Air disinfection by direct irradiation of upper-layer

Ultraviolet germicidal irradiation, or UVGI, is the use of ultraviolet (UV) energy to inactivate viral, bacterial, and fungal organisms. UVGI fixtures produce UV-C energy, which has shorter wavelengths than more penetrating than UV-A and UV-B rays. Upper-layer UVGI refers to a disinfection zone of UV energy that is located above people in the rooms they occupy. This kills airborne pathogens in the room where they are released. Fixtures are installed to prevent direct UV exposures to people in the room.

How does upper-layer UVGI work?

1. Air passes through the disinfection zone from air flow through HVAC system, fans, and/or open windows.
2. The airborne pathogens are killed once they receive an appropriate amount of UV energy. The particles remain in the air, but they are no longer infectious.

For airborne viral particles, upper-layer UVGI systems provide air changes per hour that are similar to the introduction of clean air into the space.

Considerations for use of upper-layer UVGI

• The most important locations for UVGI are high-risk indoor settings. These include:
  
  
  • Areas with an increased likelihood of sick people (for example, school nurse’s office, hospital waiting room).
  • Crowded spaces, particularly when the health status of occupants is unknown (for example, courtrooms, lobbies, homeless shelter sleeping areas).
  • Spaces where people must take off masks to eat or drink (for example, school/institutional cafeterias, restaurants, break rooms).
  • Areas where it is difficult to stay at least 2 meters apart from others.
    
    
• UVGI is recommended in spaces with insufficient or no mechanical HVAC systems or where adequate natural ventilation cannot be maintained year-round. Spaces must be at least 3 meters tall, but a minimum ceiling height of 3.25 meters is preferred, with some airflow to move air (for example, fans at low speed). Upper-layer UVGI is not necessary in open-air environments, such as outdoor open-air seating areas.
• If the HVAC system allows for efficient filtration or provides outdoor air flow above minimum code requirements, it will remove most airborne virus particles and upper-layer UVGI would not add as much benefit.

Implementation considerations

• Upper-room UVGI systems have been used safely and effectively for decades. However, UV energy directed or reflected into the occupied space has the potential to cause temporary eye or skin damage. Proper installation by manufactures specification will UV energy is directed above occupied space and operates safely.
• The systems should be connected to designated electrical switches with limited access to the public and staff or volunteers not trained in managing the system. For example, consider using lockable switches or placing switches in a restricted area that only trained staff can access using a lock and key. This prevents the UV lamps from being turned on or off unintentionally and allows the fixtures to be safely powered off when necessary without fear of them being powered on during maintenance.
• Influenza viruses are more susceptible to UV energy than the bacteria that causes TB. Thus, any upper-room UVGI system installed to help during the COVID-19 pandemic will also be useful against seasonal flu, if it is properly maintained.
• UV-C energy can damage plants placed in the disinfection zone (for example, on the top of tall bookcases or high shelves). The energy can also cause fading and cosmetic blemishes to wood surfaces and wallpapers (most wall and ceiling paints are not affected). Thus, care should be taken when installing upper-room UVGI systems in spaces with ornate architectural elements and plants.

Our recommendation

UV FLOW – unidirectional flow UV-C system

UV-FLOW series includes the possibility to choose among unidirectional flow devices, different according to the UV-C
lamp powers. UV-FLOW has a stainless steel structure and is equipped with unidirectional black honeycomb filter, which channel the flow of UV rays. UV-FLOW achieves the elimination (99%) of bacteria such as Bacillus, Coli, Clostridium, Legionella, Vibrio, Salmonella, Pseudomonas, Staphylococcus, etc. in just a few minutes of operation.

The installation, owing to special brackets which direct the flow, can be made so to form a “UV blade”, which, starting from the device, radiates towards the floor (UVC barrier) or towards the ceiling, if the top layers of the room are to be treated.
Pointing it towards the ceiling achieves a permanent disinfection of the environmental air, which circulates naturally
inside the spaces, following normal convective motions.

UV-FLOW series is the only one to be specifically designed with this double purpose. UV-FLOW does not require any special maintenance, except for the periodical replacement of the lamps, it is entirely built in Italy, with high quality and extremely resistant materials.

The use of UV-FLOW allows an intensive air disinfection, essential in all health and pharmaceutical environments, where it is necessary to operate in optimal microbiological conditions.
In the health sector, it is recommended to create a decontamination area between two different areas, especially if one of them is to be kept under strict microbiological control. The mold spores and bacteria, freely circulating among spaces, are destroyed by the UV-C rays; this avoids the possibility that they settle on the surfaces.

With UV-FLOW, it is possible to create a bactericidal barrier between “grey” and “white” areas in a simple, immediate and secure manner, or treat the air in general, without developing heat, without chemical and without any contraindications.
It is shown that the control and an increased of hygiene level allows a consequent and general increase in quality both in the health and pharmaceutical sector, in microbiological laboratories, etc.

Sources:

LIGHT PROGRESS

Centers for Disease Control and Prevention