The global pandemic has brought new advances in the century-old technology: UVC light to disinfect viruses and bacteria. Numerous peer-reviewed studies on UVC light show it’s effective against pathogens.
This is an overview of how UV works to kill germs, specifically on surfaces and in the air. We will also cover how you can tell it’s doing its job properly. While each UV application will have its nuances, these are the key things you need to know:
- Use a real UVC light source, not UVA, UVB, or just a blue or purple light
- Ask the manufacturer for specs about the UVC intensity or lab tests and results
- Make sure you’re using it safely – it’s not worth injuring yourself trying to kill germs!
- Understand how UVC’s effectiveness is based on power, distance, and time
- Consider which UVC device is best for your desired application and outcome
- Be aware of UVC’s limits – it won’t clean off dirt and works in line of sight so clean beforehand and reduce shadowed areas
- Use disposable dosimeters or invest in a reusable electronic one to measure the effectiveness
Keep reading to learn more.
Avoid the wrong type of UV light
Ultraviolet light is naturally emitted from the sun and has three types (or wavelengths):
UV-C from 200nm (nanometers) to 280nm,
UV-B from 280nm to 315nm, and
UV-A from 325nm to 400nm.
You only want to use UVC against viruses and bacteria, since UVA and UVB aren’t nearly as effective.
What’s the difference?
UV-A and UV-B are the wavelengths that pass through our atmosphere; UV-A causing sun tanning and UV-B, sun burning. Our ozone layer stops UV-C from reaching us on earth. This is good news for us because UV-C is absorbed by DNA, so it is harmful to our skin and eyes.
However, using UVC technology, we can use its germicidal properties to our advantage to inactivate bacteria and viruses. UV-C radiation disrupts their DNA and makes them unable to replicate and multiply. If a cell is unable to multiply and reproduce to infect a host, it is considered dead.
This is why UV methods of disinfection are called ultraviolet germicidal irradiation (UVGI): it reduces the number of viable microorganisms by deactivating them, whether it is applied to water, air, or surfaces.
Make sure to use genuine UVC light
Uninformed retailers may not know the difference between UVA, UVB, UVC or just regular blue lights. Some are knowingly scamming. Therefore, you should only buy from reputable sources.
UVC light is more than a blue light
When most people think of ultraviolet light or UV disinfection, they think of the bright purple or blue lights emitted from these devices. But UVC is at a lower wavelength, so it is invisible to human eyes.
That glowing blue light you see is an indicator that the UVC light is receiving power and working. Even if the light appears to be working, always do your due diligence to make sure it is UVC.
The lamp may still glow even if it is no longer emitting UVC. On average, 254nm UVC tube lights should be changed every 8,000 hours, UVC LEDs every 10,000 hours, and Far UV lamps every 6,000 hours. Ask the supplier for the specifications for the device you’re interested in.
Consult with the manufacturer or seller
To best find out if the UVC lamp you are looking to purchase is real, vet whoever is selling the device. If they’re legitimate and knowledgeable, they should be able to answer some key questions about UVC and the device itself.
Ask about the wavelength of the light
It should be either 254nm or 260-280nm. Far UVC lights are rare, but they emit light at 222nm. Anything greater than 280nm is veering into UVB and UVA territory which do not have the same germicidal properties as UVC. Blue light is between 450 and 495nm, so this is not in UVC’s range either.
Ask if they have specifications about the device’s UV light intensity
UV light intensity is measured in µW/cm² (micro-watt per square centimeter). The seller will also specify at which distance that intensity was measured. It is even better if they can provide a table with the test distances. The further from the lamp, the lower the light intensity will be. If they give you a light intensity measurement, also ask at what distance it is.
Ask about 3rd party lab tests
The seller should be able to give you some data on how well the light has performed against a specific virus or bacteria. The results will include the type of pathogen, level of inactivation as a percentage (usually 90%, 99%, 99.9% or 99.99%), and the UV dose needed. The UV dose will be in mJ/cm2 (millijoule per square centimeter) usually. You might also see an old measurement unit, mW-s/cm2 (milliwatt-second per square centimeter).
Because dose is based on time, there should be a measurement of time to achieve the dose as well. It is best if the test was done through a 3rd party, since they will try and achieve accurate and objective results.
Ask for a light meter or dosimeter reading
If the seller has inventory available, they should be able to take a photo or video of testing the device with a dosimeter. On the reading, there will be a spike of radiation in UVC’s 200-280nm range. You will likely see a spike in blue light 450-495nm range as well, due to the blue indicator light.
Test it yourself with a disposable dosimeter
Disposable dosimeters usually look like a card with a colour-changing indicator. The indicator will change depending on how much radiation is received. Not only will these confirm that your UVC light is real, but some will give you an accurate UV dose measurement.
Check for safety features
UVC is a powerful and effective tool to fight against viruses and bacteria, but it must be used safely. People and animals cannot let their skin be exposed or look at UVC light (even for a second!) otherwise they will be burned. Make sure there are no pets, animals, or plants in the room either.
For this reason, if working with a direct UVC light source, make sure it has the relevant safety features. Safety features to look out for include but are not limited: delay timers to let you leave the room before the light turns on, timer function, remote control operation, and an automatic shutoff motion sensor.
If you are planning to install UVC lights, it’s recommended to look into setting up an interlock system as well. UV Can’s Safe Space Interlock System has a main control switch, magnetic deactivation door switch, and lock with admin key to restrict access.
Make sure to wear proper PPE, such as clothes that completely cover your skin, and a face shield or goggles. It isn’t worth using a UVC device if you or others get injured in the process.
Some UVC devices have their light completely contained inside of a box or air purifier, with no leakage. This is usually specified in the product’s description. You can always ask the seller about whether there is light leakage, so you know what precautions to take.
Consider UV light sterilization time, distance, and power
A general rule of thumb is that the higher the power, closer the distance, and longer the time, the more effective the UVC light will be at destroying pathogens.
Watts are measured in W and are a unit of power. The higher the wattage of the lamp, the stronger its power. This is a key specification to consider for full-room surface disinfection.
The closer the lamp is to a surface, the more effective it will be. Some UVC lights are portable so you can run multiple disinfection cycles to cover different areas of the room.
UVC light needs time to work as well. The longer the disinfection cycle, the more effective it will be. It is a good idea to take a longer time rather than a shorter time.
Choose the appropriate device for your desired application and outcome
You will need to consider different measures of effectiveness depending on what you want to use UVC for. For example, if you are looking to sanitize your phone or mask, there are compact UV boxes such as Anemone. These don’t necessarily require a large amount of power or time to disinfect since the lights are close to your personal belonging’s surface.
Crocus handrail disinfectors are installed mere millimeters away from the surface of the moving handrail, so germs get zapped instantly as there is almost zero distance.
A disinfection machine like Lavender is best for large rooms, since it uses 1,600W of power. It should still be placed relatively close to the target disinfection surface, or the most effective spot in the room.
In many cases where distance is a challenge, multiple units may be necessary to achieve the best results. Devices like Verbena are designed to be strung along the ceiling of a factory or warehouse, with a power cord to connect them to each other.
Some UV devices will come with additional technology, such as fans or HEPA filters to increase their efficacy. The Carnation UVGI ceiling fixture emits UVC in a 6-meter radius above people’s heads. This creates a disinfection zone for airborne particles floating close to the ceiling. Carnation’s fan also sucks in air from the room below where people are breathing out viral particles, bringing them close to its UVC light source, then expelling the disinfected air into the room.
Know the limits of UVC
To use UVC well and effectively, it is important to know its limits and how to work with them. Depending on your desired application, some limits won’t be as relevant as others.
UVC’s main weakness is that it works in line of sight, so objects in the way of the light source will create shadowed areas. These areas won’t get the desired UV dose compared to areas in direct light. It’s not only large objects, such as a chair or table in the way, but even dust particles can shield viruses and bacteria.
This rule of thumb applies to porous surfaces as well, such as fabrics on furniture, blankets, untreated wood, carpets, etc. The UVC light will reach the microorganisms in sight but won’t penetrate the porous material.
There are some steps to take to reduce shadowed areas. Absolutely clear away any objects or clutter potentially blocking the UVC device. Clear away any dust or dirt in the area as well. You will also want to strategically place the UVC device and use multiple of them as needed.
There are high-powered devices such as Verbena meant to be installed at various points in problem areas. There are even autonomous UVC robots which will navigate the room to reduce shadowed areas. Porous surfaces should be cleaned according to instructions, but it doesn’t hurt to use UVC as one extra last step.
Avoid exposing people to UVC light
UVC is dangerous to skin and eyes, so only use it directly on surfaces while the space is unoccupied. Some households and businesses can easily navigate this, while others will find it challenging.
Some households will have time when everyone is at work or school. One could set the UVC disinfection as the last step before going out. Businesses often have an after-hours closing time where it would be safe to use the device.
Some households and industries do not have routine times where the space is unoccupied. There are applications that will contain the light to a designated space out of harm’s way, like the upper part of a room, or enclosed inside an HVAC duct or air purification unit. These devices are designed to be safely used even while people are in a room.
UVC light applications meant for occupied rooms are usually targeted towards airborne viruses and bacteria rather than surfaces. However, the latest innovation in UVC technology, 222nm Far UV, is safe at low doses of 3 mJ/cm2/hour.
Far UV lamps are hard to find right now, but they can be used to disinfect surfaces even while people are in the room. UV Can Sanitize supplies a range of Far UV devices for many different applications.
UV disinfection is based on time
Another factor to consider is that UV disinfection works best when given an adequate amount of time. This is another factor that may be a challenge to some individuals, households, and businesses, while others will be able to find a natural fit.
If time is a limitation for your desired application, you may be able to find a workaround by using a device with increased power, or at close range. Some UV devices such as Clematis are high-powered, mobile, and adjustable to disinfect their targeted surface in only 5 minutes.
Use a dosimeter to measure effectiveness
UV dosimeters are helpful when it comes to measuring UV exposure on surfaces, or to check if your device is authentic and working. There are a couple different types of dosimeters.
Disposable dosimeter cards are good when first installing a UV disinfection system, or to check if the device you just bought functions as needed. It might be good to even have a couple on hand to check the device at different points during its lifetime.
Some disposable dosimeters are only calibrated for certain UVC wavelengths, such as 254nm or 260-280nm. Make sure you are buying the right one beforehand for the most accurate result. Intellego Technologies has a wide selection. Disposable cards are single use only.
There are electronic dosimeters as well. These are more expensive but are reusable. Some are designed to be wall-mounted. If you have a specific surface that needs to get the right amount of exposure each time, these may be worth the investment.
There are also handheld UVC dosimeters where you place the sensor on your target surface. The unit will give you a reading of the detected wavelengths and dose received. These will also be more expensive, but you can reuse them as many times as needed.
It doesn’t hurt to ask the seller if they have any dosimeters in stock. You may be able to buy one from them along with your new UVC device.
UVC is a proven technology against viruses and bacteria. Now that you know how to tell if a UV sanitizer is working and effective, you can confidently browse and choose the right devices for you and your needs.
You can get a free consultation with UV Can’s industry experts about how to best incorporate UV into existing disinfection and sanitization routine. Either email firstname.lastname@example.org with the subject line, “Free Consultation” to start booking a time or call our office at 604-423-5599.