Energy Resources

Frequently Asked Questions

How Does Germicidal UV-C Lighting work to inactivate viruses?

UV-C Light refers to a very specific part of the electromagnetic spectrum. This type of light is naturally blocked by the ozone, but over 100yrs ago scientists figured out how to harness this specific wavelength of light and use it to start disinfecting surfaces, air, and even water. For microorganisms that come into contact with this light, having never been exposed to this specific wavelength, it proves to be deadly by actually changing the RNA/DNA of the microorganism and removing the possibility of replication. In short, this is how “UVC light kills COVID-19”.

Are the air purifiers that VLED sells, recommended?

SAFETY – Germicidal UV-C lighting is harmful to humans and systems must be commissioned to ensure the safety of everyone. Site glasses, LED indicator lights, time clocks, motion sensors, and other controls are often used in conjunction to ensure the safety of building occupants, maintainers, and operators of the equipment. Please review manufacturer instructions and safety manuals before operating or installing GUV systems.

Application – Germicidal lighting can be used on surfaces, on air, or on water. it is important to understand the different application types and efficacy of the system designed for each application. VLED currently does not offer systems to remove pathogens in water.

Wavelength – Most of the products VLED may specify in projects are low pressure mercury vapor (LPMV) lamps. These lamps produce light at the 254.7nm wavelength. Recently released studies such as the one from Signify out of Boston University, confirms inactivation of SARS-COV-2, in a controlled environment, at this wavelength. Other light source types may reach different wavelengths or ranges, so it is imperative to confirm the wavelength by reading manufacturer specification sheets.

Studies by Dr. David Brenner at Columbia University, have confirmed a lesser known wavelength called Far-UVC (222nm), inactivates coronavirus-like viruses (and preliminary results suggest it can inactivate SARS-COV-2 as well). The larger benefit to this revelation is that Dr. Brenner has also proved that ultraviolet light at this wavelength CANNOT penetrate the dead cell layers on the skin or the cornea of our eyes. As of 08/16/2020, VLED is unaware of any FDA approval for the utilization of this lighting technology in occupied rooms. Studies are ongoing, but preliminary results are promising.

Far-UVC light doesn’t really discriminate between coronavirus types, so we expected that it would kill SARS-CoV-2 in just the same way,” Brenner says. “Since SARS-CoV-2 is largely spread via droplets and aerosols that are coughed and sneezed into the air, it’s important to have a tool that can safely inactivate the virus while it’s in the air, particularly while people are around.”

“Because it’s safe to use in occupied spaces like hospitals, buses, planes, trains, train stations, schools, restaurants, offices, theaters, gyms, and anywhere that people gather indoors, far-UVC light could be used in combination with other measures, like wearing face masks and washing hands, to limit the transmission of SARS-CoV-2 and other viruses.”

Light Source and Degradation – Light levels degrade over time, and different types of lighting produce ultraviolet light at different wavelengths, as discussed above. A brand new LPMV lamp has about a 1yr lifespan (or 10,000hrs) rating. At this time the bulb will either fail or reach an unacceptable degradation and reduced intensity. It is important to understand the difference between different lighting types and replacement schedules.

Irradiance (Intensity) – Expressed in watts (W), milliwatts (mW), or microwatts (μW) per square centimeter (cm2). Recommended 30 μW/cm2 to 50 μW/cm2 for Upper Area UV-C, and 10 μW/cm2 to 20 μW/cm2 for surface disinfection.

• Total radiant power of (all) wavelengths passing from all incident directions onto an infinitely small area

The higher the wattage of bulbs, the more intense the Germicidal UV-C light is. Intensity is linear to time of exposure needed to inactivate viruses. For example, ambulances use a very high powered Germicidal UV-C fixture because they need the ambulance to be disinfected very quickly to avoid downtime and maintain emergency readiness, whereas an office may use a less intense solution because spaces remain unoccupied for longer durations and disinfection time is not necessarily of the essence.

Distance – Germicidal UV-C lighting uses shortwave (200-280nm wavelengths) irradiance to inactivate viruses by restructuring the DNA/RNA and removing possibility of replication. The further away the light source is from the infected surface or air, the less effective the inactivation will be. To combat this, exposure time may be increased, numerous fixtures may be specified to stage multiple irradiance fields in the most effective manner, based on all the variables listed within this FAQ section.

Exposure – Viruses are inactivated based on the amount of exposure they have in the irradiance field. Depending on the application (surface or air), the intended area or space for virus inactivation may need a certain amount of exposure time to reach the needed level of dosage.

Radiant Energy (Density) – Expressed in joules (J) or millijoules (mJ) per square centimeter (cm2). One watt for One second = One joule dA. (Incorporates time as part of the measurement and is the area under the irradiance curve.). This is often the only UV exposure guide number supplied on the specification sheet.

The density of Germicidal UV-C lighting to a specific surface is mostly commonly measured in millijoules per centimeter squared. The Boston University study referenced above inactivated 99.99% of SARS-COV-2 at 5mj/cm2 in 6 seconds.

Dosimeter – Commonly known as “indicator strips”, dosimeter strips can detect the dosage amount received on a given area. This is how a user of Germicidal UV-C light can determine whether an area has received the correct dosage. A commonly approved dosage amount for surface area disinfection is 20mj/cm2. 5mJ/cm2, resulting in a 99% reduction of the SARS-CoV-2 virus in just six seconds (controlled environment, other variables considered). A method for the measurement of monochromatic low pressure mercury vapor lamps can be found here.

Shadowing – Germicidal UV-C lighting is only effective on surfaces and air that pass through the irradiance field of an active light source. Shadows determine no light is hitting that surface, and therefor disinfection is not happening. To overcome this issue, reposition the lighting, or use a handheld UV-C device where you can access the shadowed area.

Humidity – ASHRAE recommends 40-60% humidity levels. An increase in humidity may cause large water droplets to form and impede the effect of the germicidal UV-C light.

Air Mixing – This is particularly important when looking to design an Upper Room Germicidal UV-C system. The CDC (NIOSH) refers to this as UVGI (Ultraviolet Germicidal Irradiation). In March 2009, the Department of Health and Human Services,

Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, published these guidelines on the installation of Upper Area Germicidal UV-C systems, specifically for the fight against M. Tuberculosis.

How do filters play a part in indoor air quality?

HEPA – “HEPA” stands for High Efficiency Particulate Air. Every HEPA filter must have an efficiency of 99.97%, meaning if 10,000 particulates, at 0.3 micron size, pass through a HEPA filter, only 3 may escape. For context, one micron equals one twenty five thousandth of an inch. Filter and product manufacturers must receive third party testing through the Institute of Environmental Sciences and Technology, to hold the HEPA Rating.

MERV – “MERV” stands for Minimum Efficiency Reporting Value. This standard of testing and reporting was developed by the American Society of Heating and Refrigeration Engineers, better known as ASHRAE, and subsequently adopted by the International Standardization Organization (ISO), to standardize the reporting of the efficiency of filters across the community. MERV values range from 1 – 16, with 16 being the highest efficiency rating possible on this scale. As of 08/16/2020, ASHRAE recommends MERV 13 or higher, when possible.

Replacement – ASHRAE states, “Filters in HVAC systems should be changed according to the typical schedule or even left in place longer than normal. Extending the time between filter changes is a strategy being employed during the current COVID-19 pandemic. If lower rated filters were upgraded to meet ASHRAE recommendations of at least a MERV 13 filter, there was likely an increase in airflow resistance (increased pressure drop) when the new filters were installed.  However, the upgraded filters may be capable of holding more dust than the lower rated filters without a substantial additional increase in air flow resistance.  Thus, extending the time between filter changes may be beneficial.  Either way, the risks from not changing filters right on time are small.  The filters may load more than normal, which could lead to slight reductions in air flow.  The secondary impact of that depends on the type of building and building occupancy (among others).”

***VLED would like to add, if Germicidal UV-C lighting is being used in or around filters, as such with our Coil Scrubber, we recommend changing your filters every 90 days, to reduce the chance of filter material breaking down due to long term exposure to ultraviolet light. It is recommended that you consult a licensed and insured HVAC company, technician, or engineer, when determining the options of filter replacements and the retro-commissioning of your system in response to COVID19. Increased filtration typically requires filters be replaced and changed more often, a decrease in air flow, and an increase in power needed by the HVAC system to push air through the given stages of filtration. These are just some of the variables to consider.***

How can you reduce viruses from being transmitted through the air?

  • Supply clean air to susceptible occupants
  • Contain contaminated air and/or exhaust it to the outdoors
  • Dilute the air in a space with cleaner air from outdoors and/or filter the air
  • Clean the air within the room

Helpful Links









Mention of any company or product outside of the VLED organization does not constitute endorsement by VLED. In addition, citations to Web sites external to VLED do not constitute endorsement of the sponsoring organizations or their programs or products. Furthermore, VLED is not responsible for the content of these Web sites.

There are no claims in any of our products offerings that include the ability to destroy, repel, trap or mitigate (lessen the severity of) any pest such as insects, weeds, rodents, certain other animals, birds, mold/mildew, bacteria and viruses unless otherwise expressed with supporting documentation. VLED simply refers to facts based upon history and peer reviewed, commonly accepted, independent studies.

Commercial LED Lighting FAQs

What is included in a proposal?

  • Manufacturer Specification Sheets
  • Bill of Materials & Lighting Schedule
  • Fixture Layout with Red-Lined As-Built Drawings
  • Foot-candle & Photo-metrics
  • Energy and Environmental Study – ESG / SRI / EH&S Reporting
  • Finance Package w/ Executive Summary

Do I qualify for rebates or other incentives?

This is determined on a case by case basis, given the requirements of each program. Over 80% of all lighting projects we complete are off-set by financial incentives.


What is the average Return on Investment?

Depending on a number of variables, the average ROI of a LED lighting retro-fit is 2-3yrs.

How is my savings calculated?

Each site is calculated separately based on the hours of operation, kWh rate, ballast factor, lifecycle cost, maintenance costs, cost of capital, etc.

Do you guarantee the savings?

Our Lighting-As-A-Service model guarantees the savings and finances the the projects and services costs over 3-7yrs.


How long do LED’s last?

(Excluding screw in bulbs) LED lighting fixtures last roughly 5-10yrs. There are fixtures and lamps that are rated to last longer, but it varies. When considering the lifespan of a fixture or lamp, look for the “Rated Hours” listed on the specification sheet. This is one of many data points you should investigate, but pay close attention to the adjacent words “LM70 or LM80”. LM70 is a light fixture measured at 70% its original output, LM80 at 80% its original output. The effectiveness of a fixture is measured by the lumen output and degradation over time. Therefor you will usually see something like this: “Rated – 50,000hrs @ LM80” See VLED Minimum Warranty Here

Does LED Lighting put off less heat?

Yes, LED lighting puts off less heat that conventional lighting such as incandescent, fluorescent, metal halide, HPS, etc. That being said, every power source puts off heat. In theory, because of this ability of LED’s, HVAC savings can be captured depending on the environment and existing fixtures. Heat sinks and heat dissipation are particularly important when researching the correct lighting fixture, especially when designing a retro-fit kit to fit inside an existing light fixture housing.

Why does LED lighting fail?

LED lighting usually fails due to inadequate power sources or poor manufacturing. LED drivers swap the power source from alternating current (AC) to direct current (DC). DC current is required by all led diodes and solid state lighting. Drivers are becoming increasingly more reliable each year. There are also manufacturers who are offering “driver on board” or “driverless” technologies. A lifecycle costing analysis should be conducted when considering the “driverless” option, along with due diligence on the manufacturers warranty process.


Lighting and Controls Acronym Index

  • LED – Light Emitting Diode
  • UL – Underwriters Laboratory
  • DLC – Design Lighting Consortium
  • LaaS – Lighting-As-A-Service
  • PoE – Power Over Ethernet
  • ESPC – Energy Saving Performance Contract
  • PPFD – Photosynthetic Photon Flux Density
  • PPF – Photosynthetic Photon Flux
  • PAR – Photosynthetically Active Radiation
  • DLI – Daily Light Integral
  • FC – Foot-candle
  • IP – Ingress Protection
  • LRV – Light Reflectance Value
  • UVC – Ultraviolet-C Wavelength