Air Quality FAQ

1. What is UVC?
   UV-C is a magnetic waveform like all waveforms emanating from the sun and like all them all, its frequency is unique as to its potential affects. It was found that this part of the UV family had germicidal results, especially at 260 nm. It was learned that the natural spectral line of mercury was 253.7 nm, very close to 260. When mercury was eventually vaporized in plasma, the germicidal lamp was born. Westinghouse light division was first to commercialize it in the early 1930's. It was then used extensively through the 1950's.

2. What is UVGI?
   UV Germicidal Irradiation, the same as UVC but the term more frequently used by the medical industry.
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3. What does it do?
   In the simplest of terms, it destroys the DNA of microorganisms causing cell death or making replication impossible.

4. Does it work?
   Yes, thousands of references to its efficacy can be found in the literature. The most recent of these can be found in our catalog. NIOSH and the University of Cincinnati cooperatively conducted the test. UVC is used worldwide, more in other countries per capita than in the US. Its largest use worldwide is the disinfection of water.

5. Will it stop allergies?
   Microorganism based allergies have shown abatement or complete remission with UVC. Even simple stuffy noses can be and have been cleared.

6. How do you size it?
   For mold, IAQ and maintenance, our Patent Pending application calls for one 24" fixture for every 4 square feet of coil surface area. The factory should always calculate any infectious disease applications.

7. Is it hard to install?
   No, installation drawings are available for every model and depending on the size of the unit and style of the fixture, installation time averages 15-20 minutes per fixture.

8. Where do I install it?
   Whenever possible, the light should be located downstream of and facing the coil. In this location the user can expect the highest efficacy in eliminating both surface and airborne Microorganisms.
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9. Does it replace filters?
   No, a UVC fixture is an air conditioning component that can be likened to several other of its parts. These include the coil, heating core, fan, dampers, humidification, filters, etc. All are designed to do some form of work within the air handler or on the air.

10. Don't filters remove microorganisms?
    Yes, one criterion in an infectious disease install is the efficiency and location of the filter. Excluding TB, the goal is to provide a reduction in overall numbers. With TB, the idea to approach elimination. Thus the filters can be taken into account when calculating the overall affect on the concentration of microbes. However, it should be noted that viruses can be as small as 0.02 micron in size, therefor, as you will encounter, the target organism needs to be known to calculate a properly functioning install. Most importantly, they do nothing to abate microbial growth on coils and in drain pans.

11. Is UVC harmful?
    No, UVC does not have the penetrating power that UV-A & UV-B do. It can make your skin red and your eyes feel grainy or burn, but, this usually recedes in 24 hours and does no lasting damage. If you ask, we have a relevant paper on this subject.

12. Does it produce ozone?
    No. Many UVC devices do produce ozone, but the Steril-Aire unit does not. A special compound blended into the quartz itself eliminates all frequencies produced below 200 nm, thus eliminating the possibility of ozone production.
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13. How does the residential unit differ?
    Steril-Aire started in the commercial/industrial market and by popular request, thought we should make a residential product. In order to get the job done and make it affordable, several things had to be decided. First, the entire coil needed to see light. Second, we to do it inexpensively. So we took the output of one commercial unit and spread it over two lamps, hence, the coil coverage. As such, the tubes and power supply cost much less. Next we made the box of galvanized sheet metal and that also helped.

14. Where do I install the commercial units and how?
    Steril-Aire fixtures were designed specifically for HVAC industry and with simple forms of installation in mind. To achieve the maximum benefit in a mold, maintenance and IAQ install, they should be located downstream of the coil. Simple installation instructions are included with each fixture and field install sheets are available for DE installations. CAD layout drawings for a specific install can be provided when we are informed of the dimensional specifics. For infectious disease applications , the factory must always be involved.
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15. What proof do you have it works?
    Lots and lots of successful Beta sites but the best clinical proof currently on record again is the Extended Abstract resulting from a joint effort between NIOSH and the University of Cincinnati wherein UVC was tested on the heartiest of Microorganisms known. This abstract is available from Steril-Aire.

16. Are your products UL approved?
    Yes. All Steril-Aire fixtures are both UL and CSA listed and labeled including outdoor use and damp locations.

17. How does your term UVC relate to UV or UVGI?
    The letters "UV" relates to the entire ultraviolet spectrum. This spectrum is broken down into four frequency ranges: Vacuum, Short Wave, Middle Wave and Long Wave or VUV, UVC, UVB & UVA. UVC is the frequency that is the most germicidal and the term UVGI refers to Ultraviolet Germicidal Irradiation as is used by Federal Agencies such as OSHA, NIOSH and the CDC when directly referring to UVC.

18. Do you clean a coil first?
    Maximum customer (and salesperson) impact results when you do not. However, it really comes down to time. UVC will degrade all of the organic material on and within a coil in a time frame unique to the application but usually ten days or less. But the depth of the coil, fins per inch and the level of contamination are the main time determining factors. Once you /or the customer se what the UVC will do, coil cleaning can be performed to hasten the process, but it is not a requirement.
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19. How will the customer know it is working?
    The best way to prove that there are potentially dangerous microorganisms and that you are killing them, is to use a petri dish called a contact plate containing malt extract agar for mold. Before the lights are installed, they are lightly touched to the coil surface and allowed to incubate for 48-96 hours. After the lights are installed, in the same place, the same procedure is followed. What will be seen is at least a 98% reduction in organism activity. The same can be done for the drain pan and a different medium can also be used for bacteria. Some of the other ways are:
    • Bioaerosol IAQ complaints (the majority of IAQ problems) will cease in as little as 24 hours.
    • A visible reduction of mold will be seen in less than three days.
    • For coils in service for 5 years or more, coil pressure drop will fall and drop as much as 30%.
    • Drain pans and drain pan water will become significantly cleaner in less than 5 days.
    • Direct line of site insulation will look like new in five weeks.
    • The air will seem fresher and most of all organic odors will disappear, even tobacco smells.

20. What is the warranty?
    The fixtures are warranted for 1 year and the tubes for 90 days.

21. What are the limits, temperature, humidity, velocity, etc.?
    One of the reasons for our existence was our ability to overcome the problems associated with conventional UVC products used in HVAC equipment. Essentially, Steril-Aire UVC Emitters have no limits in HVAC equipment, they were designed specifically for that use. Rules of thumb are 170 degrees Farhenheit, 99% RH and 1000 fpm respectively but contact the factory.
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22. How do you dispose of the used tubes?
    As you would dispose of any glass type trash. Following EPA guidelines specifically, Seril-Aire products either contains no hazardous materials or not enough to be considered as hazardous waste.

23. Should I cycle tubes on and off with the fan or run them continuously?
    When used for mold and IAQ control and when we look at what we are trying to accomplish, you can make the best case for running them continuously. Also, when we look at the tube performance, they run longer when ran continuously. So where possible, run them continuously.

24. How do you know when to change the Emitters?
    For infectious disease applications, change-out determination should only the result of using the radiometer and following factory specifications. For IAQ mold control, large installs can benefit from using a radiometer as well so that premature change-outs don't occur. It is common to change the lamps when the output decreases by 40%. For small installs or residential applications, relamping should be performed at least annually.

25. Do they need cleaning?
    Conventional UVC lamps must be cleaned every 90 days to maintain maximum output. Steril-Aire UVC Emitters produce so much output they degrade any impinged organic material. Therefore, they don't require periodic cleaning. Look at a used lamp!
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26. How do you clean them?
    When cleaning is necessary such as when the quartz has been touched, a Steril-Aire cleaning kit should be used or they can be cleaned with 99% or greater pure alcohol and a lint free cloth. Typically available alcohol contains too many impurities and too much water to work well. We provide a cleaning kit.

27. What if microbes are attached to dust particles?
    This is anticipated in our methodologies. For IAQ or mold control, we locate downstream of the cooling. There, the energy is focused and reflected thousands of millions of time per square inch throughout the coil increasing the flux density (number of photons) between the fins. Also, as this particle enters the coil, it is already tumbling or will tumble as it passes through allowing the reflected energy (360 degrees globally) to contact the microorganisms constantly. This is why an IAQ install can provide a rather high single pass kill ratio on most airborne microbes. It is also why we kill all of the mold and degrade all of the organic material within the coil. In infectious disease applications, air filters greater than 65% infectious disease applications, air filters greater than 65% Dust Spot are used. Not many microbes pass through them still attached to dust. Due to common filtration principals, many particles will stick. Due to these same phenomena, if and when the organism releases (unattached), it's free to absorb all the available UVC energy thus obtaining the anticipated kill. What's more, Steril-Aire disease designs are provided at 150% of the required energy. We are happy to report that those we have to date have reported no conversations to active TB.
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28. If I can't see UVC energy, what do I see?
    Greater than 95% of the energy generated by a Steril-Aire Emitter is UVC energy. The remainder is some visible light (blue hue) and a little bit of heat (infrared). Given the brightness of this "3%" visible light" gives one some idea of the amount of UVC energy a Steril-Aire product produces.

29. If I see blue it's working?
    No, the blue color comes from an inert gas in the tube and does not relate to the UVC energy produced. The tube can be lit (and blue) yet not produce any UVC energy at all. If we left out the Mercury, we would still have a blue light.

30. Will it kill dust mites?
    There is no evidence that UVC will kill dust mites, given an hour it probably would. However, there is no evidence that they live in ductwork.

31. If I use biocidal treated filters, do I need UVC?
    There is some evidence that live microorganisms caught by a filter treated with biocide will die away. There is also many more years of evidence that live airborne microorganisms caught by a untreated filter will die away. An exception would be some molds on a continuously damp filter characterized by an odor. However, none of this affects the growth of microorganisms on the coil and in the drain pan. Nor will it preclude the eventual buildup of organic material within the coil. In these latter and more important cases, UVC is the only continuous source control.
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32. Will it kill the mold in my ducts?
    Mold in ducts is the result of available spores (usually from the coil), nutrient, and boundary moisture. Nutrients can be reduced by using high efficiency filters. A mechanical form of dew point control can reduce available moisture. Neither of these measures will stop intermittent activity in the duct work. What can be done is to eliminate the source of spores by applying UVC. As their activity is self limiting , eliminating the source of spores will significantly reduce the ultimate activity within the ductwork.

33. How can it save energy?
    Using the Steril-Aire application methodology degrades organic build-up in coils. Two things happen: 1. The pressure drop across the coil will decline to "as built", which is on average some 28% for a coil 5 years and older. 2. The air leaving wet and dry bulbs drop significantly. The energy savings are through reduced horsepower (VAV) or increased air volume (reduced run time, including the condensing unit) and increased capacity. Reductions and increases will manifest themselves, one way or another, in some ultimate form of work. Using the Steril-Aire Life Cycle Cost program is an excellent way to calculate the effects.

34. How much can dirt affect heat transfer and where do you get that information?
    There have been published papers over the years documenting reductions in heat exchange efficiencies from 30 to 50%. Some by the major manufacturers like Trane and Carrier.

35. How do you install it in packaged rooftops?
    A new NEMA 4x (SEN) style fixture will be introduced by Steril-Aire sometime in the second quarter of 1998. This product will make the installation of Steril-Aire UVC Emitters in up to 20 ton Rooftops a very, very easy task.
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36. Can you install UVC in unit ventilators, heat pumps, fan coils and through the wall units, etc.?
    Yes. In fact these units are some of the dirtiest, most inefficient and IAQ problematic systems in existence. There are many successful installs currently and with the increased demand, Steril-Aire has begun a development project to handle coils as wide as 6'. They are slated for full introduction around mid 1998.

37. Will UVC kill 100% of all microorganisms?
    It would depend on a lot of criteria, but usually not. Though what is more important is a significant number reduction and with that goal, UVC is the perfect if not the only choice and there is no secondary contamination!

38. What's a rough installed fixture cost for mold & IAQ control?
    On average $0.25 per CFM.

39. How about replacement tubes for the same install?
    On average, $0.09 per CFM.

40. Is that too much to pay for once a year?
    In case of commercial, industrial or institutional buildings, the costs for lost heat exchange efficiency, air horsepower , coil cleaning and drain pan tablets already exceed the cost of a UVC install some 3-4 times. This excludes their labor, downtime, complaint service, absenteeism and litigation. In the home, many people pay more for antihistamines, other drugs, shots, Doctor office calls and the like than UVC by some 6-25 times, especially a severe allergy sufferer. This excludes the costs of lost system efficiencies, duct cleaning, service calls and system change-out. The replacement tubes of course are far less.
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41. Is there an inexpensive way for the homeowner to tell if it is still producing UVC?
    Not at this time, however, it is our intent to pursue this until a suitable method is found. Until then, annual relamping makes the best sense and usually in April.

42. What if I can't see mold on the coil?
    To have a visual occurrence would require hundreds of millions of microorganisms per square inch. What's more, most of what is thought to be dirt is in fact bound-up nutrient serving a host of active fungi? Also, a goodly portion of nutrient and activity is within the coil rather than on the leading edge to the first ¼" of the fins. As an example, some of the more notable UVC abated IAQ problems have occurred in rather dry climates where visible or edge microbial activity or even so called dirt was not apparent.

43. Why am I hearing more about bioaerosols now?
    Because researchers have begun to recognize them in the last five years, including the World Health Organization. The first researcher we worked with and who made the world popular is Dr. Harriet Burge with the Harvard School of Public Health. Our first encounter with her took place at an IAQ seminar in Maine in 1986 wherein we were both on the speaker list. Her contention was and is the bioaerosols account for a larger portion of our IAQ problems than commonly thought. The fact that she was right then and now is why we are in business today.

44. Why are bioaerosols such a problem now?
    There are two dominant reasons why we find more microbial activity today then in years gone by. First is time clock operation wherein A/C systems are shut down to conserve energy. This can be from 8 to 12 hours per day and usually the entire weekend. During these periods the coil and drain pans are wet or at least damp and the ambient temperatures near perfect for accelerated microbial growth. Second is VAV operation. Here the coil temperature remains at design point (cold ) while the air volume decreases. Air dew point is met throughout the plenum making water almost continuously. The ability to evaporate some of this moisture back into the airstream is severely restricted. Add system shutdown to the latter and one can visualize the potential problems.

45. What's different about your units and the ones that didn't work in the 50's and 60's?
    Conventional UVC tubes are made using one gas and a bead of mercury. In order to get this bead of mercury into a vapor state and thus produce UVC requires a specific temperature. The temperature ideally relates to a tube wall temperature of 90 degrees F. Blowing any air over the tube especially cold air removes sufficient heat to condense out the mercury reducing or eliminating UVC output. Hence the trick was to produce a plasma that was unaffected by heat removal. This required:
    • A blend of special gases
    • A thicker tube wall of higher purity quartz
    • Specially constructed tri-coil filaments
    • And a unique power supply to make it all come together.
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