|Ultraviolet Light Used for Mold Prevention in Air Duct Work Mold growth control by uv light mounted in HVAC air conditioning and heating ducts by Jay Bennett|
|From Jay Bennett|
The Professor doesn't understand the real use of UV lamps in residential air conditioners. The UV lamps are mounted in the duct right next to the condensation pan. In hot humid climates, these pans are reservoirs for mold colonies. The purpose of the UV lamp is to prevent the growth of the mold, not kill the mold spores or bacteria passing through the duct. The lamp really isn't strong enough to sterilize all the air passing through the duct. A properly made UV lamp system is designed to produce as little ozone as possible. The ozone should completely recombined before the air is exhausted into the living area.
No I don't sell or profit by the sale of UV lamps. But I am thinking of getting one someday when they become a little cheaper to install.
From: DerekLafer@aol.com (mailto:DerekLafer@aol.com)
Editor's note. NQ environmental are the manufacturers are the Clarifier machine found on our site.
I would like to reply to Professor Thad Godish's assessment of the viability of UV systems in a residential air handling system. My name is Derek Laferriere, and I am the Vice President of Commercial & Medical Sales for NQ Environmental Inc.
While most of Professor Godish's statements were true, some of what he has said is misapplied or not completely stated, and his final judgement on the merits of UV are invalid. My company has been making HEPA/Ultraviolet Air Treatment Systems for high risk infection control applications (TB Isolation Rooms, Laboratories, Bronchoscopy Suites, etc..) for almost nine years. We were on the forefront of the use of UV for destroying airborne bacteria and viruses in the hospital market before the explosion of small ineffective UV systems in the commercial/residential market. In his reply, Professor Godish acknowledged the efficacy of UV for use in the hospital market. As such, it should follow that when the technology is used correctly, the same efficacy should hold true in the commercial/residential applications.
Professor Godish's assertion that there is little need for UV in HVAC systems due to the time it takes for the microorganisms to enter the system and get deactivated is valid to a point. Contaminants that are created and or dispersed "in-room" cannot effectively be removed by a central HVAC system. But this is due to the limitations of the air conditioning system, not that of UV, in that it is a difficult and very slow process for air conditioning systems to completely remove smoke, dust, odors, etc. from a room.
This is why we recommend either portable or wall-mounted units for individual rooms. In-room units that create effective air flow patterns can move or remove contaminated air, thereby preventing the spread of infectious air within a room. Our commercial/residential units (used in thousands of homes and offices), like our hospital product line (used in hundreds of facilities across the world), sends clean air to the ceiling where it can spread across the room, pushing contaminated air to the floor, out of the breathing zone, where it can be drawn back into the unit. This type of laminar-flow air flow pattern is recommended by the Center for Disease Control for infection control purposes. Central forced air systems are just incapable of creating such an air flow pattern, so I agree that the viability of a UV system in an HVAC system is limited for in-room contamination.
HOWEVER, UV in central HVAC systems can be used effectively if it is used to prevent contamination within central systems. Mold, bacteria, and virus growth inside ductwork are the primary contributors to Sick Building Syndrome. The moisture and warmth found in around air conditioning coils and within ductwork create an excellent host environment for any number of bacteria and disease, most notably Legionella. If installed next to drip pans and along A/C coils, simple UV lamps can destroy and prevent mold and other microrganism growth. It is these mold spores and bacteria that cause many people's allergic reactions and sicknesses, and which cause foul odors to come from your air supply. Therefore, small UV lamp systems can provide a valuable service inside air conditioning systems, but their goal would be limited to controlling the spread of microorganisms from the ductwork.
As such, I must wholeheartedly disagree with Professor Godish's assessment that UV lights in most air cleaning systems is a "snake oil kind of thing". They can provide a valuable service when their capabilities are understood. A major problem we have as a UV manufacturer is the misinformation prominent in the marketplace about UV. People with no UV experience have "developed" UV units that they say can peform a multitude of tasks, and this is what they preach to the consumers. I have seen hundreds of such units where the companies maintain their single UV lamps will remove bacteria, viruses, dust, odors, chemicals, particulate, ions, etc. from any air stream. These are just unrealistic expectations from people with little understanding of how UV works.
The fact remains that UV is capable of only doing so much. Airborne bacteria and viruses can be destroyed, but this requires that the unit be engineered and designed to create a high UV dosage. UV dosage is a factor of the intensity of the UV light, and the amount of time the microorganism is in contact with it. Suffice to say that a single lamp in a residential AC system will do little or nothing to destroy airborne bacteria as many manufacturers will insist, given the one (or two) lamp(s) have little intensity and the air passing by it goes upwards of 1,500 cubic feet per minute. Any interested consumer should ask their salesman what the UV dosage is of the unit they are considering. If the salesman cannot come up with a UV dosage (which is different than the intensity of the UV light), then this person does not know what they are selling.
Finally, regarding ozone production, we at NQE acknowledge the unhealthy nature of ozone, so we use non-ozone emitting UV lamps. While ozone is a natural byproduct of UV lamps, lamps do exist that prevent the ozone from being emitted from the lamp. Lamps having special quartz keep ozone within the lamp, preventing ozone leakage. Ozone emission is therefore not inherent in all UV lamps, as Professor Godish indicated; it only occurs where this is a desired result.
Most commercial UV units use ozone emitting UV lamps for the added odor reduction achieved by the ozone. However, these units, in my opinion, are quite dangerous given that ozone can be harmful and potentially lethal in high enough quantities. Given these ozone emitting lamps cannot effectively control the ozone output (it varies with the amount of air passing by them), I agree wholeheartedly with Professor Godish's assessment of ozone. But I would like to confirm that non-ozone emitting UV lamps do exist (trace amounts can be emitted, but this is significantly less that that of a computer printer), and are used widely in our hospital and commercial/residential equipment.
In all, UV systems in residential and commercial air conditioning systems do provide a worthy service if applied correctly. Smaller systems can be effective in preventing mold and bacteria growth on A/C coils and the drip pan, or in other high moisture areas. And larger systems that are engineered to create a high UV dosage can be used to effectively disinfect supply air or return air (air returning from the house or building). They are also key aspects of infection control in commercial and medical facilities, to deter the spread of sickness from room to room or floor to floor (such as in a Nursing Home). Again, these units are more than simple one or two lamp systems, as they are typically a series of UV lamps, and they need to be custom designed on a case by case basis to ensure the proper UV dosage is created.
In short, the rapid rise in UV units on the market and they manner in which they are misapplied has certainly discredited our use of UV in these areas. However, with proper education, and most importantly the correct application and expectations of this technology, UV can be an invaluable tool in creating healthy air in your home and office.
Derek A. Laferriere
Vice President - Commercial & Medical Sales
NQ Environmental Inc.
Clarifier machines can be found at