Thread Tools Display Modes
Old 07-16-2012, 08:34 AM
carlb carlb is offline
Join Date: Dec 2004
Location: Palmetto Bay, FL
Posts: 1,112
UV light as germicide in A/C unit

Looks like it's time to replace the a/c system in our house. I'm in the quote-gathering process, and I've been getting the option to install a UV light in the air handler as a germicide. Anything definitive on the effectiveness of these things? My Googling has turned up a lot of literature from HVAC companies, but precious little from anything that looks like an impartial source.

FWIW the house is in Florida, which seems to grow creatures of various sizes at an alarming rate, so anything that legitimately cuts down on the number of organisms residing in my house at any one time is worth considering, IMHO. I just want to make sure I'm not buying into any woo.
Old 07-16-2012, 08:57 AM
lazybratsche lazybratsche is offline
Join Date: Feb 2006
Posts: 3,713
It's definitely not woo, UV is used to disinfect lots of things. Some sewage treatment plants will use UV as a back-up method of disinfection, to kill the occasional bug that survived earlier treatment steps. In biology labs, UV lights are used to disinfect sterile cabinets, though again it's a back up meant to catch anything that's survived other cleaning methods. I've used UV light to kill a thick layer of E. coli on a petri dish. 10 minutes exposure under really really bright UV lamps will kill most (but not quite all) bacteria.

Now, in an AC system I can't say how effective it'll be. At the very least, it should slow the growth of whatever is inhabiting the system. So if you have some aggressive molds that like to grow on, say, the evaporator coils or filters, that UV light should mean that you don't have to clean or replace things quite as often. I can't say if it'll make a practical difference though.

Last edited by lazybratsche; 07-16-2012 at 08:59 AM.
Old 07-16-2012, 09:02 AM
Red Stilettos Red Stilettos is offline
Join Date: Jun 2004
Location: ATL, GA
Posts: 1,050
One thing to keep in mind is that the UV bulb will need to be changed fairly frequently to maintain efficacy, especially since it will be on constantly. I used to manage a aquatic system that used UV sterilizers to cut down on bacteria and algae. We changed the bulbs every 6 months, and I could tell when it was late, as the water started turning green. And the bulbs aren't cheap.
Old 07-16-2012, 09:13 AM
carlb carlb is offline
Join Date: Dec 2004
Location: Palmetto Bay, FL
Posts: 1,112
Thanks, all. I knew UV had germicidal effects, but didn't have any direct experience, or any knowledge as it relates to a/c systems. I think I might go with it; like I said, anything to keep all the wee beasties at bay.
Old 07-16-2012, 11:21 AM
Smeghead Smeghead is offline
Join Date: Apr 2000
Posts: 18,793
Before you commit to anything, I'd find out exactly how powerful the bulb is, and exactly how far away it is from the surfaces it purports to be disinfecting. You need quite a strong UV intensity to really do anything. We had UV disinfection bulbs in some of our lab hoods, and when we once measured the intensity of UV light actually reaching the hood work surface, it turned out it was no more effective than waving a blue light in the general direction.
Old 07-16-2012, 11:40 AM
beowulff beowulff is online now
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 15,275
I'd vote for "Big waste of money."
Old 07-16-2012, 11:52 AM
Really Not All That Bright Really Not All That Bright is offline
Join Date: May 2003
Location: Florida
Posts: 67,429
UV light applied to the coil will keep colonies from growing on the coil. UV light shone into the airstream will do absolutely nothing. We were offered systems which included both types of UV light installation when we had our handler replaced last year (and wound up plumping for neither, for what it's worth).
Old 07-16-2012, 04:35 PM
NBYodo NBYodo is offline
Join Date: Nov 2005
Location: +61
Posts: 165
We had a rep from Steril-aire ( in at work for commercial HVAC, but they appear to also do residential systems.

We weren't specifically looking for air quality improvement systems, but they also claim energy usage improvements simply from increased airflow due to reduction in pressure drop across the coil from the biofilm.

They indicate replacing the bulbs every year is the only typical maintenance required.

Case studies on their website.

YMMV. INASterilAireFlogger.


Last edited by NBYodo; 07-16-2012 at 04:35 PM.


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump

All times are GMT -5. The time now is 06:41 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.

Send questions for Cecil Adams to:

Send comments about this website to:

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to:

Copyright 2018 STM Reader, LLC.

Copyright © 2017