What is UVGI?
Ultraviolet germicidal irradiation (UVGI) improves air quality by blasting microorganisms with a short wavelength of UV radiation.
Traditionally this form of disinfection is used in the food preparation business and hospitals where cleanliness is of utmost importance. However, more people are starting to see the benefits of using UV lighting in their own homes to improve air quality.
UVGI radiation (also called UV-C) is harmful to microorganisms; the UV radiation damages their DNA in such an extreme way that it kills them. It is similar to the process that results in UV damage to skin cells in humans that can lead to cancer; UV radiation from the sun, over a prolonged period, can cause DNA damage to skin tissue and the result in cancerous growth.
In the case of microorganisms, the UV damage leaves them unable to perform cellular functions and they quickly die. The human equivalent of the damage that occurs in microorganisms is that we would no longer being able to breath or transport oxygen to the cells.
UVGI does not pose a natural risk to microorganisms because the Earth’s atmosphere blocks most of it so that it is not concentrated. However, when the UV is in close proximity to microorganisms such as molds, viruses and pathogens, it is deadly.
UVGI has been used in water disinfection for many decades and has been widely used in medical sanitation and to sterilize drinking water. It is only recently that engineers have developed systems that can effectively kill microorganisms that are carried in the air.
To understand what is happening with UV light we need to understand a little about the electromagnetic spectrum. UV waves are a form of electromagnetic radiation that is shorter than visible light. The shortest wavelength that we can see is violet light (the last color of the rainbow) and the longest wavelength we can see is red (the first color of the rainbow). Infrared is the wavelength that is longer than visible red, and ultraviolet is the wavelength that is longer than visible violet. Ultra means “beyond” and infra “below”. Ultraviolet radiation is subdivided between Near Ultraviolet and Extreme Ultraviolet. Beyond ultraviolet are the shorter X-rays and then Gamma rays. At the other end of the spectrum, beyond infrared are the radio waves, which are used for radio communication.
How does it work?
The UV radiation that kills microorganisms is limited to the short range and is called UV-C. UV waves are only dangerous to microorganisms at certain wavelengths; at a wavelength of 254 nm (2,537 Angstroms) UV radiation breaks the molecular bonds in DNA within microorganisms.
When molecular bonds are broken and the DNA is damaged mutations occur. This damage causes mutations and damage that bacteria, viruses and other microorganisms cannot survive.
Germicidal lamps should be used in discreet locations about the home to kill microorganisms. If you have air conditioning or hot air central heating, placing the lamps within the vents will ensure that any microorganisms that have accumulated in the vents will be killed before they can be released into the house again.
UVGI lamps are never 100 percent effective. The speed of airflow past the lamp, the power of the UV rays and then wavelength will all have an impact on how many organisms can be killed. Also, if the air is thick with dust particles, the microorganisms may be shielded from the harmful rays.
It is important to keep the bulbs very clean because dust and grime on the bulbs will greatly reduce the power of the rays. Ideally air lamps should be cleaned at least monthly and the bulbs replaced annually.
It is important to place UVGI lamps in a location where they will be able to kill microorganisms but not where people will see them. Continued exposure to these lamps has been known to cause dermatitis (inflammation of the skin) and photokeratitis (a painful eye condition). The best place to install them is within forced air system vents, well away from where they can be seen.