Ultraviolet Germicidal Irradiation in Air Conditioners (UVGI)

You must have heard of HEPA (High-efficiency particulate air) filter systems. Companies like Blue Star and Voltas use advanced ventilation intervention technologies like upper-room UVGI (Ultraviolet germicidal irradiation) in their air conditioners and air purifiers.

Let us discuss the UVGI concept in this article.

Before we discuss UVGI, let us understand ultraviolet lighting.

Ultraviolet Lighting

Everyone knows that UV rays constitute 10% of the total sunlight. We define UV light as electromagnetic energy with wavelengths longer than X-rays and shorter than visible light.

So, UV light has wavelengths between 10nm and 400nm. It is divided into three sub-bands, UV-A (near wavelengths), UV-B (middle wavelengths), and UV-C (far wavelengths).

Generally, the earth’s ozone atmospheric layer blocks UV radiation below 290nm (UV-B and UV-C). Therefore, UV light with wavelengths less than 290nm has germicidal properties. So UV germicidal lamps produce wavelengths between 200nm and 290nm (UV-C rays).

UV light kills bacteria and viruses by attacking the microbes’ DNA and RNA. It modifies the microorganisms’ genetic material and destroys their reproduction ability. It brings us to the concept of UVGI.

What is UVGI?

UVGI, or Ultraviolet Germicidal Irradiation, is a disinfection method that uses UV-C rays (short wavelength) to inactivate pathogens and microorganisms and kill them. Usually, UVGI is used for disinfecting surfaces, air, and water.

Air conditioners use upper-room UVGI to purify the air in the room by killing airborne pathogens. In addition, this technology disinfects the area above the people in the spaces they occupy, thus, preventing people from direct exposure to UV radiation.

The latest Blue Star AC models use this technology to provide additional protection. Primarily, UVGI applications emit shortwave UV rays with a wavelength of 254nm (Blue Star ACs use UV light at 253.7nm) to deactivate microbes and bacteria by damaging their DNA. We will not go much into the technical aspects but understand how UVGI works to purify the air in the room.

How does Upper-room UVGI technology work?

We have seen that upper-room UVGI represents the disinfection zone near the ceilings in the people’s rooms. So, UVGI technology works by disinfecting this zone and rendering the microbes and bacteria inactive.

• The AC system enables airflow through the disinfection zone and ensures that people occupying the rooms are not exposed to it.
• So, upper-room UVGI kills the airborne pathogens once they receive a specific amount of UV energy. Therefore, the particles remain in the air but are rendered ineffective.

The UVGI systems provide ACH (air changes per hour), similar to air purifiers.

What are the ideal locations for the use of upper-room UVGI?

Usually, UVGI technology is used in ACs installed in high-risk indoor settings. The examples include:

• Areas occupied by many sick people, like hospital waiting rooms and medical clinics
• Other crowded places like school classrooms, hotel lobbies, courtrooms, homeless shelter sleeping areas
• Eating spaces where people have to remove their masks, like restaurants, canteens, cafeterias, etc.
• Places where people find it challenging to stay at least six feet apart.

Can a household AC use upper-room UVGI technology?

Yes. Domestic ACs can use upper-room UVGI for air purification. However, one should ensure the ceiling height is 8.5 feet or more because there should be sufficient space for air circulation. Outdoor locations do not need ACs with UVGI.

Is UVGI required in ACs that already use efficient air purification systems?

ACs with efficient air purification systems like HEPA filters do not need additional purification technology like UVGI. The HEPA filters can take care of air purification. 

What is in-duct UVGI?

In-duct UVGI is a primary UVGI application designed to disinfect the air as it passes through the air conditioner system before recirculation. The best aspect is that in-duct UVGI is that it irradiates the entire cross-section of the AC duct at high intensities while ensuring not to affect the room occupants.

Different UVGI applications

Blue Star offers an extensive range of applications that use UVGI technology.

• UVGI Emitter – Blue Star has designed its latest range of UVGI emitters to deactivate viruses and bacteria within the air circulation system. Thus, it disinfects the air that circulates in the room. Blue Star UV germicidal emitters are installed downstream from the cooling coil on the system’s supply side.
• Emitters in AHUs and FCUs – Blue Star UVGI emitters are installed in AHUs (air handling units) and FCSs (fan coil units) to deactivate viruses and prevent their proliferation inside the coils and drain pans. In addition, UVGI emitters destroy all pathogens entering the system and settling on the coils to eliminate regular manual cleaning.
• UVGI emitter for ducts – Blue Star ACs have an in-duct UVGI system to disinfect air passing through the vents and ensure the recirculation of pure air in the rooms.

Besides, Blue Star offers UVGI solutions for surface and mobile air disinfection.

Advantages of UVGI technology

UVGI technology in Blue Star ACs offers the following benefits.

• Convenient to operate
• Ability to use across large spaces
• Rapid process
• Minimizes exposure to room occupants and workers,
• No ozone output  
• Long service life

AC models from Blue Star with UVGI

Blue Star offers UVGI technology in its latest YBTUUV series.

Other AC models using UVGI technology

Besides Blue Star, other AC models with UVGI technology include:

• LG UV Nano Inverter Split AC uses UV Nanotechnology in its latest variants, LG PS-Q19UWZF AI Convertible 6-in-1 split AC.
• Haier HSU18F-UVSW4B (INV), the latest variant from Haier, uses UV technology to purify the air circulating in the room.
• Daikin FTKN 50U uses a patented technology known as Streamer Discharge Technology to eliminate bacteria and viruses. This technology is similar to UVGI.

Conclusion

UVGI technology in ACs helps eliminate bacteria and viruses from the air circulating in the room. This technology is available for split ACs alone. But, users should note to install these ACs at a height of at least eight feet from the flooring to keep the disinfectant area as far away from the room’s occupants as possible.

References

https://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradiation

https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation/uvgi.html

https://www.bluestarindia.com/media/294805/uvgi-emitters.pdf