the pathogens. This process is quantified by what the industry calls log reduction values – the ratio of pathogens being inactivated from the initial population. This is how we typically measure the effectiveness of UV-C disinfection.

UV wavelengths are not equal – why?

Not all wavelengths are equally effective for the destruction of pathogens. The maximum germicidal efficacy is around 265nm and the wavelength range between 250 and 270 nm is known as the germicidal range where UV absorption can generate a solid disinfection level.

As we go beyond these wavelengths into UV-B, the germicidal efficacy decreases rapidly and the impact towards disinfection is close to zero.

UV-C is getting more global attention. Why?

UV-C and in particular UV-C LEDs have seen strong demand from the water industry in recent years, allowing novel solutions to ensure disinfection at point-of-dispense. With the global COVID-19 pandemic, this focus has shifted towards air disinfection.

Treating air is critical for several reasons:

  1. Aerosols are the primary mode of transmission for viruses such as SARS-CoV-2, influenza and tuberculosis, for instance.
  2. Infectious viral particles can remain aloft for hours. Relying on natural ventilation will be inadequate because the risk of infection remains high even after an infected person leaves the room.
  3. The long-range transportation of these viral particles means that close contact is not necessary for transmission.

This is putting UV-C LEDs back into the spotlight for their essential role in applications and devices that reduce the risk of aerosol transmission. 

Does the use of UV-C correlate with lower transmission risks? 


However, it is not straightforward because transmission risk is not a measurable quantity. 

Additionally, the industry needed first to define what disinfection meant in air quality:

  • What concentration is sufficient to reduce the risk? 
  • How long can the disinfection process take before successful pathogen transmission? 

Typically air quality was the problem of the heating, ventilation and air-conditioning (HVAC) industry. Although they have an important role to play, HVAC devices alone cannot meet the challenges and comply with new guidelines from the WHO, CDC and building requirements on air quality.

Technology is now playing a pivotal role in bridging that gap by using UV-C to accelerate the pathogen dilution process, effectively supplementing existing ventilation to reduce airborne transmission risk. 

This risk has two main components: proximity and one due to the average concentration present in the air. Wearable devices like Respiray UV air purifier for viruses allow reducing the first one by “shielding” people from an airflow perspective while reducing the second as more of these devices are present in the room and work together to renew the air faster.

What is the Kahn-Mariita (KM) model and its findings?

We built a unified view of the problem to quantify the impact of UV-C output in reducing airborne pathogen transmission and improving energy efficiency for healthy buildings.

Simply put, Dr Richard Mariita and I built an equivalent ventilation model that simulates air quality in a space over time, linking the performances of a device to that of a space and optimising parameters to find the most energy-efficient solution. The two main learnings from the KM model are:

  1. single-pass performance is not an appropriate metric of disinfection performance. While it can be readily measured, it provides the wrong incentives to offer low recirculation rate devices with high disinfection performances. The problem is that it does not consider the time required to treat a shared space, and therefore needs to be converted into an equivalent space ventilation rate (eqACH) to evaluate the real benefits.
  1. These systems all have an inherent bottleneck that prevents the effective use of improved power sources. In short, more UV does not always translate into better performances (as measured in eqACH), and a system will saturate. This is particularly important toward optimising solutions given the constraints system engineers must work with and design for end-user requirements.

But is UV-C safe? It has been incorrectly labelled as ‘unsafe’ – how do you respond to such claims?

It is important to say that UV-C is dangerous, which is why it works so well at inactivating bacteria and pathogens! 

However, it can be used very safely, as it has been done for decades if properly installed. Additionally, ample regulations on direct UV-C exposure ensure that the risk is adequately managed.

For instance, one solution is to simply enclose UV-C within devices to fully contain UV-C and not harm humans. An example of such a solution is the Respiray product. UV-C is prevented from leaking away from the device and thus cannot harm wearers at all.

Another example is to guide the radiation in specific regions where there is no risk of direct exposure to humans, such as upper-air UVGI.

At Crystal IS, we are trying to educate people on its safety and effectiveness. Sadly the COVID-19 pandemic saw the emergence of ‘so-called’ solutions that were inappropriately designed and may have caused risk.

Crystal IS only works with respected companies that operate ethically and introduce UV-C LED technology solutions safely. We know then that the products that reach end-users are both practical and safe. 

It is also important to point out that safety goes beyond UV-C radiation and includes ozone generation (UV-C LEDs do not generate ozone but other light sources like certain mercury lamps may) and protocol around disposal at devices end-of-life or unexpected failure for traditional light sources. 

I am confident that as the consequences of the pandemic remain, we’ll see demand for higher standards and those unsafe devices slowly disappear.

What is the greatest challenge for the industry?

The greatest challenge is to educate the industry as people do not understand or trust what they don’t see. When we discuss air treatment, it is complicated to know how it works precisely and quantify its long-term benefits.

Will people accept that our shared environments have changed and see the value in such products? 

We start to see trends in that direction.

Do you see an increase in wearable UV tech or more in non-wearable tech?

I see both. 

Facilities generally require an ongoing level of protection, so both forms of tech will only increase.

For example, a survey in the USA highlighted that the average air changes per hour (ACH) was 1.5, four times lower than the recommended rate of 6. Facilities, therefore, have to increase the safety of their spaces and need to use complementary technologies to retrofit current facilities that cannot be easily upgraded. 

Both technologies will co-exist as they serve slightly different purposes.

Wearable tech and UV-C LED technology plays a crucial role in effectively making a shield between infected people and those who are not – reducing the proximity risk from one person to another. Respiray is one such product that controls the air inhaled and treated, reducing this proximity risk. 

What sectors do you see growth in?

We have seen a growth in demand for UV-C in offices, schools, industrial use cases, such as food packaging, automotive and, of course, hospitality, like hotels.

Honestly, we see a demand for UV-C across all sectors.

How do you see the future of UV-C LED technology?

Pessimistically speaking, I see more pandemics and short term solutions will not be sustainable.

UV-C then has a vital role to play in fighting future pandemics and ensuring the disruption to our lives is minimised. It is a viable long-term solution because of the efficacy of the devices and their reduced cost.

UV-C LED technology use will also increase and disrupt a lot of industries relying on older UV light sources. The problem with mercury lamps is that they were used without interest for energy efficiency or environmental concerns. Now, end-users demand more energy-efficient devices that can be used in a more dynamic, flexible way.

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