How UVC lights work for disinfection
How UVC lights work for disinfection
In order to understand the above, we 1st need to understand how all ultraviolet rays (UV lights) work.
The wavelength of 100~400 nm in the spectrum is ultraviolet (UV), between X and visible light. Ultraviolet light is divided into UVA, UVB, UVC, and UVD. according to wavelength.
Long-wave ultraviolet rays with wavelengths of 320~400 nanometers have the strongest penetration. These UVA ultraviolet rays coming from the sun can penetrate the ozone layer and clouds to the earth’s surface. UVA can reach the dermis of the skin, directly damage the cells, can tan your skin, age, and wrinkle it.
Midway UV, the wavelength at 280~320 nm mostly gets absorbed by the ozone layer. About 2%~10% of this reaches the ground. It promotes the body’s mineral metabolism and the formation of vitamin D.
Short wave UV, the wavelength at 200~280 nm is almost completely absorbed by the ozone layer. It has weak penetration ability and it does not penetrate glass and plastic products. The ultraviolet germicidal lamp uses UVC shortwave ultraviolet light. Although it has weak penetration, it is harmful to the human body.
Vacuum ultraviolet light, the wavelength at 100~200 nm, has very weak penetration abilities. It can oxidize oxygen in the air and convert it to ozone.
Now let’s talk about UVC lights
For sterilizing, UVC ultraviolet (mainly 240 nm ~280 nm) destroys the molecular structure of microbial cells DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Resulting in the death of growth cells and/or regenerative cells. Thus achieving the effect of sterilization. See a video of it in action.
Since typically this type of light is blocked from making it to earth, humans and living organisms can be harmed or killed by it. We don’t have immunity to it. This is also applicable to the novel coronavirus – covid-19. See more information about this on CDC website.
All coronaviruses are single-strand positive RNA viruses
How do ultraviolet disinfection and sterilization lamps radiate UVC ultraviolet rays?
At present, there are two main light sources of ultraviolet disinfection and sterilization lamp – gas discharge light source and solid-state light source.
The gas discharge source is mainly a low-pressure mercury lamp. The principle of luminescence is the same as that used in previous fluorescent lamps, which excite mercury atoms in lamp tubes. Low-pressure mercury vapor mainly produces 254 nm UVC ultraviolet (30%~60%) and 185 nm UVD ultraviolet (5% and 15%).
As mentioned above UVC UV sterilization is the most effective, but UV can only travel in a straight line, the penetration is weak, so there is a blocked disinfection dead angle. 185 Nano-UV UVD does not have a strong physical sterilization effect in itself, but it can decompose the oxygen in the air combined to produce ozone. Ozone has a strong oxidation effect, it can flow with the air to every corner and it has complete sterilization disinfection (biochemical oxidation sterilization). But excessive ozone concentration is harmful to the human body. This can be circumvented by opening doors and windows to ventilate after use.
The gas discharge light source also has a pulsed xenon lamp. It uses the heat shock and the partial ultraviolet ray to sterilize. The sterilization efficiency is higher than the low-pressure mercury lamp, but this technology is expensive for the little improvements it has.
How to Select Ultraviolet Lamps
This is recommended for home and office use. Most of them have timing, remote controls, and infrared sensing functions. These are safe and convenient.
Wall mounting type
Generally seen in factories, restaurants, warehouses, and daycares.
How much power (wattage) do you need?
As a rule of thumb, 1.5 watts per 35 sq ft.
For the tech guys, you can see this formula in cubic meters:
n ――Amount of UV-Vis Sterilizing Lamps Based on 30 w
h ―― Sterilization lamp to ceiling distance (m)
v ―― Room volume, cubic meters
f ―― 0.8 Lamp efficiency, generally take 0.8
Choice of ozone or ozone free
Ozone UVC lights are always the best. Because the ozone they produce will travel to every nook and cranny to deactivate. But, ozone may not be good in places, where humans have to occupy the space without prior ventilation. For example, a salon or a doctor’s office where new people enter the room every 15 minutes. If you find yourself in this position, then select the ozone free UVC bulb.
How long does sterilization take?
There is a lot of misinformation on this subject. So, we took an ATP meter, that measures microorganisms, and put it to use to see. Our conclusion was that it took 30 minutes to sanitize any surface that the light came in contact with.
How long does it take to kill the new coronavirus?
The CDC’s latest guidelines say “ultraviolet rays can inactivate the new coronavirus”, but they do not say how long it will take. No accurate experimental data are available to show how much ultraviolet radiation dose could kill the new coronavirus.
The Centers for Disease Control and Prevention (CDC) virus prevention and control experts in a 2003 study reported that UVC exposed to more than 90μW/cm² of intensity SARS coronavirus, which can kill SARS virus in 60 minutes.
SARS virus inactivation time is also only a side reference, after all, this new coronavirus is not SARS coronavirus, there is a correlation, but not the same.
UV radiation intensity and distance are also related, the farther away from the UV lamp, the bactericidal effect will be relatively weakened. According to the technical specification for disinfection issued by the Ministry of Health, the lifting height is 5 to 8 feet of ground, which makes the respiratory zone of human beings in the effective range of exposure.
How often do I change the lamp?
Without doing a test ATP meter, it can be hard to tell. A good rule of thumb is to replace it once a year for optimum performance.
How to Use – Safety Norms
First pay attention to the ambient temperature, too high or too low temperature will affect the intensity of ultraviolet radiation and then affect the bactericidal effect. The ultraviolet radiation intensity was the largest and the most stable at 68 to 104F at room temperature. As a result, temperatures below 68F or above 104F require an appropriate increase of time for UV exposure.
Best humidity disinfection occurs at a humidity of 55% to 60%. Ultraviolet radiation at this humidity kills bacteria the fastest. If the humidity exceeds 60%, the UV penetration will decrease, and the bactericidal effect will decrease by 20% to 30%. It’s best to use it when the humidity is in the above-mentioned range and in a sunny room.
Don’t look at the light-emitting lamp with the naked eye. And, don’t expose your skin to ultraviolet lights for a long time. During disinfection, doors and windows must be closed, people and pets must leave the disinfection site, and items such as plants and valuables should be removed or covered. Lights with radar control are available that will automatically turn off when it senses people near it.
If you have a large area to cover, like a large office or a hospital, there is no better cost-effective way of doing this than the UVC robot. The UVC robot has a built-in computer on it and it is programmed to go around in the building doing it’s sanitizing duties.
After disinfection, ventilate the area – open doors and windows. Finally, clean the tube with rubbing alcohol after it cools down.
I hope you enjoyed the article. Please comment below and let me know your thoughts.