Germicidal ultraviolet light systems, also known as UV germicidal irradiation (UVGI), are used to disinfect the air by using UV light at a very short wavelength to kill or inactivate microorganisms. They are most commonly used in places where it is vital that infection and disease be controlled, such as food preparation areas, water purification plant and hospitals. Because of the risk of airborne infection from heating and air conditioning ducts in homes, many people are now installing UV germicidal irradiation lights.
Another reason for a growing interest in UVGI is the threat, or at least the fear of such a threat, of a possible malicious release of bioterror agents. A more practical daily use of UVGI is to control tuberculosis and other airborne respiratory pathogens.
UVGI was first used in medical sanitation to help sterilize drinking water and wastewater but developments in more recent years have led to a growing interest in air sanitation.
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How does UVGI work?
UVGI emits short-wavelength ultraviolet radiation that damages the DNA in airborne pathogens by destroying nucleic acids that form them. The result is that the pathogens die because their vital cellular functions can no longer work.
UVGI does not naturally occur on Earth, or at least, it is very rare, because our atmosphere blocks most of the UV radiation that is received from the sun.
To be effective the UVGI needs to work over a period of time, which means that the lights need to be on for most of the day. You cannot effectively kill off the airborne pathogens with a quick blast from a powerful lamp; instead you need to leave the lamp for lengthy periods to ensure that maximum damage is done to microbes.
Because of this, UVGI lamps are not very effective in fast moving air and to overcome this problem many systems use an enclosed unit with shielded UV lamps that control the flow of air, although within forced air systems the lamps can be placed within vents to target air as it passes through.
It is also important to note that inside forced air systems there are usually many shaded areas because the UV light rays can only travel in straight lines. This means that there are many pockets where microbes can live and multiply, although if the atmosphere within the vents is dry it will not harbor many microorganisms.
Within air conditioning units, UV lamps are best placed within drain pipes and cooling coils because this is where moisture forms, which is a good breeding ground for many bacteria and microbes. UVGI lamps need a good filtration system to ensure that dead microbes are collected and safely disposed of.
Use a UV Light System to Prevent Mold
UVGI is often used specifically to destroy pathogens that cause disease, but it is also extremely effective at preventing mold from spreading. Mold, which breeds in warm and damp conditions, causes respiratory problems such as asthma and forms unsightly growths in the home.
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Types of UV Light System
There are several types of germicidal lamps for varying conditions. Some air purifiers include odor absorption and are ideal for use in kitchens as well as in homes with pets. Others are designed to attack surface mold that grows on cooling coils.
Many manufacturers are now making whole house furnace HVAC UV air purifiers that are installed inside air vents. These use large high-powered lamps that are installed in the center of air vents to ensure maximum effectiveness and are recommended in homes with forced air systems.
Things to Note About UV Systems
UV rays are harmful to humans because they cause damage to the skin. This is why most UVGI lamps should be shielded or used in environments, such as air vents, when there is limited human exposure. The short-term risks are burns and prolonged exposure over many years could cause skin cancer.
One of the greatest dangers is damage to the eyes. UV radiation causes extremely painful inflammation of the cornea and this can cause temporary blindness. UV rays can also damage the retina of the eye. It is therefore very important that lamps are never installed in areas where people will be exposed to them; especially if children are present.