A Reader writes:
There are a host of vendors pushing whole home UV purification of everything from sick house syndrome, legionaire's disease, to even biological terrorism not just for controlling mold growth on your AC coils (which was their original claim to fame).
Although some research seems to support their claims I suspect a lot of the talk is just hype.
I also suspect that many of the lamps are woefully undersized to do much good considering the volume or air and resulting air velocity in a modern HVAC (for a 3500 sq ft home typically furnaces push upwards of 2000 cfm).
Then there are all the new 'PCO' claims being made.
Vendors are claiming by simply adding a small sleeve over the UV bulb containing titanium oxide that VOC's and odors will be a thing of the past.... and you just can't consider purchasing a UV light for your HVAC without getting one with their proprietary approach to PCO.
One such vendor which heavily advertises these claims on the internet is Calutech Blueray.
Calutech has posted a ton of 'research data' which they suggest supports their claims.
I would greatly appreciate if you could shed some light on the pro's and con's of UV and whether PCO is ready for prime time yet or if it is really still just an 'experimental' approach still needing refinement.
Similarly your insights into which UV vendors (if any) are reputable would be most helpful.
I'm not that excited about ultraviolet "light" (UV) in air purifiers in general.
Currently UV is a marketing fad with everyone jumping on the massive "swine flu" big pharma/vaccine promotion/scam bandwagon.
In my opinion, the government-led bio-terrorism scare was absurd.
Duct tape and UV will not save us from any real bio-weapon - it will be everywhere, likely infecting most before an "epidemic" diagnosis by CDC can even be announced.
It will spread through hospitals and schools like wildfire, spreading by close human contact or unseen insect/animal vectors.
If you thought the government/FEMA was worthless on hurricane Katrina and the gulf oil disaster, just wait.
I don't blame manufacturers and vendors of whole-house ultraviolet systems for seeing the low cost marketing possibilities, but claims of flu interdiction are flimsy at best.
Claims that HVAC UV can do anything for dust mites are beyond hype.
I do agree that tuberculosis, which is coming back and requires relatively long-term airborne contact, can be reduced by HVAC and room UV systems.
Despite the fact that flu is spread primarily by touch and direct cough - transmission methods which air cleaners CANNOT block - consumers are rushing to buy uv added appliances.
Room air purifiers began appearing with ultraviolet lamps a couple years back, and the vast majority, especially in the lower third of the market, are worse than useless.
Now window unit air conditioners and humidifiers, notorious mold collectors, have UV.
Ice machines and refrigerators are also sprouting UV lamp appendages.
This is a way to mark-up cheap goods and add back end profits from overpriced annual lamp replacements.
That said, UV is the best HVAC/furnace plenum/air duct add-on, and the only one I recommend.
Central HEPA-filtered systems are not cost effective or efficient.
But a good UV system, combined with aggressive duct/coil/pan maintenance, can help keep microorganisms down.
Many people with "mold" issues will search the house in vain for leaks and condensation when the mold is blowing from their AC. (This is especially problematic in automobile AC systems.)
In AC-caused "moldy home" situations, central induct UV and better HVAC maintenance can sometimes save the day.
Photocatalytic (PCO) air cleaning has moved beyond the experimental stage.
PCO concept needs further development, most importantly in the UV emitter durability area.
But I see no safety reason not to add PCO to an induct UV setup.
Any UV lamp can be turned into a PCO by wrapping it in a blanket of Titanium dioxide coated material, like the Calutech "oxycat sleeve."
So far I have not heard of any harm directly attributed to a PCO installation.
I think PCO will add substantially to UV's anti-bacterial effects.
But partial oxidation byproducts are a possibility, especially if your space has airborne aldehydes/VOC (leather furniture, particleboard subfloor...).
Since the PCO materials - aluminum sheet and/or thin titanium dioxide catalyst layer - are cheap, it makes sense to add a PCO grid to any HVAC air handler UV "light" worth its salt.
But so many of the low-watt UV devices mentioned above are not worth much.
Mounting the emitter inside the metal duct removes one of my chief objections to typical germicidal UV systems - eye damage from escaping UV-C radiation.
Comparing brands and vendors of HVAC induct related products is really beyond my expertise.
These products have lower sales volume than leading room models, resulting in lower information density.
I suspect that this segment has shrunk even more than the room air cleaner market. Calutech might be the last man standing.
You are correct in stating that HVAC UV light systems must be powerful, and/or airflow needs to be slow, to give enough dwell time to damage microorganisms' DNA.
("germicidal" UV "light" does not kill outright, it causes mutations which degrade populations over time).
The UV Blueray manufactured by CaluTech, in a Chicago suburb (not China), is a powerful, dual 60Watt, whole house in-duct UV purifier.
Current Blueray power is advertised as creating a respectable 36,000 Microwatts (per second/cm square) exposure level, using 120 watts AC household current.
By comparison, competitor Second Wind offers 24,000 microwatts.
Other brands and lower powered inducts, including Calutech's Mini-Blue (18,000 MW) and Sanuvox R4000GX (16,500 MW w/reflective plenum) are less interesting.
Lesser brands generally avoid publishing their actual power output.
It looks like a rough estimate of UV output can be derived from the household current draw.
Many lesser room air purifiers have just 6-10 Watts, weaker inducts pull under 50W.
Calutech has been around for years, offers fair prices on replacement bulbs, and has a 10 year warranty on the unit.
When you add a device like this to your real estate, you are counting on the manufacturer to be solvent and stay in business for many years.
I cannot guarantee this in today's global financial climate.
Keeping the HVAC fan on 24/7 is required, this is neither cheap nor silent.
Frequent bulb changes are required for effectiveness - at least annually, even when the light still appears to be working.
The holes cut in HVAC metal are going to be there for the life of the system. Installation with a 2" hole saw through sheet metal is not my favorite way of doing things, but it is far easier than cutting a 4-inch hole with sheet metal shears.
The ideal ultraviolet induct installation is close to coils/evaporators on the supply (return) side of the HVAC system, be sure there is room on your HVAC system, and depth inside for the lamps, before purchase.
I'd say this project comes down to your budget and confidence in your mechanical skills. Professional installation adds $150-300 to the tab.
But HVAC germicidal UV is not a substitute for room air purifiers close to where your family breathes.
Claims that you can neglect HVAC coil/pan cleaning after installing germicidal UV are questionable.
This would be an interesting and useful home improvement project, though moneys invested will probably not be gained at resale.
Hey, at least the tax assessor can't see it.
You can see the