What is UV light?
UV light is produced naturally by the sun. It is also produced artificially for use in medical, commercial and industrial applications.
Sunlight contains three types of UV light, all of which are invisible to the human eye. UV light is divided into three bands or waves:
- UVA, also known as “low energy” or long-wave, from 315 to 400nm
- UVB, also known as “medium energy” or medium-wave, from 280 to 315 nm
- UVC, also known as “high energy” or short-wave, from 100 to 280nm.
UVA and UVB rays can damage the DNA in our skin and tissues. Both UVA and UVB can be blocked by sunglasses and sunscreen.
UVC light is less well known. Most naturally produced UVC light is filtered out by the atmosphere before it hits our skin or eyes.
Does UVC light destroy germs such as bacteria and viruses?
Germs are harmful microscopic bacteria that cause diseases and infections. Germs thrive when they find an environment where they can live and reproduce, such as water, air, on a body or in air.
Bacteria are single-celled microorganisms. Viruses are smaller than bacteria, but they require a living cell to host them. Once they find a host cell, they destroy it and spread to adjacent cells. As they multiply, they make the host sick. Viruses cannot live long outside other living cells.
The radiation in UVC light destroys the cellular structure of bacteria and virus particles. This is sometimes described as a “photolytic” effect.
UVC light is often used in conjunction with other cleaning and sterilization techniques, such applying dry or moist heat, using filters or spraying chemical agents to sterilize or destroy microorganisms.
Unlike chemical agents, UVC light doesn’t produce any potentially harmful byproducts.
Should I use a UVC lamp in my home?
No. The products sold on this website are meant for commercial use only. They require training to be used safely and effectively.
UVC light can damage skin, eyes and tissue if used improperly.
What are some of the commercial applications of UVC light?
In the late 1800’s, two British scientists discovered that UVC light could kill microorganisms, germs, bacteria, viruses and mould.
Westinghouse developed the first UVC germicidal lamp for use in hospitals in the 1930’s.
Today, UVC lamps are used to sterilize air, water and surfaces in a variety of settings:
- In health care, UVC lamps are used in conjunction with other cleaning agents to purify air and surfaces in high-traffic zones and patient rooms. Surgical equipment is usually sterilized using UVC lamps.
- Food manufacturers, retailers and warehouses use UVC light to reduce mould, thus extending the shelf-life of fresh products.
- Many municipalities remove chemical-resistant parasites in their water purification processes using UVC lamps.
- Airlines use UVC lamps to efficiently clean surfaces, seats and air between flights.
- Hotels use UVC lamps and other cleaning agents to sterilize rooms between uses.
What length of time is sufficient for UVC light to sterilize air or surfaces?
The answer depends on the type of lamp you’re using and what you’re using it for. You should select equipment for optimal, functional UV to complete the task and minimal risk to the people using it.
Standard guidance suggests that users should select only the wavelength, irradiance and beam spread necessary to complete the task required. UV light exposure limits must be observed in order to avoid adverse health effects.
Many organizations adopt a practice of attempting to remove surface contaminants with a traditional cleaning process before using UVC equipment.
What are the risks of using UVC light?
UVC light can damage skin and eyes. The effects could be short-term (e.g. immediately after one incidence of overexposure) or chronic (cumulative as a result of long-term use). Damage, such as burns or inflammation, could be very painful.
Employers must ensure that their workers and contractors are properly trained, informed and equipped to use UVC light.
If UVC is used to sterilize air, surfaces or water, it needs to be done using a system that prevents both UVC leakage and any unintended exposure from exceeding normal levels.
Manufacturers will list the following information on devices and in instructions:
- Hazardous use warnings
- Pre-operation checklist
- Control measures for safe work
- Maximum Permissible Exposure Times (MPEs)
- UV light Exposure Limit Values (ELVs)
- Personal Protective Equipment (PPE) to wear while using the device
- Environmental requirements during use
- Proper maintenance and storage
When using any work equipment, the emphasis should be on prevention of injury, protection of workers and effective application.
What type of UVC lamps are right for my organization?
Your choice of UVC lamp will depend on the environment, application and intended use.
Low-pressure lamps are the most efficient way to generate safe levels of UVC. The radiation generated is almost exclusively at 254nm, which is 85% of the maximum germicidal effect available.
The UV light emitted by a source is expressed in watts (W) and the irradiation density is expressed in watts per square metre (W/m2). To eliminate germs, microorganisms, bacteria, mould and viruses, pay attention to the dose of UV light required. The dose is the irradiation density multiplied by the time (t) in seconds and expressed in joules per square meter (j/m2). (I joule is IW.second).
The effective resistance of microorganisms to UV light depends on a variety of factors, such as:
- The organisms themselves
- Environment and surroundings
- The type(s) of surface(s) you are trying to sterilize
- Air temperature
Air can be purified using UVC light because it doesn’t absorb much (if any) light and because most rooms in which UVC light is used are enclosed, which implies that airflow can be controlled.
Using UVC light to purify air could reduce the risk of airborne infections, such as COVID-19. That said, purified air in and of itself is not a purifying agent.
[We could include a similar chart to Table 2 in the Philips handout that Nathan sent to me.]
Are your products guaranteed?
Warranties are issued by manufacturers listed on our website, and are specific to each product. Most offer a limited one-year warranty from the day you receive your product(s).
How long do the lamps last?
The answer to this question depends on the volume and length of use, as well as the unique environment where the lamps are used. An output measurement device, such as a radiometer, would indicate the strength of UVC light emitted from your lamp(s). You will need to determine the range of output and the time available for workers to achieve the desired outcome, and calculate an acceptable bulb replacement cost.