The average person will probably not know much about ultraviolet (UV) light other than that. It is the type of light that burns your skin if you forget to apply sunscreen on a hot day. While it can be harmful to the skin, however, UV light also has some incredibly useful applications. Ranging from water purification to sterilization of surgical equipment, UV rays are used today in a wide range of technologies for their strong microbe-killing properties.
One UV technology that has seen a massive spike in interest in recent months due to the coronavirus health crisis is the UV lamp. These lamps are marketed on the premise that they can improve indoor air quality by using UV rays to kill harmful microbes.
But just how effective are UV lamps at eliminating harmful microbes? There are a lot of conflicting claims out there that make it hard to answer this question. As we look to extrapolate the truth from the marketing rhetoric, the first and most obvious place to start is with science.
What Is Ultraviolet Radiation?
UV light is a ray whose frequency falls just outside the higher end of the range of light on the electromagnetic spectrum, which is visible to the human eye. High-frequency rays like UV have shorter wavelengths than lower frequency visible light.
UV light is commonly understood to be comprised of three general sections, known as UVA, UVB, and UVC. While UVA is responsible for “black” light, UVB is the type that causes sunburn and skin cancers. With its shorter wavelength and higher frequency, UVC is the type of UV light that is used in UV lamps to eliminate microbes.
How Does UVC Kill Microbes?
The high energy contained in the photons which make up UVC rays is what gives them their potent anti-microbial properties. These photons play havoc with the DNA and RNA structures of microorganisms, causing enough damage to their genetic makeup to stop them from being able to reproduce.
So why, if UV rays given off by the Sun are constantly hitting the Earth, is our environment full of bacteria, viruses, and fungi that react negatively to or are killed by UV light?
The answer to this question is to do with a gas called ozone. Ozone is one of the most important gases that make up our planet’s atmosphere. It is most abundant in the stratosphere, where around 97 percent of the total amount of ozone present on Earth is concentrated. Among its numerous properties, ozone is extremely effective at absorbing UVC, meaning that next to no UVC rays end up filtering down to the surface of the Earth. Not only is the abundance of ozone in our atmosphere a good thing for microorganisms, but it is also a life-saver for us humans since UVC light is even more harmful to us than the UVB rays that many of us get acquainted with beach vacations.
How UV Lamps Work
UV lamps produce UV light by passing an electric current through a small amount of mercury, which is contained within the surface of the lamp tube. When electrified, the mercury reacts in such a way that it causes the lamp tube to evacuate to at pressure, which causes it to emit ultraviolet germicidal irradiation (UVGI), which has a wavelength of about 254nm.
As the name suggests, UVGI is effective at killing germs. This is especially effective at killing viruses that can accumulate within air-conditioning units themselves, although certain types of bacteria and fungi can have some resistance to it.
UVC lamps are usually hidden away in a separate air-cleaning unit or built into HVAC systems due to the fact that their rays also have harmful effects on human cells.
The Downside of UV Lamps
While UV lamps in air-conditioning systems can kill microbes that settle on the interior surfaces of the actual unit, the air in the system is usually moving at high speed, preventing the UV rays from having enough time to have much of an effect on airborne germs.
Another drawback of many mercury vapor UV lamps is that, in addition to outputting UV light with a wavelength of 254nm, they also produce a range of lower spectrum UV light with wavelengths of as long as 185nm. As well as having next to no germicidal properties, these longer wavelengths also have a nasty corollary effect; they convert oxygen (O2) into ozone (O3).
While ozone – as mentioned before – is a vital component of the Earth’s atmosphere, which allows life to thrive in the absence of harmful solar rays, the gas is toxic for humans and animals to breathe in when it is found on the Earth’s surface.
Not all lamps generate ozone, however. Look for UV lamps whose tubes are impregnated with titanium, a metal that prevents the passage of the lower-spectrum light, which causes oxygen to convert into ozone.
The Low-Down on UV Lamps at Home
When it comes to deciding whether to invest in a UV lamp at home, be aware of the following things:
- UV lamps in air-conditioning systems are very effective at killing germs that build up in the interior of the units themselves (particularly around the coils).
- UV lamps are not so good at killing germs that are present in the air that passes through an air-conditioning unit.
- If you are to install a UV lamp, make sure that it is one that features a tube that is impregnated with titanium to prevent it from producing toxic ozone gases.
Remember that before you purchase a UV lamp, it is advisable to take measures to improve the general air circulation in your house by opening windows and doors. For those people who are still concerned about the quality of the air in their residence after doing this, however, UV lamps can make a difference. Be aware, though, that many UV lamp companies will market their products in a way that makes them seem more effective at killing microbes in the air than they actually are.
Call Air & Energy of NWFL today to arrange a free quote.
This article was written by:
Nathan Noa
Co-Founder & Home Comfort Specialist