UVC Knowledge

Home>Resources>UVC Knowledge

How to choose a high-quality UV LED lamp?

Time: 2020-07-16

While the global economy may be crippled right now, one technology that brought a close of hope to many industries this past quarter was the UV LED system.

 

If you ever spy the opportunity, then you may already hear a popular related product, that is, the air-conditioning UV LED system made in the USA.


UV lamp

 

Judging from the advertisement description, this product is awesome:

 

1. UV LED spectrum is safe for eyes & plastics

2. Replaceable and trimmable adhesive UV LED strip

3. 50,000+ hour expected UV LED life

 

But if you have enough UV LED knowledge, you will easily find that these descriptions are completely contradictory.

 

Starting with this product, we will tell you how to purchase UV LED products correctly.


What is the wavelength of UV LED


Like the air-conditioning disinfection system made in the USA, many UV products are advertised to achieve sterilization effect through UVC LED, which may not be the truth.

 

First of all, we need to note that not all ultraviolet rays have a bactericidal effect. There are nuances among UVs, too. UVA, UVB, and UVC represent UV radiations of different wavelengths.


different uv light

 

UVA, 320-400nm. It has strong penetrating power and was widely used for curing, printing, currency detecting, etc. UVA Lightdoes not have the ability to kill bacteria.

 

But it is the best wavelength band for exciting photocatalyst for sterilization. The excitation efficiency of UVA is about 5 times that of the same radiation UVC. Not to mention that with the same cost, the radiation of UVA is almost 1000 times that of UVC LED.

 

UVB, 280-320nm. It has no sterilization effect and was widely used for health care and treatment of skin diseases.

 

UVC, 100-280nm, is popular for its sterilization effect. It works by destroying the DNA or RNA of the bacteria&viruses, making them inactive and unable to reproduce.


Related Knowledge-


Benefits and risks of different ultraviolet light 

 

Since the lifespan of single bacteria&viruses is very short, once they lose the reproduce ability, it means death. So the purpose of sterilization has been achieved.

 

Secondly, whether it is UVA, UVB, or UVC, direct exposure certainly will cause harm to human health.

 

According to the carcinogens list provided by the World Health Organization, 100-400nm ultraviolet radiation belongs to Class I carcinogens.

 

Even 222nm UVC LED is still in the laboratory testing stage and its safety cannot be completely determined.


Related Knowledge-


Is Far-UVC light (222nm) efficient and safe?

 

Now we will go into the identification phase.

 

As an ordinary consumer, it is almost impossible for you to have a device at home that measures wavelength in realtime (aka a spectrometer), so mastering the basic UV LED knowledge is necessary.

 

For example, UVC is invisible light, and people can hardly see it. If you find that the UV LED is pretty bright, don't doubt, it cannot be UVC, but UVA, or even ordinary LEDs that emit purple light.

 

In addition to the advertisement that ultraviolet rays are harmless to the human body and plastic, it is obvious whether it is a UVC LED or not.


What is the carrier of UV LED?


You might consider the UV flexible light strip is an ideal carrier since it can be replaced and trimmed according to your needs. However, professionals have different opinions.


LED UV light bar

 

(1) Heat dissipation of UV LED

 

Compared with light bars, flexible light strip are always inferior in terms of heat dissipation. This is why the wattage of its light source is so low.

 

Further, considering that the LED chip is sensitive to heat and the lifespan will be halved every time the temperature rises by 10 degrees, so the lifespan of the light strip will not be too long.

 

(2) Moisture-proof degree of UV LED

 

There are generally three types of flexible light strips: IP20 non-moisture-proof bare board, IP65 waterproof glue board, and IP67 waterproof casing board.

 

Due to the high humidity inside the air conditioner, IP20 bare board is not considered at all.

 

As for the IP65 glue board, in addition to the terrible heat dissipaton ability, another problem is that UVC cant penetrate the layer of glue at all. Because the penetration ability of UVC is pretty low and everything can block it except for the quartz glass. Since UVC cannot penetrate the glue, sterilization is impossible.

 

Of course, almost few manufacturers will use IP67 waterproof casing board for the flexible light strips.

 

In general, this is not a suitable carrier.


What is the lifespan of UV LED?


Like the air-conditioning disinfection system made in the USA, many UV products are advertised to be more than 50,000h. However, it’s impossible at all. Only ordinary LEDs can achieve 50,000 hours at L70 (After using 50,000 hours, lumen will decay to 70% of the original data. )

 

But in the field of UVC LED, it's difficult to reach the technology level. Why?

 

1. The light decay of the UVC LED chip will be particularly fast in an environment with oxygen or moisture.

 

2. Oxygen from outside will easily enter the inside of LED through the glue.

 

3. UVC will continue to damage the glue and further increase the oxygen from outside. Then the light decay will continue to occur.

 

Therefore, for ordinary UVC LEDs without inorganic packaging and vacuuming process, the L50 lifespan is about 1,000 hours or even 300-500 hours.


How to assemble the UV system?


Although manufacturers take UVC LEDs as light sources, we cannot easily believe in their sterilization effects.

 

Why? Because in the flowing air environment, the sterilization effect of UVC LED alone is not enough.

 

Ultraviolet rays cannot take effect in an instant, instead, the sterilization process is continuous. Just like a submachine gun, ultraviolet rays will continuously release a lot of energy in one direction. After several consecutive impacts, bacteria or viruses can be killed thoroughly.

 

Pay attention to one thing, although UVC does have a Sterilization effect, its effect is a combination of ultraviolet energy and irradiation time. If UV dose is insufficient, the bacteria will only temporarily lose activity, and then slowly repair their own structure.

 

This also means, if bacteria and viruses are moving fast in the air, UVC is almost impossible to completely kill them.

 

Regarding the sterilization effect of UVC, my team did an experiment in a room with the volume of 40m3.


uv experiment

 

The radiation power of an ultraviolet mercury lamp installed in the air-conditioning duct is 18W, and the effective radiation distance is 0.2 meters.

 

According to the industry standard, the UV dose required for 99.99% inactivation rate is 40mJ / cm2.  

 

Then we provide an air conditioner with 550m3/h duct air volume and 200mm*200mm duct size. Guess how long it takes to disinfect the entire room?

 

The answer is 100.28 minutes, which is approximately 1.67 hours.

 

But this is a mercury lamp!

 

Although mercury lamps are dangerous, and civilian mercury lamps will be withdrawn from the Chinese market from year 2021, its cheap and high energy.

 

If we want to use UVC LEDs to achieve the same sterilization effect as mercury lamps, it may cost  several thousand dollars.

 

And this is the most fundamental reason why we use UVled+photocatalysts.

 

As long as one or two cycles (4.36 minutes or 8.72 minutes) can complete the elimination of the entire room, at most only using ultraviolet light alone. 10% of the lamp time.


Where to place the UV LED system?


Although manufacturers take UVC LEDs as light sources, we cannot easily believe in their sterilization effects.


As I mentioned before, whether it is UVA, UVB, or UVB, direct exposure will cause harm to the human body.

 

Therefore, we should pay special attention to the UV leakage problem.


uv leakage

 

Like the air-conditioning disinfection system made in the USA, the installation position of the light bar is at the air outlet.

 

If the light source used by this company is UVC LEDs, and we live under the air conditioner everyday, then how terrible it is to our skin and eyes!

 

All in all, a qualified UV sterilizer should meet at least five standards:


1. Real UV LED

2. Good heat dissipation and moisture resistance

3. Inorganic packaging LED

4. Effecitive and efficient sterilization

5. No UV light leakage

 

Related ArticleThe ultimate buyer's guide on your UV Lamps purchasing


Efficient UVC LED solution for Minisplits


Efficient UVC solution for HVAC Units