UV Bandpass Filters for Sterilization
 

Ultraviolet (UV) light has been used effectively for line-of-sight sterilization of rooms, objects, and skin for over a century, but these higher energy photons can also cause severe sunburn and skin cancer. Fortunately, UV light at 222nm is capable of sterilization without harming human skin, making it a safe and effective technology to combat bacteria and viruses, including COVID-19.  Optical filters can be designed to transmit the desired UV frequency while blocking the harmful wavelengths.

The UV section of the electromagnetic spectrum lies between x-rays and visible light, from 100nm to 400nm. British researchers Arthur Downes and Thomas Blunt discovered the sterilization properties of UV light in 1878 and Danish doctor Niels Finsen won the 1903 Nobel Prize in Medicine for employing UV light in the treatment of skin disease. When high energy photons in the 100nm to 315nm range are absorbed by living organisms, they partially destroy the cellular DNA. A cell having damaged DNA cannot function effectively; they lose their reproductive capacity and eventually die. Consequently, UV light is considered to be an extremely effective method of killing bacteria and viruses. Several studies ^{(1, 2, 3)}have determined that the UVC range of 200nm to 280nm is most effective for sterilization. They have also concluded that some UV radiation causes damage to human skin.

Research ⁽¹⁾has shown that emission at 222nm from an excimer lamp is capable of sterilization without penetrating to the skins basal layer. To prevent harm to the patient, the emission spectrum needs to be filtered to suppress the damaging longer wavelengths that are capable of dermal penetration. This can be achieved using a 222nm UV bandpass filter Part # 222FVN offered by eSource Optics.

• “Germicidal Efficacy and Mammalian Skin Safety of 222nm UV Light” - February 2017,
  S. National Institute of Health national Library of Medicine

• “Testing Novel Inventions to Protect Workers from Airborne Infections” - January 2018, 
  S. Dept. of Health & Human Services, CDC
   
• “Ultraviolet Germicidal Irradiation – Current Best Practices” – August 2008, ASHRAE Journal