RE: Use of UVC Light In Air Handlers

[Guest guest]

Human invent products to fit a need. On the other hand, we also create market for a new profit-generating product. It is called marketing. Since when do we need to sterilize indoor air in regular residential and commerical buildings? Who needs to live in a sterile bubble? Since when do we need UV light to get rid of airborne viable microorganisms? HEPA filtration has been used in industrial clean room and research facility for biological hazardous material for many many years. Has it fail its purpose? Nope. Why do we suddenly need UV light now? Can we keep air handler dry and clean wothout UV light? It's been done before someone decide to put UV light in there. What changed? It's all marketing. Wei Tang QLab AirwaysEnv@... wrote: If spores or bacteria are flying by a UV light in a duct system you could have (and should have) filtered them with a good filter. If you made sure they didn't become airborne by preventing growth in the first place and by removing contaminants (not just viable spores) from surfaces if growth has occurred you wouldn't even need an especially good filter.I see no reason to install a UV light in a duct

system in a normal building -- maybe in an AIDS ward or where organ transplant patients recover or an animal laboratory where control of infectious biological agents is more critical.There are better ways to prevent growth on coils and in drain pans than relying on UV light.What would you need to kill in a duct system in a residence or office building? And wouldn't transmission of an infectious agent occur directly from fomites or aerosol droplets or suspended spores in the occupied space rather than from a supply diffuser or register?People seem to feel that high-tech, expensive gizmos, especially ones that are shiny with bright lights, are needed to kill things they can't see. It's money poorly spent, in my opinion. Why it was a requirement at one time for GSA buildings and why the USGBC considers it worthy of LEED credit is beyond me.Steve TemesIn a message dated 1/17/2008 10:31:20 AM Eastern Standard Time,

wtangQLABusa writes: Besides time, the dose of UV exposure also depends on the distance of microorganisms to the UV source. The bacteria fly by 10 cm away from the UV is being killed roughly 100 times less effective than those fly by 1 cm away assuming the time of exposure is the same. Wei TangQLabCarl Grimes <grimeshabitats> wrote: ,That is my recollection also, even though many bacteria needed only a second or less exposure. Fungi, on the other hand, needed at least 5 seconds for the small translucent spores and as much as 3 minutes for the larger dark spores.Carl GrimesHealthy Habitats

LLC Wei Tang, Ph.D. Lab Director QLab5 DriveCherry Hill, NJ 08003 Faxwww.QLabUSA.com

[Guest guest]

Let me preface what I am going to post on the basis that I am on the fence regarding UV in HAVC systems; for several reasons. This said, I can speak of several projects that I was involved with, and where I saw the beneficial effects of UV – I was not involved with the UV system. In at least two of these projects, the effect of the UV was impressive......very impressive.

I have the literature somewhere regarding one manufacturer’s product who installs long skinny high output UV lamps with the lamps luminance focused on the impact side of the heat exchanger, i.e., just up-steam. These lamps have a shield on them so nothing impacts the lamp, and the shield reflects the lamps energy onto the heat exchanger. Within a 6 weeks of the lamps being used, the heat exchanger looked clean. 18 months later, the heat exchanger looked new, i.e., the metal was shinny clean without a spec of dust, dirt, detritus. If anything, these lamps were keeping the heat exchanger very clean. Installation costs were high, but operating cost were pennies per day. Cheap. Also, due to the lamps energy, the HCVAC system had to have LOTO controls, so the guys doing maintenance would not be harmed. These systems were installed in several schools and one community college.

The other UV source I saw being used was a plasma arch inside a quartz tube placed inside the ductwork of a hospital system. I believe that it was a Kaiser Permanente facility. The purpose of the arc was to allow more re-circulation, instead of 100% outdoor air, and kill everything in the re-circulated air. The plasma arc REALLY put out he UV! Made a welding rod look like a dim bulb, and that’s no understatement. All I could say when I saw it was Holey Crap! I also recall seeing lots of data on the quality of the air, and surface samples collected from the ductwork downstream of where the plasma arc was installed......an nothing appeared viable. It was almost as if the arc was sterilizing the air – approx 8,000-SCFM in a large duct that I can’t recall the size; maybe 36x48. Don’t know. BTW, this system was installed in an HVAC system serving an infection ward, and I was told by a hospital architect that the cost of operating the arc in the summer time was a wash with the energy saved by not using 100% outdoor air, but savings were to be realized in the winter. Moreover, by operating the arc, they felt that they provided a much safer environment for staff, i.e., it was an engineering control in lieu of total and constant PPE.

For what it is worth....

If spores or bacteria are flying by a UV light in a duct system you could have (and should have) filtered them with a good filter. If you made sure they didn't become airborne by preventing growth in the first place and by removing contaminants (not just viable spores) from surfaces if growth has occurred you wouldn't even need an especially good filter.

I see no reason to install a UV light in a duct system in a normal building -- maybe in an AIDS ward or where organ transplant patients recover or an animal laboratory where control of infectious biological agents is more critical.

There are better ways to prevent growth on coils and in drain pans than relying on UV light.

What would you need to kill in a duct system in a residence or office building? And wouldn't transmission of an infectious agent occur directly from fomites or aerosol droplets or suspended spores in the occupied space rather than from a supply diffuser or register?

People seem to feel that high-tech, expensive gizmos, especially ones that are shiny with bright lights, are needed to kill things they can't see. It's money poorly spent, in my opinion. Why it was a requirement at one time for GSA buildings and why the USGBC considers it worthy of LEED credit is beyond me.

Steve Temes

Besides time, the dose of UV exposure also depends on the distance of microorganisms to the UV source. The bacteria fly by 10 cm away from the UV is being killed roughly 100 times less effective than those fly by 1 cm away assuming the time of exposure is the same.

Wei Tang

QLab

Carl Grimes wrote:

,

That is my recollection also, even though many bacteria needed

only a second or less exposure. Fungi, on the other hand, needed

at least 5 seconds for the small translucent spores and as much as

3 minutes for the larger dark spores.

Carl Grimes

Healthy Habitats LLC

[Guest guest]

Group, The reason I started this post was to question whether the LEED people

have sufficient knowledge to deal with IAQ issues. Here they are giving LEED

points for the installation of an UVC lamp. I doubt it is they type

described.

Something to think about.

Bob

________________________________

From: iequality on behalf of Geyer

Sent: Thu 1/17/2008 8:06 PM

To: iequality

Subject: Re: Use of UVC Light In Air Handlers

Let me preface what I am going to post on the basis that I am on the fence

regarding UV in HAVC systems; for several reasons. This said, I can speak of

several projects that I was involved with, and where I saw the beneficial

effects of UV - I was not involved with the UV system. In at least two of these

projects, the effect of the UV was impressive......very impressive.

I have the literature somewhere regarding one manufacturer's product who

installs long skinny high output UV lamps with the lamps luminance focused on

the impact side of the heat exchanger, i.e., just up-steam. These lamps have a

shield on them so nothing impacts the lamp, and the shield reflects the lamps

energy onto the heat exchanger. Within a 6 weeks of the lamps being used, the

heat exchanger looked clean. 18 months later, the heat exchanger looked new,

i.e., the metal was shinny clean without a spec of dust, dirt, detritus. If

anything, these lamps were keeping the heat exchanger very clean. Installation

costs were high, but operating cost were pennies per day. Cheap. Also, due to

the lamps energy, the HCVAC system had to have LOTO controls, so the guys doing

maintenance would not be harmed. These systems were installed in several

schools and one community college.

The other UV source I saw being used was a plasma arch inside a quartz tube

placed inside the ductwork of a hospital system. I believe that it was a Kaiser

Permanente facility. The purpose of the arc was to allow more re-circulation,

instead of 100% outdoor air, and kill everything in the re-circulated air. The

plasma arc REALLY put out he UV! Made a welding rod look like a dim bulb, and

that's no understatement. All I could say when I saw it was Holey Crap! I also

recall seeing lots of data on the quality of the air, and surface samples

collected from the ductwork downstream of where the plasma arc was

installed......an nothing appeared viable. It was almost as if the arc was

sterilizing the air - approx 8,000-SCFM in a large duct that I can't recall the

size; maybe 36x48. Don't know. BTW, this system was installed in an HVAC

system serving an infection ward, and I was told by a hospital arch! itect that

the cost of operating the arc in the summer time was a wash with the energy

saved by not using 100% outdoor air, but savings were to be realized in the

winter. Moreover, by operating the arc, they felt that they provided a much

safer environment for staff, i.e., it was an engineering control in lieu of

total and constant PPE.

For what it is worth....

If spores or bacteria are flying by a UV light in a duct system you could have

(and should have) filtered them with a good filter. If you made sure they

didn't become airborne by preventing growth in the first place and by removing

contaminants (not just viable spores) from surfaces if growth has occurred you

wouldn't even need an especially good filter.

I see no reason to install a UV light in a duct system in a normal building --

maybe in an AIDS ward or where organ transplant patients recover or an animal

laboratory where control of infectious biological agents is more critical.

There are better ways to prevent growth on coils and in drain pans than relying

on UV light.

What would you need to kill in a duct system in a residence or office building?

And wouldn't transmission of an infectious agent occur directly from fomites or

aerosol droplets or suspended spores in the occupied space rather than from a

supply diffuser or register?

People seem to feel that high-tech, expensive gizmos, especially ones that are

shiny with bright lights, are needed to kill things they can't see. It's money

poorly spent, in my opinion. Why it was a requirement at one time for GSA

buildings and why the USGBC considers it worthy of LEED credit is beyond me.

Steve Temes

In a message dated 1/17/2008 10:31:20 AM Eastern Standard Time,

wtang@... writes:

Besides time, the dose of UV exposure also depends on the distance of

microorganisms to the UV source. The bacteria fly by 10 cm away from the UV is

being killed roughly 100 times less effective than those fly by 1 cm away

assuming the time of exposure is the same.

Wei Tang

QLab

Carl Grimes wrote:

,

That is my recollection also, even though many bacteria needed

only a second or less exposure. Fungi, on the other hand, needed

at least 5 seconds for the small translucent spores and as much as

3 minutes for the larger dark spores.

Carl Grimes

Healthy Habitats LLC

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