CFL and UV lights usage

In the new era of LED (Light Emitting Diodes), most of consumers start forgetting CFL (Compact Fluorescent Lamp) & CCFL (Cold Cathode Fluorescent Lamp).
It is very strange phenomenon. It hasn't been even few years, when all supermarkets has been filled with CFL lamps. Majority work places had Fluorescent tubes with starters or ballasts. We all remember how we carefully taken off burned cylindrical fluorescent tubes from light fixture and exchange for new one.
Now all supermarkets filled with LED lights and only highly specialized stores has fluorescent bulbs.
And one might say: so what, one comes in to kick another out. Not that fast...apparently fluorescent tubes received second life.
Lets see why.
Fluorescent tubes or lamps are low-pressure gas discharge( plasma)- lamp. Most common is Low Pressure Mercury Lamps which has mercury vapor. Mercury needed to create low pressure plasma with much lesser energy and thus lamp wouldn't get hot and glow more efficiently. Gas inside that tube become plasma and mostly glow in UV (ultra violet light).  Fluorescent lamp has phosphor coating on the inside of the lamp and that coating flow visible light from UV bombardment. Typical luminous efficacy of fluorescent lighting systems is 50–100 Lmens per Watt. This is several times the efficacy of incandescent bulbs. But LED technology improved lately so much, that they bit CFL by almost doubling efficacy and has on average 180 lumens per watt. This is why at similar brightness, LED bulb would be close to a half power consumption. And when it comes only a few watts power consumption, LED light would be without a doubt a champion with brightness and efficiency.

This is room light spectrum from CFL light.
With covid hysteria lots of people became "sterility"conscious and wish to use different kinds of germ and virus killers. This is where Fluorescent bulbs found their second breath.
If we don't have phosphor coating, bulb would glow bright UV light and more so at 254nm and even 185nm wave lenght. Typical UV-LED diodes emitting at 385nm, 395nm or 405nm. Some very high end LED has 365nm, which I never say at reasonable price. So clearly, Low pressure lamps are the champions here with harder UV spectrum and efficiency glow.


For those who are not specialist in physics of light, 254nm is way more efficient at killing viruses and germs then even best and most expensive 385nm LED. We are talking about many times more efficient. In fact 385nm might not even kill viruses if applied less then 30 minutes and in 1 hour virus might die by itself in an open air without any light gizmo. Imagine you buy $100 worth fancy looking blue light led thingy and it is worth the same as just opening window for 5 minutes and get some fresh air.

On this picture germisidal lamp powered by DC ballast.
UV lamps with plasma glow (like low pressure mercury) are realistically way more productive at sterilization. Way to judge is by taking 10-15 minutes stand around lamp. If you get sun ten withing 3-4 sessions, the lamp will for sure do something about biological life forms (like viruses).
Myself, I actually burned my skin a few times with experiments on UV mercury lamps and power supplies for them. Please note: protective eye care is a must! You could and will damage your eyes with looking at UV mercury lamps. This is simply because pupil won't construct on UV light simply because human eye don't see it well, especially at small wavelengths. If 385nm you can see as "screaming, sharp" blue, 254nm you won't be able to see. The only reason why you see mercury light bulbs is because of glowing other materials from that wavelength.
In fact, UV lights very useful for gem hunting (yes, don't mix those with germ hunting). Most of gems starts fluoress under UV light and mercury lamps are way more efficient at doing that then LED lights. This is because of physics of energy excitation.
If made you exited about UV lamps, I invite you to my other article about how make or power UV light by yourself or if you wish, you could make them compact and battery powered. Also it is very common to use sterilization lamps in RV, cabins or boats. Please look in to this page for more information.

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