From left to right: María Teresa Flores-Arias, Justo Arines and Carmen Bao-Varela
Our research group, Photonics4life, are members of the Physics Faculty at the Universidade de Santiago de Compostela. During the lockdown, due to the Covid-19 pandemic disease, we were involved in the development of a UVC sanitizing chamber that was used to disinfect protective face masks at the University Hospital of Santiago de Compostela in Galicia (Spain).
In those days, the shortage of masks forced our health professionals to reuse masks. Dr.Aurora Baluja developed a sanitizing mask chamber with UVC mercury lamps. The Photonics4life team of the USC was requested to radiometrically characterize this chamber. The research team used the StellarNet SILVER-Nova Spectroradiometer (supplied by the distributor Iberoptics Sistemas Ópticos) to determine the irradiance distribution over the face masks and to determine the exposure time in accordance to the dose proposed by the physicians community.
Photonics4life team is a multidisciplinary research group involved in several branches of photonics including, light pollution, visual optics, laser processing and 3D printing.
The following is a preview of their research found here
UV light dosage distribution over irregular respirator surfaces. Methods and implications for safety.
Aurora Baluja(a), Justo Arines(b), Ramón Vilanova(c), Carmen Bao(b), Maite Flores(b)
Background and Objectives
The recent pandemics have lead to a global decrease in protection ware, especially facepiece filtering respirators (FFRs). Ultraviolet-C wavelength is a promising way of decontamination, however adequate dosimetry is needed to ensure balance between over and underexposed areas and provide reliable results. Our study demonstrates that UVGI light dosage varies significantly on different respirator angles, and propose a method to decontaminate several masks at once ensuring appropriate dosage in shaded zones.
Methods
An UVGI irradiator was built with internal dimensions of 69.5 x55 x 33 cm with three 15W UV lamps. Inside, a grating of 58 x 41 x 15 cm was placed to hold the masks. Two different respirator models were used to assess irradiance, four of model Aura 9322 3M of dimensions 17 x 9 x 4cm, and two of model SAFE 231FFP3NR with dimensions 17 x 6 x 5 cm. A spectrometer STN-SilverNova was employed to verify wavelength spectrum and surface irradiance. A simulation was performed to find the irradiance pattern inside the box and the six masks placed inside. These simulations were carried out using the software DIALUX EVO 8.2.
StellarNet Team tested light emission from some affordable UV wands to test their sanitization capability. Read the App Note
Results
The data obtained reveal that the dosage received inside the manufactured UVGI-irradiator depends not only on the distance between the luminaires plane and the base of the respirators but also on the orientation and shape of the masks. This point becomes relevant in order to assure that all the respirators inside the chamber receive the correct dosage.
Conclusion
Irradiance over FFR surfaces depend on several factors such as distance, angle of incidence of the light source. Careful dosage measurement and simulation can ensure reliable dosage in the whole mask surface, balancing overexposure. Closed box systems might provide a more reliable, reproducible UVGI dosage than open settings.
The entire article is found here
