How UV-C affects microorganisms and inactivation mechanism

UV-C (between 100nm and 280nm) is not observed in nature because it is absorbed by the ozone layer in the atmosphere. This range is called germicidal because it has the ability to inactivate microorganisms such as viruses and bacteria. In humans this radiation is absorbed by the epidermis and prolonged exposure can cause burns, skin irritations, cataracts, and eye infections.

When a cell is subjected to UV-C radiation, it penetrates the cell wall and its energy is absorbed by proteins and the cell’s DNA. The UV-C light damages the protein structure and the DNA undergoes a chemical change, breaking its molecular bonds. The photochemical damage caused to the nucleic acid prevents its replication.

The effectiveness of this UV-C disinfection process depends on the intensity of the radiation, exposure time, relative humidity, and the presence or absence of shadow areas and particles that can shield the microorganisms from the radiation. In the case of viruses, studies show that the type of nucleic acid (double-stranded or single-stranded DNA and double-stranded or single-stranded RNA) also interferes with the effectiveness of UV-C radiation.

The action of UV-C is hindered by shadow areas, i.e. areas that are not 100% exposed to UV-C light. The greater the degree of shading (partial shadows), the longer it takes to reach the dose needed to inactivate the particles. In the case of total shadows, the UV-C does not act.

UV-C Dangers and Protection

UV-C is dangerous for living beings (people, animals and plants). Therefore, it must be ensured that they are not exposed to UV-C for too long. On the other hand, UV-C is extremely easy to stop! All it takes is one acetate to do it. The maximum daily dose that humans can be exposed to, according to the European parliament’s directive 2006/25/EC, is 6mj/cm². The consequences of excessive exposure are damage to the eyes (possibility of cataracts) and to the skin (sores). Only exposed parts of the body are likely to be affected. Dynasys has instrumentation that measures the UV-C doses received and indicates how long a person with exposed body parts can stay in the room without danger.

The advantage of Far-UVC (222 nm) is that it is harmless to humans and animals. That is, Far-UVC does not cause skin burns or affect the eyes. Prof. David Brenner’s group at Columbia University has been conducting tests that are intended to demonstrate this. However, this has not yet been recognized by the FDA and so the daily dose is still limited to about 22mj, which is insufficient for most situations.

Instrumentation – Dosimeters and EU Directive 2006/25/EC

Dynasys uses and markets instrumentation manufactured and certified in the European Union. The instrumentation includes a wireless dosimeter with cosine correction. This equipment measures instantaneous power and cumulative dose. Being wireless allows measurements to be made in complete security.

The second device we use detects UVC radiation in workplaces and in accordance with the European Parliament’s Directive 2006/25/EC on minimum health and safety requirements regarding workers at risk of receiving UVC radiation. Dynasys uses this equipment to ensure that no UVC radiation leaks out of equipment developed by Dynasys.

Dynasys is also available to evaluate custom projects in this area.

Contact us!

CleanCloset: Disinfection Cabinet

The goal of CleanCloset is to disinfect easily, quickly (1 to 2 minutes) and effectively. It works on various types of objects (clothing, computers, toys, perfumes, others) and for different types of microorganisms. Tests have been done with SARS-CoV-2 on porous and non-porous surfaces and with the antibiotic resistant bacteria, Staphylococcus aureus and Klebsiella pneumoniae, on non-porous surfaces. It is intended for both small and large stores.

The CleanCloset is a cabinet in zincor plate with 2mm thickness and electrostatic painting. The door is made of polycarbonate. The cabinet, including the door, is completely sealed against UV-C. This has been proven by the instrumentation we have, a dosimeter and equipment that allows verification of the 2006/25/EC standard.

The outside dimensions of the cabinet are: 810mm x 810mm x 1850 mm (width x depth x height). The inside dimensions are: 620mm x 620mm x 1500mm.

The Cabinet has four 1200mm 36W UVC lamps arranged vertically on the four vertices. Each lamp has a reflective frame, and the inside of the cabinet is lined with reflective film. This maximizes the instantaneous power that reaches the objects to be disinfected.

The disinfection cycle depends on the type of objects to be disinfected and the type of microorganism targeted. The tests were performed for SARS-CoV-2. The disinfection rate for clothing and SARS-CoV-2 is 88.75%! This rate was achieved with a dose of 66mj/cm2 on the front and a dose of 66mj/cm2 on the reverse. This dose is achieved in about 30s. The tests were performed on tissue.

The antiviral activity concerning SARS-CoV-2 was verified by the Institute of Molecular Medicine (Lisbon, Portugal).

Tests were also carried out at CITEVE – Technological Center for Textile and Clothing Industries of Portugal – regarding the effects of UV-C on fabrics. No significant changes were detected up to 1400mj/cm2 and namely in terms of:

  • Resistance and elongation to rupture and dimensional stability
  • Colorimetric Evaluation, DE

In terms of color, the variations between the exposed areas and the areas 100% in shadow were specially analyzed and once again no variations were detected to the naked eye and no relevant variations were measured.

The fabric used in the tests is made up of Polyamide / Elastane / Polyurethane

The CleanCloset cabinet has a 7″ touch screen monitor, a Windows 10 Pro PC, a controller and a barcode scanner / QRcode.

In the case of CleanCloset – Clothes, the employee begins by swiping the label on the clothes to be disinfected through the barcode scanner.

The software checks the database to see if that piece of clothing is in the “not disinfected” state. If it is, the employee can proceed with the disinfection process by placing the garment on a hanger that hangs inside the equipment. Close the door and start the process!

Once the first phase of the disinfection process is finished, the software asks the employee to remove the garment, turn it inside out, put it back inside the closet, and disinfect it again.

At the end of the process, the software records that garment as disinfected. The software runs in the cloud. All interfaces work via a browser.

For the fitting rooms, a HoneyHell EDA51 barcode/QR SCAN reader with android-based touch screen is provided for Employees to register the garments going into the fitting rooms as “not disinfected”. The touch screen also allows employees to characterize the Customers who are tasting the garments. The software runs via a browser.

The BackOffice allows you to register garments manually or via ERP integration. Provides statistics. It allows managing users and their passwords, consulting events, defining clothes properties (type, color, disinfection program, gender, etc).

Dynasys is also available to evaluate custom projects in this area.

Contact us!

Portable Germicide

This is a simple, cost-effective solution that can inactivate 99% of SARS-CoV-2 viral particles on surfaces with a single pass within 5cm of the target. It can also kill SARS-CoV-2 viral particles in aerosols in rooms or offices in about 15 minutes (depending on the area of the room).

The equipment operates on 230 Vac. To turn on the lamp a button has to be pressed continuously. This prevents the lamp from being left on by forgetting. The person operating the equipment must have all exposed parts of the body protected. Otherwise he/she is at risk of exposure to UVC via reflection. There should be no other people present in the room!

UV-C is extremely easy to block, for example with a covid-19 type protection visor. For arms and legs not covered by clothing a simple raincoat can be used. The hands should be protected by simple gloves.

This equipment can be used to disinfect workstations, computers, keyboards, documents, tools, clothes, correspondence, rooms, car interiors, etc.

Tests have been conducted with SARS-CoV-2 on porous and non-porous surfaces and with resistant bacteria strains, Staphylococcus aureus and Klebsiella pneumoniae on non-porous surfaces.

Dynasys – Engenharia e Telecomunicações, S.A.

Centro Empresarial Sado Internacional – Edifício E4

Estrada Nacional 10, Vale da Rosa

2910-835 Setúbal, Portugal

Tel: +351 265 706 900

Fax: +351 265 706 909