Ultraviolet against a Second Wave - An easy to understand guide from Integration Technology
A simple and easy to understand guide to Ultraviolet (UV) and how it can help us halt a second wave of Covid 19?
The Virus examples that have been looked at are mainly based on SARS CoV-2 more commonly known as Covid-19, which is currently the center of attention, but they will also help us to understand the facts for other pathogens such as viruses, bacteria , fungi and algae.
What do we mean by UV?
The wavelength (expressed in nm for nano-meter) characterizes the type of light (it’s colour for example), our eye is sensitive to the range from 400nm to 700nm which represents ‘visible light’, it goes from purple to red. A Rainbow is a perfect example of the colour palette that our eye is able to see.
UV light is between 200nm and 400nm and is normally divided into three categories: UVA (400 - 315 nm), UVB (315 - 280 nm), UVC (280 - 200 nm).
The sun produces all three categories of UV. However, the ozone layer in the atmosphere absorbs the vast majority of UVB and UVC rays. At ground level there is almost only UVA left.
UV-C is harmful. Living beings are not naturally exposed to this wavelength of light, because most of it is absorbed by our atmosphere and it’s ozone layer, so have never developed systems to protect themselves from it.
UV rays are known to be harmful to the skin and eyes, which is why we protect ourselves by putting on sunscreen and wearing sunglasses. In reality UV is harmful to all living things, from microrganisms (viruses) to humans.
What are the sources of UV?
Besides the sun, many sources of artificial UV exist: the three main types are lasers, lamps, and LEDs. In our article we will focus on the last two, lasers typically have a point source and therefore are not suitable for decontaminating surfaces. In general, the main differences between LEDs and lamps in the UVC are summarized below:
In UVC the interest of LEDs will be limited to making small compact systems, where the lamps are too bulky. The lamps are more powerful, last longer and are cheaper. This is why for the vast majority of applications where UVC is required, lamps are preferred.
But with equivalent spectrum (UVC for example) all UV lamps are not equal and to know if a lamp is going to be effective two important parameters must be taken into consideration.
Power: Often expressed in mW / cm², it quantifies the intensity of light emitted during 1 second. Or is ‘how bright the light is’.
Quantity: If an object moves under a lamp, the slower it goes or the higher the power the greater the exposure to UV Light.
It is this quantity of light received, called the "dose" that allows us to compare different solutions. It is expressed in mJ / cm² (J = Joules) and we calculate it as follows:
Dose = Power per unit area (mW/cm²) x Exposure time
UV against micro-organisms
At the end of the 19th century, it was discovered that UV light deactivated micro-organisms and that the most effective wavelength is in UVC around 254 nm. UVC interferes with and destroys the nucleic acids, DNA or RNA of bacteria, viruses or other micro-organisms. The micro-organisms can no longer reproduce and become inactive.
Over the next century many applications developed, the main and best known being the decontamination of drinking water. In 2006 the ANSES (National Agency for Health, Environment and Work Safety) recalls reported the effectiveness of this technology .
What about the UV facing Covid-19?
UVC has been used in the past to fight other coronaviruses like MERS and SARS and was used in the fight against the recent Ebola outbreak in West Africa. Furthermore it is expected to have the same effect on Covid 19. This is why UV light and in particular UVC is taking an increasingly important role in the fight against the Covid-19 alongside, social distancing, hand sanitizer gel and different PPE. … UV appears to be a quick fix to destroy the virus everywhere: for example on your mobile.
But there are several points to be aware of:
UVC is very effective against micro-organisms, but is also dangerous for humans, we are also an organism. UVC lamps should not be used if there is any exposed skin! The International Association of Ultraviolet (http://www.iuva.org/) , in a press release of April 24, 2020, strongly advises against its use on the human body. The WHO (World Health Organi-zation) is even organizing an awareness campaign against the use of UV lamps to sterilize hands or skin.
Numerous offers for UV lamps to sterilize air, objects and surfaces are flourishing on the Internet. As discussed above, the majority of these solutions can be dangerous and do not reach the required UVC dose in the time suggested, so not deactivating the virus!
Covid-19 lifespan
A study of April 16, 2020 [4] published by the New England Journal of Medicine investigates the viability of Covid-19 in air and on various surfaces, established that the virus would be stable up to 72 hours on surfaces and 3 hours in the air.
This study also indicated that aerosol (air) transmission of Covid-19 is possible, as it remains active for several hours in air.
UV therefore is a solution for decontaminating both surfaces and air.
What UV dose is required?
The dose required to deactivate different viruses and bacteria in water is very well known and is noted in a 2005 review [2]. Note that the dose will deactivate a certain percentage of virus, more dose by increasing the dwell time, means a higher percentage of deactivation.
• However, there have been no published studies specifically carried out on the Covid-19 virus, but some elements can be used to estimate the necessary dose:
• Covid-19 contains single-stranded RNA and studies have shown that viruses with single-stranded RNA are 6 times more sensitive to UV than those with double-stranded RNA.
• Covid-19 has a diameter of 0.05-0.2 micrometers and a virus of 0.1 micrometers in diameter, it takes 10 mJ / cm² to deactivate it [3].
• A coronavirus requires 6mJ / cm² in air with low humidity to be 90% deactivated.
What possible applications for this exist for UV versus Covid ?
Many emergency services are equipped with portable devices in order to be able to quickly decontaminate the surfaces between two interventions.
UV lamp acts as a sanitiser in Emenrgency vehicles
Marseille firefighters have also recently equipped themselves with around twenty UV lamps to intervene in highly contaminated areas.
Image : https://www.integrationtechnology.com/en/contact/
Shanghai buses
The Shanghai public transport company has converted a washing station by in-tegrating 120 UV lamps to disinfect its buses. This new process allows them to reduce the decontamination time from 40 minutes to 5 minutes.
Image : http://french.china.org.cn/travel/txt/2020-03/05/content_75777884.htm
It can also be used in aircraft interiors and air traffic control towers.
Air decontamination
Busy places are equipped with devices to quickly and effectively decontaminate the air. Ideal for open spaces, restaurants, hotels, these air decontamination devices allow the recovery and destruction of possibly contaminated aerosols.
Image : https://www.ist-uv.fr/fr/applications/sterilisation/disinfection/sterilisation-de-lair
This article may seem a bit overly technical, but it is fundamental as it allows us to understand what UV is all about? We hope it makes it possible to better understand the full scope that UVC applications can offer against the Covid-19 virus and in particular it’s clear benefits to help us prevent and control a potential second wave.
However, we do recommend that you must remain vigilant about the use of UV and of course, to use validated systems whose effectiveness can be proven!
Depending on what you want to decontaminate, at what speed and for a given reduction it is necessary to be advised by professionals who understand the subject of UV decontamination.
Thanks and hope you find the information useful. And thanks to http://ist-uv.fr/ for the orginal article.
Check out www.uvintegration.com , http://ist-uv.fr/ or https://www.ist-uv.com/en/ for more information