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The information below is extracted from the research paper: "Fluence (UV Dose) Required for up to 99% disinfection from Viruses, Bacteria, Protozoa and Algae"  that can be downloaded also on our website at the links below:

PDF: Fluence (UV Dose) Required to Achieve Incremental Log Inactivation of Bacteria, Protozoa, Viruses and Algae

Germicidal action of UV radiation

The effectiveness of sterilization or disinfection with UV light depends on the exposure, time, wavelength and irradiance.

• Exposure or fluence (sometimes called dose) is measured in mJ/cm² (where 1 mJ/cm² = 10 J/m²)
• Exposure time is measured in seconds (s), minutes (m) or hours (h)
• Irradiance is the flux of radiant energy per unit area, in other words how much of the UV radiation power (measured in W = 1000 “miliwatts” mW = 1.000.000,00 “microwatts” μW ) reaches the surface. Irradiance is measured in mW/cm² or W/m² (1 mW/cm² = 10 W/m²) and is dependent on the radiant power, distance and dispersion of the radiation emitted by the lamp source.

Many studies that show the effectiveness of UV light in disinfection or sterilization present in their findings the inactivation of virus or bacteria for a given Exposure in an amount of time, for a given UV wavelength. However, it is difficult to centralize or build a database with so many variables. The most common solution to this problem is to present the fluence required to achieve a log reduction from 1 to 5.

 Log reduction explained

"Log reduction" is a mathematical term (as is "log increase") used to show the relative number of live microbes eliminated from a surface by disinfecting.  For example, a "5-log reduction" means lowering the number of microorganisms by 100,000-fold, that is, if a surface has 100,000 pathogenic microbes on it, a 5-log reduction would reduce the number of microorganisms to one, equal to 99.999% kill rate.

This article is intended as a guide for those who are considering purchasing UVC disinfection equipment. These tips should only be considered as suggestions.

Attention buyers! - There are few recognized standards for equipment designed for UVC disinfection of air and/or surfaces. As a result, there are many advertisements and promotions claiming amazing performance with little or no scientific support.

• Ask the seller for copies of scientific papers that prove that his device actually works as he claims. The scientific work(s) should show the actual reduction of a test micro-organism in the environment in which the device is intended to work. 

• Does the product have suitable built-in UV safety sensors for automatic shutdown or does safe operation depend entirely on the operator?
• Does the device comply with NIOSH, UL, IEEE and related safety standards in the country of sale?
• Does the unit emit/generate ozone? If so, does it meet NIOSH requirements. How is the ozone attenuated? (We recommend avoiding ozone equipment, as it poses a safety risk to operators, unless ozone is specifically part of the treatment process and is used in a controlled and safe manner)?
• Is the device used to disinfect medical devices? If so, is it compliant with the requirements of the regulatory body in the EU, USA or country of sale?

• If the device is a UV rod that is used to disinfect a surface (e.g. a worktop or an envelope)

The technical specifications should state the UVC irradiance at a fixed distance from the UV front of the device (e.g. 10 mW/cm² at 2 cm).

The UV dose (irradiance multiplied by exposure time in seconds) should be at least 20-40 mJ/cm² to inactivate viruses on perfectly flat and ideal surfaces (details in this article). Thus, if the irradiance at the target surface is 10 mW/cm², the exposure time should be 2-4 seconds. However, the presence of microscopic gaps on flat surfaces can inhibit disinfection, and disinfection on other materials, such as cloths, may require completely different doses. For example, disinfection of viruses on medical masks may require doses as high as 1000 mJ/cm^2. This is a subject that is currently being researched and our current understanding changes almost daily.

With any UV device, you must NOT look at the UV light or expose your hands from the UV side. UV light is a source of skin burns/cancer and can quickly damage the eyes.

Remember that UV disinfection is based on a "line of sight" between the UV lamp and the target surface. If the UV rays are shaded by texture elements on the surface, the shaded areas may receive much less UV light or no light at all. Disinfection effectiveness is therefore determined by the UV dose to which these areas are exposed.

Like any disinfection system, UVC equipment must be used properly to be safe.

They all generate different amounts of UVC light in wavelengths from 200 - 280 nm. UVC light is much more energetic than normal sunlight and can cause a severe, sunburn-like reaction on your skin and could also damage the retina of your eye when exposed.
Some devices also produce ozone as part of their cycle, others produce light and heat like an arc welder, and still others move during their cycles. In general, all disinfection devices must therefore take into account the safety of both man and machine.

These considerations should be taken into account in the operating manual, in user training and in compliance with appropriate safety regulations.

Effective and cost efficient disinfection or sterilizing of surfaces, water and objects has become of huge importance. The current COVID-19 (coronavirus) pandemic made this extremely clear. It created a extreme buying spree for everything that can be used in fighting it.  Never before seen shortages of disinfectants, surgical masks, gloves, ventilators and more, happen all across the globe.

The situation is made worse by the fact that many of the materials used for sterilisation are single use and have to be disposed afterwards. More have to constantly produced, exacerbating supply issues. It is time for a more efficient way of killing virus and bacteria, it is time for disinfection with UV light.

Using ultraviolet (UV) light to disinfect or sterilize¹ has actually been embraced by some hospitals since years, by using large, industrial-grade machines to kill microorganisms (including COVID-19) in hospital rooms or on furniture, objects, clothing or instruments. However, such machines are prohibitively expensive for private or business use, as a mobile platform with UV lamps can cost more than 60.000 USD². They are also dangerous for people and have to be used only in empty rooms.

With the current advance in UV LED lighting technology, smaller versions of safe to use UV disinfection lamps can now be available to consumers and companies looking to clean pretty much everything, from office spaces, elevators and living rooms, to phones, computers and even toilet seats.

Widespread use of UV light to fight virus and bacteria can now happen with the technology of continuous disinfection with low intensity UVA light from lighting emitting diodes (LEDs).

Growing plants under artificial lighting in closed and fully controlled environments is a method of growing use and global impact.

Industrial scale indoor agriculture could become the main factor that keeps at bay famine and related conflicts. With increasing population, diminishing area of agricultural land, pollution, global warming and migration to grow plants in a reliable, predictable and efficient way will become even more important in the future.

Basic science concepts related to Horticulture lighting

A key factor in the success of indoor plant growth is the efficiency of the lighting system in the process of inducing plant growth, compared with sunlight. 

To build a very efficient lighting system some basic scientific concepts should be known.

Plants grow via a process called Photosynthesis that converts electromagnetic radiation – light – into chemical energy used for growth and development. The other ingredients needed are carbon dioxide (CO2), nutrients and water. The process itself is not particularly efficient, with only 4 to 6 percent of the absorbed radiation converted into chemical energy, but this is the engine that drives most life on the planet.

Photosynthesis and PAR radiation

The electromagnetic radiation required for Photosynthesis is defined as Photosynthetically active radiation (PAR), with the spectral range of 400 to 700 nanometers. Only radiation in the above interval can be used by photosynthetic organisms in the process of photosynthesis, to fix the carbon in CO2 into carbohydrates.

We should note that the electromagnetic radiation called visible light or simply light for a typical human eye has a spectral range from about 380 to 740 nanometers.

A common unit of measurement for Photosynthetically active radiation PAR is the photosynthetic photon flux (PPF), measured in units of moles per second. For many practical applications this unit is extended to PPFD, units of moles per second per square meter.

Growing plants in closed and fully controlled environments, under artificial lighting is method of growing popularity. There is also increasing competition to have results at a low cost and as fast as possible, thus the lighting system plays a crucial role.

Below you will find a quick guide how to build the most efficient lighting system.

1) Research, research

Understand what spectrum and intensity of light your plants need.

You can start by reading our detailed article about horticulture lighting here

2) Choose the right PPFD and light color for your plants

With the latest technology achievements, special or full spectrum white light LEDs are the most efficient and cost effective light sources for plant growth. With 3000K white color temperature you will have more pleasant looking plants while with 5000K you obtain faster growth.

With our Nichia 757 Rsp0a LEDs with white light for special spectrum for plant growth or full spectrum Nichia Optisolis CRI98 LEDs your plants will grow up to 50% more than conventional light, including standard white LEDs, a combination of red and blue LEDs or a fluorescent tube, for lower energy consumption.

According to the standard EN 12464 Light and lighting - Lighting of workplaces -Indoor work places, the light level recommended for office work is the range 500 - 1000 lux - depending on activity. For precision and detailed works the light level may even approach 1500 - 2000 lux. For ambient lighting the minimum illuminance is 50 ulx for walls and 30 lux for ceilings.

Recommended light levels for different types of work spaces are indicated below:

Read more about recommended lighting levels for the home in our blog article.

The light ceiling or illuminated stretch ceiling is a new and very interesting trend in interior lighting. By using a translucent material of many square meters in size with a backlight system a diffuse, uniform and relaxing illumination of interior space can be created. The main advantage of this type of lighting is the absence of glare, as the light sources are spread over a large area and hidden behind the material.  

Illuminated ceilings usually use as the backlighting source LEDs of low or medium brightness (5 to 50 lumens) placed on strips or modules.  As the illuminated surface has a wide area such low power lighting is the best choice. 

Illuminated stretch ceilings can have personalized shapes and even can feature translucent images. Such, they can influence the overall design of a space much more than other lighting fixtures. From the lighting design point of view the uniform light should be complemented with spotlights or lamps that could attract attention to certain areas or objects.

Properly designing and installing an illuminated ceiling has a unique set of challenges which we will address in this article. 

A new trend in lighting is the line of light, made with an LED strip inside an aluminum profile with translucent white cover. Such a linear light fixture can be many meters long, form geometric shapes, and is a type of direct lighting.

Compared with indirect cove lighting, also a popular trend in lighting design, lines of light are more energy efficient but can have greatly increased glare. For this reason direct lighting with lines of light should be designed with care and almost always be dimmable. 

Let's see how we can achieve the best results with lines of light.