There's a recently posted thread that asked about the effectiveness of ultraviolet light bulb germ killing properties and a forum member who has a lot of experience with such bulbs had some good info. to share. Unfortunately I can't remember the title of the thread or the member's name so I'm creating this thread hoping someone will link me to the other and/or answer these questions:

- Are there different frequencies of ultraviolet light where some are useful at germ killing while others are not - or is all ultraviolet the same?

- Do the germ killing properties of ultraviolet light bulbs stay at the same level until they burn out, or do they degrade to zero even though the bulb is still lit?

- If the bulbs degrade while lit, what is a good rule of thumb as to when to replace them?

And
Are there L.e.d .
U v. Lights?

I cannot answer about germs, however, there are UV L.E.D.s. I have a small UV L.E.D. flashlight that I use to find scorpions invading my house. It seems that they fluoresce under UV and shine like a beacon.

Possibly this thread?

https://sigforum.com/eve/forum...400075734#3400075734

No, that's not the thread but I appreciate the search. The one I'm thinking of is within the past month.

I was hoping someone - especially the forum member who posted their career experience regarding UV bulbs - would remember and direct me to the link and save me some time. That's alright, though.

Edit to add:

Found it!

https://sigforum.com/eve/forum...330060105#1330060105

I was using the search "ultraviolet" with no success. Didn't think to try "UV" until just now.

sadlerbw is the forum member I was trying to remember and need to contact to get answers to my questions.

Hey there! Let’s see if I can answer without getting too chatty.

1. No, all UV is not the same. Around 260-280nm is what you want for killing germs.

2. Bulbs don’t usually change the frequency of light they put out too much over their lifespan, but some of them will get weaker in terms of power output as they age. The Flourescent type in particular will get weaker just like regular old fluorescents do. If the ends of the tube are black, or the tube flickers a lot and doesn’t want to start, replace it. LEDs tend to have individual lights in a string or panel just die and shut off. The big mercury arc lamps tend to just die completely when they go as well, but I don’t think they use those in home AC stuff. I’d say if more than 20% of the individual LEDs in a panel/string are dead, that is probably enough that it is worth replacing.

3. The vast majority of germicidal UV lamps in the power range an AC system would use are going to be LEDs or Flourescent tubes. I’d stay away from anything that looks like an incandescent bulb. Don’t try to get some monster mercury arc lamp either because those run so dang hot it may warm up all your cold air before it gets out of the ducts!

If you have other questions, feel free to post them and I’ll answer if I can. I’m not an expert or anything. I just had to work on a project for a while that was all about killing germs with UV light and I picked some stuff up along the way from the actual
Scientists. I just worked on the software!

- Bret

Many thanks for the info., Bret. The knowledge you provided really helps in understanding, and differentiating, the useful from the useless.

These are the specific bulbs I've been using in my TRACS air filter -

https://tracspurifiers.com/pro...vc-replacement-lamps

From your explanation in the other thread and here, it seems like they are proper UV light bulbs, right? Color seems right as does the frequency range (254nm), but is the filament just an incandescent or is it a form of quartz?

Side note: The last set of bulbs I bought from TRACS were made in Hungary - which I was surprised, and pleased, to see as I had assumed they were going to be just another item from China.