LED Lighting Knowledge

Advice for the purchase and use of equipment for the UV disinfection of air and surfaces

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/cm2. 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.

Most popular types of LED Strips explained

Lighting systems named LED strips include a broad range of products such as flexible LED strips, rigid LED strip, Zhaga LED strip, backlight LED strip, power LED strip and much more. Lets briefly explain the most popular types.

Flexible LED strips

  Professional Lumiflex Nichia LED Strips, 100.000 hours lifetime, flux up to 2600 lm/m

Flexible LED strips are a string of LEDs on a narrow, flexible PCB. Other common names are "LED tape light" or "string light". They are usually delivered in lengths of 5 meters, in reels. Most LED strips work at 24VDC or 12VDC and one reel can light up at once from a compatible transformer.

To allow permanent installation, flexible strips require a surface that is well suited for the back adhesive tape they have on the back, such as one made from glass or metal. Aluminum profiles are ideal to use with flexible LED strips, as you they offer the necessary cooling and also convert the strip into a linear lighting fixture.

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Fluence (UV Dose) Required for up to 99% disinfection from Viruses, Bacteria, Protozoa and Algae

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 exposuretimewavelength 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/cmor 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.

Log Reductions from 1 to 5 are the most common in research papers about UV light disinfection. Their meaning:
  • 1 log reduction means the number of germs is 10 times smaller (101)
  • 2 log reduction means the number of germs is 100 times smaller (102)
  • 3 log reduction means the number of germs is 1000 times smaller(103)
  • 4 log reduction means the number of germs is 10,000 times smaller(104)
  • 5 log reduction means the number of germs is 100,000 times smaller(105)

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Disinfection with UV Light, >99% Kill Rate for Bacteria and Viruses (incl COVID-19)

UV light breakes the DNA of viruses and bacteria

   

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.

  "UV light annihilates viruses and bacteria by destroying their ability to reproduce. " 

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.

UV robot for hospital use

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).

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Horticulture LED lighting guide

Light for plant growthGrowing 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.

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Recommended light levels for office lighting

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

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:

ActivityIlluminance
(lx, lumen/m2)
Areas with traffic and corridors - stairways, escalators - lifts - storage spaces 100
Working areas where visual tasks are only occasionally performed 100 - 150
Warehouses, archives, loading bays 150
Coffee break room, technical facilities, ball-mill areas, pulp plants, waiting rooms 200
Easy office work 250
Normal office work, PC work, show rooms, laboratories, check-out areas, kitchens, auditoriums 500
Mechanical workshops, office landscapes 750
Normal drawing work, detailed mechanical workshops, operation theaters 1000
Detailed drawing work, very detailed mechanical works, electronic workshops, testing and adjustments 1500 - 2000
Performance of visual tasks of low contrast  and very small size for prolonged periods of time 2000 - 5000
Performance of very prolonged and exacting visual tasks  5000 - 10000
Performance of very special visual tasks of extremely low contrast and small size 10000 - 20000

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

Flexible LED strips for applications with high lux requirement

How to best build an illuminated stretch ceiling with LED modules

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 ceiling with LEDs, inside an office

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. 

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How to create lines of light or linear light fixtures with LED strips

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.

Line of Light with LED strip inside a profileCompared 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.

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Cove lighting with LED strips

A cove luminaire is a light line that can be made via an LED strip that is hidden within a Cove in the wall or ceiling that illuminates an adjacent surface. Light is reflected from this surface into the room to be illuminated. For this reason, light lines are generally referred to as cove or indirect lighting.

Cove lighting is a popular trend in lighting design, focusing on human nature and the behaviour of natural light. It is widely used today, with light lines as the main method of lighting interiors.

The attraction is the similarity with the natural light. With the right light source we could imagine that the bay is actually a hidden window to the outside from which the sunlight streams in.

Let's see how we can achieve the best results with cove lighting.

1. Use of energy-efficient light sources

Choose LED modules or strips with high energy efficiency, at least 100 lm/w, and place them within the coving light so that most of the emitted light uses the reflective surface, wall or ceiling that directs it into the interior. Waste of energy for lighting the interior of the bay should be avoided. LED strips with 120-180° are recommended, which should be placed at an angle if possible:

Surfaces that are more absorptive than reflective, like dark paint or wood should be avoided unless the design is primordial to energy efficiency. White ceilings produce the best results.

2. Select an LED light source with the correct light output.

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How to choose the light with the right CRI for your project

The Color Rendering Index or CRI, for short, is a one number quantification of how good (or bad) an artificial source is at reproducing colors, compared with reference standard illuminant modeled after daylight. The highest number is 100, for daylight and incandescent lamps/halogen lamps, while gas discharge lamps are between 17 and 96, with even a negative value for sodium low pressure (the yellow type used in street lamps).

It was introduced by the International Commission on Illumination (CIE) in 1974, because of the wide variation in the ability to reproduce colors with the white light emitted by the many types of gas-lamps then on the market.

Today, with over 40 years of use, the CRI index is firmly rooted in the lighting industry and among professionals. However, it has failed to gain much traction among the general public due to the fact that soon after its introduction it became not really relevant when making a purchase decision for lighting.

The reason was that most lamps were built for specific applications that required a minim CRI value so one could not go wrong with the choice of lamp.

From 2000s onward, LED technology changed this. It is the first lighting source that can be used for every application and have the full range of performance and quality level, including the ability to accurately reproduce colors. Therefore, it is imperative you choose the LEDs with the correct CRI level for your application. CRI comparison

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