Ensuring uniform UV energy distribution is the key to proper disinfection

April 28, 2020

By Gerry DiBattista, Vice President of Marketing, PTFE Business

For many decades, UV light has been a known disinfectant for air, water and surfaces that can help to mitigate the risk of acquiring or transmitting an infection.  Widely used in hospitals, water treatment plants and laboratories, UV disinfection is now moving into many more mainstream application areas.  For example, airlines are beginning to fit restrooms with UV lighting while not in use; most water purification companies are adding a UV option for point-of-use (POU) drinking water applications; and many air purification systems are adding UV to boost airborne disinfection.  The topic of surface disinfection exploded in 2020 with the COVID-19 pandemic, and today just about everyone is learning about the effectiveness of UV in disinfection.

The key to UV disinfection

The key to disinfection using UV energy is to have the proper wavelength and dosage to deactivate pathogens.  Most pathogens are responsive to very specific wavelengths of energy, almost all within the UV-C wavelength band between 200-300 nm.  And not only is the wavelength important, but the amount of energy the target receives is also critical.  The “deactivation” energy – or the dosage amount needed to ensure a certain log percentage decrease in activity, is measured in mJ/cm2.  If that surface or piece of equipment does not receive the correct wavelength and dosage, then disinfection is not assured.  The type and amount of energy needed was well documented by a study sponsored by the IUVA organization titled:  “Fluence (UV Dose) Required to Achieve Incremental Log Inactivation of Bacteria, Protozoa, Viruses and Algae”.

Ensuring proper UV dosage

So the question becomes – how do you insure proper dosage?  The number of disinfection units one can buy has increased exponentially over the past 10 years.  The key in ensuring proper disinfection is making sure the UV-C energy is spread uniformly throughout the reaction chamber – whether the target area is air, water or a surface.  Historically, the source of this UV-C energy has been a Mercury type lamp – which look similar to a fluorescent bulb.  These tend to be large, fragile, and have disposal issues.  More recently, UV-LEDs have come onto the scene and are mercury free and more energy efficient, however, the light tends to be concentrated in a near point source.  So – how to you efficiently spread this UV-LED light?     

Due to UV-C aggressive behavior to most plastic materials, most UV reaction chambers are made of metal such as aluminum or stainless steel.  There are multiple problems with these materials – namely their reflectivity is modest (between 30-70%) and their reflection is mostly specular – which means energy bounces off at the angle that it hits the surface (like a billiard ball hitting a bumper).  This specular reflection leads to so-called “hot spots” or “cold spots” where energy levels are well above or well below the dosage needed.  Thus, to ensure proper spreading of the UV energy and thus the dosage, energy needs to bounce off the surface many times (every time losing up to 70% of its energy – or an average of 2-5 bounces) so that all angles are covered.  This ends up requiring a lot of total energy due to these inefficiencies.

Using microporous PTFE

The more sensible solution is Porex Virtek® microporous PTFE, which unlike many polymer materials, does not break in the 200-300 nm UVC range.  Porex Virtek PTFE is highly reflective media, up to 97% in the UV-C range – meaning the UV energy can bounce off the surface multiple times (only losing 3% per bounce or lasting an average of 33 reflections) until it hist its intended target (i.e. the pathogen).  Secondly, Porex Virtek PTFE is almost an 100% diffuse reflectance – which means that, when the UV energy strikes the surface, it is reflected in a random diffuse pattern.  Therefore, regardless of the angle with which the light hits the surface, the UV energy is reflected uniformly in all directions.  Watch a demonstration of this reflectivity in the video below:

What this ends up meaning is this – much less initial UV energy is needed since the surface reflectivity is so high and a uniform dosage will occur since energy is reflected in all directions.  Some manufacturers in this space have claimed needing several less UV-LEDs or being able to use lower wattage LEDs in their design when using Porex Virtek PTFE to line their reactor versus other materials – saving both money and energy and ensuring the safety of the end product.

I’m so proud to say that our POREX® Virtek PTFE makes the world safer, healthier and more productive by setting a new standard of efficiency in disinfection equipment designed to destroy the COVID-19 virus and flatten the curve.  Our reflective media helps to ensure these disinfection chambers are delivering the proper amount of UVC energy to every nook and corner to insure pathogen deactivation.