Replies

1. 
   Bill Friend CHI, CMI | Jul 17, 2010 02:38pm | #1

   UV light in the right wavelength can cleanse the air but it needs time in which to do it. Do some research to find out how long bacteria, mold spores, etc. must be exposed to direct UV light and what wave lengths work best. I believe you will find placing one or two of these lights inside your duct work will have little benefit due to the speed at which air is pulled past them. The most effective placement would be shining directly onto the cooling/heating coils.

2. 
   Daniel Ernst | Jul 17, 2010 04:03pm | #2

   Hi Gary,

   I supervised in an aseptic processing facility for several years (Class 100 cleanroom used to produce injectable antibiotics). There we used UVGI to sanitize certain surfaces.

   I would question the efficacy of any system claiming germicidal treatment of moving air. Although UV is commonly used for sanitizing water (and less frequently surface contamination), air is a much more difficult proposition.

   To clean air, you use filters. To sanitize the air, you use HEPA filters, which have a very specific definition, and very specific set of parameters for particle size and efficiency.

   Any technology used to killing bacteria or viruses depends on dose (strength), penetration, and dwell time. With the Ultravation system you fall short on all three parameters:

   1) Dose- It's relatively small (flourescent lamp inside a pleated metal box).

   2) Penetration - Bacteria can be shielded from UV by particles the size of a single skin cell. Since bacteria typically hitch a ride on larger particles, the penetration is poor for UV light systems. Also, vegetative cells are relatively easy to kill. Endospores (dormant cells) are not. Many bacteria and molds produce endospores. They are tough; they resist penetration.

   3) Dwell Time - If the air was held captive in a small chamber for 15 minutes, then the bacteria and viruses might be exposed long enough for the UV to break down the cell walls. Air moving through an AHU > 1,000 CFM does not have enough dwell time - perhaps a fraction of a second.

   There are a host of other problems with these systems. Dust builds up on the bulb, limiting their output. The bulbs degrade, the UV output gets lower and lower (how would you like to replace that expensive bulb every 6 months?).

   I'm quite sure that UltraVation company couldn't provide you an independent test to show the efficacy of their system (from an industry perspective - sanitization requires a 3-log reduction, sterilization requires a 6-log reduction).

   Further reading:

   http://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradiation#Air_sterilization

   Finally, you need to question the purpose of such a system. The air you breathe is filled with thousands of particles. Bacteria are everywhere. Most of the time they are harmless OR beneficial.

   That's a long winded answer, but hopefully it's helpful.

   I understand the desire to clean your household air, but any filter with a MERV rating of 8 - 12 should more than do the trick. Don't fall for this complicated and expensive UV system . . .

3. 
   MICHAEL CHANDLER | Jul 18, 2010 02:27pm | #3

   Some people with sensitivity issues do benefit from these UV systems to the point that they can tell when the bulb burns out due to the health effect and those effects are improved by replacing the bulb.

   However I would recommend really good duct sealing with before and after duct blaster testing by a third party and a MERV 11 or 12 filter as the first step.

   I also like to install multiple MERV 11 filters in filter grills rather than at the air handler cabinet to make it easier to inspect and replace and to increase the surface area of the filters (by having two or three rather than one).

4. 
   wjrobinson | Jul 20, 2010 01:23pm | #4

   Future parents... get your kids dirty.

   Living inside sterile space is not living.

   So many trends today need to go in the opposite direction.