Design optimization and validation of UV-C illumination chamber for filtering facepiece respirators

Abstract

In this study, we constructed an UV-C illumination chamber using commercially available germicidal lamps and other locally available low-cost components for general-purpose biological decontamination purposes. The illumination chamber provides uniform illumination of around 1 J/cm² in under 5 min across the chamber. The control mechanism was developed to automate the on/off process and make it more secure minimizing health and other electrical safety. To validate the decontamination efficacy of the UV-C Illumination Chamber we performed the Geobacillus spore strip culture assay. Additionally, we performed the viral load measurement by identifying the COVID-19-specific N-gene and ORF1 gene on surgical masks. The gold standard RT-qPCR measurement was performed to detect and quantify the COVID-19-specific gene on the mask sample. The biochemical assay was conducted on the control and test group to identify the presence of different types of bacteria, and fungi before and after exposure under the illumination chamber. The findings of our study revealed satisfactory decontamination efficacy test results. Therefore, it could be an excellent device in healthcare settings as a disinfection tool for biological decontamination such as SAR-CoV-2 virus, personal protection equipment (PPE), (including n95, k95 respirators, and surgical masks), and other common pathogens.

Keywords: Biological decontamination and pathogens; Decontamination efficacy; Facepiece respirators; Personal protection equipment (PPE); SAR-CoV-2 virus; UV-C illumination chamber.

Fig. 1

Final prototype of UVC disinfection chamber. The image left without illumination (a) and right after illumination (b) shows the UV-C chamber.

Fig. 2

A primary control circuit schematic. The Proteus schematic and simulation confirms the status of 16 LED on/off state. The LCD and CB were used for notification and safety purposes.

Fig. 3

PCB design of control mechanism (a) and hardware of the control mechanism (b).

Fig. 4

Safety Box at left (a) which includes on/off switch and LED status indicator in right magnified (b) which shows the temperature and humidity inside UV-C chamber.

Fig. 5

Flowchart of sample collection and subsequent RT-qPCR amplification. The workflow starts with sample collection then sample preparation. Sample preparation is followed by RNA extraction and master mix preparation. After that RT-qPCR amplification was done and upon the observed result, mask sample with positive result underwent UV-C irradiation. The irradiation process is followed by sample preparation to result interpretation.

Fig. 6

Placing GUVA-S12SD model UV sensor at different location: (a) bottom. (b) Middle and (c) right.

Fig. 7

UV and total intensity due to activation and deactivation of UVC light.

Fig. 8

The Geobacillus spore strips were incubated, and media was observed. Group 1 (3 strips) was incubated for 10 days at 50 °C and group 2 (3 strips) was incubated for 7 days at 50 °C. The Geobacillus spore strips used in a.1, a.2, b.1, and b.2 underwent UV type C irradiation. After incubation, showed a transparent purple color indicating no bacterial growth. The Geobacillus spore strips used in a.3 and 8b.3 as control were not exposed to UV type C irradiation. Thus, showed a yellow color indicating the presence of bacterial growth. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 9

Viral load is represented as amplification graphs of RT-qPCR. Internal Control (IC) gene, N gene and ORF1ab gene are shown in purple, yellow, and blue color respectively in the graphs. The RT-qPCR results of mask samples before the UV-C exposure are shown in a.1, b.1, c.1, d.1 and c.1. On the other hand, the results of UV-C exposed mask samples are projected in a.2, b.2, c.2, d.2 and e.2. The presence of the N gene is observable in a.1, b.1, c.1, d.1 and c.1. ORF1ab gene can be seen in a.1, b.1, c.1 and d.1. Internal Control gene is observable in a.1, b.1, d.1 and e.1. The ORF1ab and IC gene are nonexistent in a.2, b.2, c.2, d.2 and e.2. Also, the N gene cannot be found in a.2, b.2, c.2 and d.2. All the related CT values can be found in Table 1. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 9

Viral load is represented as amplification graphs of RT-qPCR. Internal Control (IC) gene, N gene and ORF1ab gene are shown in purple, yellow, and blue color respectively in the graphs. The RT-qPCR results of mask samples before the UV-C exposure are shown in a.1, b.1, c.1, d.1 and c.1. On the other hand, the results of UV-C exposed mask samples are projected in a.2, b.2, c.2, d.2 and e.2. The presence of the N gene is observable in a.1, b.1, c.1, d.1 and c.1. ORF1ab gene can be seen in a.1, b.1, c.1 and d.1. Internal Control gene is observable in a.1, b.1, d.1 and e.1. The ORF1ab and IC gene are nonexistent in a.2, b.2, c.2, d.2 and e.2. Also, the N gene cannot be found in a.2, b.2, c.2 and d.2. All the related CT values can be found in Table 1. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)