INDOOR AIR QUALITY

UV-C INFORMATION GUIDEULTRAVIOLET GERMICIDAL LAMP

INDOOR AIR QUALITY

Enjoy Cleaner, Fresher Indoor Air.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3What Is Ultraviolet-C? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Electromagnetic Spectrums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Types of UV Electromagnetic Energy. . . . . . . . . . . . . . . . . . . . . . . . . 4Absorption and Scattering Processes . . . . . . . . . . . . . . . . . . . . . . . . . 4Absorption and the Ozone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Ozone Generators as an IAQ Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5UV-C Usage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6UV-C Benefits and the IAQ Problem . . . . . . . . . . . . . . . . . . . . . . . . . . 6Identification of IAQ Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . 7Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Particles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Sources of Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Contaminant Effects on HVAC Systems . . . . . . . . . . . . . . . . . . . . . . . 8Solutions for HVAC Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Ultraviolet Germicidal Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Return Air Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Biofilm Source Control - Methods and Benefits. . . . . . . . . . . . . . . . 11Other Methods for Bioaerosol Control . . . . . . . . . . . . . . . . . . . . . . . 12Bryant UV-C Germicidal Lamp vs. Other UV-C Lamps . . . . . . . . . 12Continuous Treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Protecting Man-Made (Plastic) Materials from UV-C Energy . . . . 13Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Table of Contents

3

One of the most significant issues for today’sHVAC (Heating,Ventilation, and Air Conditioning)engineer is Indoor Air Quality (IAQ). Many buildingowners, operators, and occupants complain of foulodors emanating from HVAC systems.

The objectionable odor is the byproduct of themicrobial growth (mold and fungus) that accumu-lates and develops on wet surfaces of HVAC units,causing foul odors to emanate from affected systemsand degrading the IAQ and unit performance.

This objectionable odor has been appropriatelynamed the “Dirty Sock” syndrome.

Less obvious to the building occupants, but ofequal importance, are the physical effects themicrobial organisms have on HVAC equipment.They restrict the airflow and limit the heat transfercapability, which increases the operating costs ofthe equipment.

Fortunately, IAQ degradation, foul odor, andincreased expenses can be eliminated with theinstallation of the ultraviolet ‘C’ band (UV-C)lamps. The ultraviolet germicidal lamps aredesigned to kill odor causing mold and fungusthat grow in wet evaporator sections of HVACunits. These lamps are installed inside HVAC sys-tems and irradiate areas inhabited by the offend-ing organisms, making it impossible for them tosurvive. The organisms disappear, the odorsdisappear, and most importantly, the IAQ com-plaints disappear.

This guide will discuss the microbial growth andIAQ contaminant problems in the HVAC industry,the UV-C lamp and other possible solutions, andthe benefits of using Bryant’s UV-C lamp.

INTRODUCTION

Ultraviolet-C (UV-C) is one form of electromagneticenergy produced naturally by the sun. Artificiallyproduced UV-C energy aids in enhancing IndoorAir Quality (IAQ) by eliminating microbial organ-isms that grow on wet surfaces of HVAC systems.

Electromagnetic SpectrumsThe sun, a thermonuclear reactor system,

produces a spectrum of electromagnetic energywhich ranges from cosmic rays to radio waves.We are casually aware of portions of this electromagnetic spectrum, such as the infraredportion, which warms the earth, and the visiblelight portion to which our eyes respond allowingus to see. Ultraviolet energy is also a portion ofthe sun’s electromagnetic spectrum. The UVregion (excluding vacuum UV) is defined as thatportion of the electromagnetic spectrum withwavelengths between 200 and 400 nanometers(nm). UV-C, also known as “Short Wave UV,” haswavelengths of between 200 nm and 290 nm (Fig. 1).

FIG. 1 — SOLAR ENERGY

Types of UV Electromagnetic Energy The use of various forms of UV energy is quite

common in our everyday lives, some of whichrequire special care when used since they can bepotentially harmful. It is therefore important to befamiliar with these forms of UV energy, their uses,and their dangerous effects on humans when nothandled properly. Three forms of UV energy arediscussed below.

UV-A energy is the primary energy componentused in tanning beds. UV-B energy is used as atreatment for skin conditions such as psoriasis.Prolonged exposure to UV-A and UV-B energycan lead to skin cancer and has been shown tocontribute to the incidence of cataracts.1 UV-Cenergy, when used with the proper safeguards, isrelatively harmless to humans, although prolongedexposure may cause temporary reddening of theskin and/or temporary conjunctivitis.

Absorption and Scattering ProcessesAs stated previously, the sun emits a variety of

energy forms, some forms of which are harmful tothe complex molecules necessary for earth’s life-forms. The harmful forms are the ultra short-waveradiation that includes X-rays, gamma rays, andultraviolet radiation. Due to the distance betweenthe earth and the sun, only some of the energyemitted by the sun reaches the earth’s surface,minimizing the intensity of harmful particle radiation.Fortunately, the distance is appropriate for theinfrared and visible light necessary for photosyn-thesis and life as we know it.

Solar energy that reaches the earth’s atmosphereinteracts with the molecules in the atmosphere bythe processes of absorption and scattering. In theprocess of absorption, molecules absorb the solarenergy and convert it to heat. In the scatteringprocess, solar energy is reflected by gas molecules,dust particles, and water vapor. The blue color ofthe sky is due to the scattering process. Shorterwavelength (blue) light is scattered more effectivelythan the longer wavelengths, making the sky appearblue. Figure 2 compares the amount of solar energyreaching the earth’s atmosphere to the amountthat actually penetrates to the earth’s surface.

4

WHAT IS ULTRAVIOLET-C?

Absorption and the OzoneThe ultraviolet radiation that reaches the upper

atmosphere is also impacted by the absorptionprocess. A key component in absorption of ultravioletenergy is ozone (O3) in the upper atmosphere.Oxygen (O2 ) from the upper atmosphere absorbsultraviolet energy with a wavelength less than 242nm (UV-C and Vacuum UV). The result is the disassociation of the O2 molecule, allowing the formation O3 . The O3 in turn absorbs ultravioletenergy with wavelengths 242 nm to 320 nm (UV-Cand UV-B) converting the O3 back to O2 and O. Thiscontinual process limits the amount of potentiallydamaging ultraviolet energy reaching the earth’ssurface to very low levels.

It is therefore very important to maintain the ozonelayer in the upper atmosphere. In order to preserveour environment, including the O3 in the upperatmosphere and its beneficial effects, Bryant Heatingand Cooling Systems and others have significantlyreduced the use of ozone depleting compounds.

Ozone Generators as an IAQ Tool Although ozone is a very valuable component in

the upper atmosphere, it is considered a pollutantat ground level. According to the United StatesEnvironmental Protection Agency 2 “When inhaled,ozone can damage the lungs. Relatively low amountscan cause chest pain, coughing, shortness of breath,and throat irritation. Ozone is a toxic gas with vastlydifferent chemical and toxicological propertiesthan oxygen. Available scientific evidence showsthat at concentrations that do not exceed publichealth standards, ozone has little potential to removeindoor air contaminants.” Ozone belongs in theupper atmosphere, not in our homes and offices.

5

FIG. 2 — SOLAR RADIATION ENTERING EARTH’S ATMOSPHERE AND REACHING ITS SURFACE

When ultraviolet light is used on the earth’s surfacecorrectly and with appropriate safeguards, it canbe extremely beneficial as a germicidal tool. Thegermicidal effects of ultraviolet light were firstnoticed and actively studied by a Danish physician,Niels Ryberg Finsen (1860-1904), in the 1880’s.Dr. Finsen had noticed a connection betweenexposure to the sun’s rays and a stimulating effecton human tissue. His work lead to the developmentof the Finsen curative lamp, a device that producesartificial “sunlight.” This “sunlight” also containedUV light. The Finsen curative lamp remained inuse as a healing aid through the 1950’s (Fig. 3).The key portion of Dr. Finsen’s discovery was thatultraviolet light, has the ability to destroy pathogenicorganisms.3 The importance of Dr. Finsen’s workwas recognized in 1903 when he was awarded theNobel Prize for Medicine.

FIG. 3 — FINSEN CURATIVE LAMP

Today, we recognize that ultraviolet light, specificallyUV-C with a wavelength of approximately 260 nm,has a pronounced germicidal effect. We have alsolearned that mercury has a natural spectral line of253.7 nm and if vaporized in plasma, will emit UV-Cenergy at approximately 254 nm. These discoverieslead to the development of the first commercialUV-C germicidal lamps by the lamp division ofWestinghouse in the 1930’s. The Westinghouselamps were used primarily in hospital environmentsthrough the 1950’s. The challenge today is to utilize the germicidal capability of UV-C energy inthe HVAC industry.

UV-C Benefits and the IAQ ProblemTo fully understand the potential for UV-C energy

as a tool in the IAQ struggle, it is appropriate tobriefly examine the IAQ issue and the attempts todefine “quality air.” ASHRAE standard 62-1989(Fig. 4) defines quality air as, “Air in which thereare no known contaminants at harmful concentra-tions as determined by cognizant authorities andwith which a substantial majority (80% or more) ofthe people exposed do not express dissatisfaction.” 4

FIG. 4 — ASHRAE STANDARDS

A synonym for “quality air” may be “fresh air.”Fresh air is sometimes considered to be synony-mous with outside air. Outside air, dependent uponthe location, may vary considerably from theaccepted chemical composition for fresh air. Toadd further complexity, the air supplied by the HVACsystem, i.e., supply air, is typically a mix of outsideair and air returned from the conditioned space, i.e.,return air. The key point is that indoor air is com-prised of air from many sources and the determi-nation of the quality of the air is very subjective.

As difficult as it may be to quantify quality air, thereseems to be some agreement as to what constitutesan IAQ problem. In all situations where IAQ isdeemed a problem, three factors are present: asource of contamination, susceptible occupants, anda mechanism to transport the contaminants.Examples of sources of contamination are the build-ing, its furnishings, its occupants, and the outdoors.The susceptible occupants are individuals occupyingthe building and the transport mechanism is theHVAC system that circulates large volumes of air.

The IAQ problem is analogous to a three-leggedstool with the three legs of the stool representingeach of the three factors of the IAQ problem.Remove any one leg of the stool, the stool collapses,and the IAQ problem disappears.

6

UV-C USAGE

Contaminants may be categorized as gases or particles.

GasesThe gases include volatile organic compounds,

(VOCs). Organic compounds classified as alde-hyde compounds generally represent a prominentfraction of the VOCs presence. Formaldehyde andacetaldehyde are commonly recognized aldehydevapors. Potential VOC sources are off-gassingfrom the building furnishings, e.g., carpets,furniture, etc., and life cycle byproducts ofmicroorganisms living in the building (or itsHVAC system). Aldehydes are typical byproductsof both off-gassing and chemical processes, whichoccur inside or outside of the building. VOCs areparticularly concerning because many peopleexhibit reactions even when the VOC levels arebelow established permissible exposure levels(PEL). The most common symptoms related to VOCsensitivity are irritation of the eyes, nose, or throat.

ParticlesThe classification of a contaminant as a particle

or a large molecule can sometimes be difficult. Wecan arbitrarily define a particle as any species witha diameter of 0.1 micrometer or greater, whereaslarge molecules are less than 0.1 micrometer indiameter. Viruses, for example, range in size fromabout 0.05 micrometers to slightly larger than 0.1micrometers, and viruses are popularly referredto as particles. Bioaerosols are defined as airborneparticles, which are living organisms, spores, orfragments of organisms released from livingorganisms. The bioaerosols include pathogens(disease causing viruses, fungi [mold], and bacteria),allergens (fungi [mold] and bacterin which initiateallergic reactions), and toxins (mycotoxins andendotoxins). Aerodynamically, the bioaerosolstend to behave like gases, i.e., they float in the air,are induced to move by thermal gradients, andmay remain suspended for hours.

Where do these bioaerosols come from?Unfortunately, modern buildings provide a havenfor them. The fungi will propagate in dark,damp areas, requiring a relative humidity of only30% or greater. A visual indicator of the presence

of fungi is mold. Mold is a byproduct of the fungiand is typified by a green/gray color and a mustysmell. Bacteria are most likely to flourish in standingwater and have been known to exhibit the dirtysock odor. Humans also contribute bioaerosols tothe atmosphere. Sneezing and nose blowing arethe major sources of aerosolized viruses in a building.A single sneeze may produce 100,000 pathogen-containing droplets of moisture.5 These droplets,known as “Fomites”, will remain suspended forlengthy periods of time and are circulated by theHVAC system.

In short, the types of contaminants are diverseand come from a multitude of sources. The com-mon factor with all of these contaminants is thatsome may be circulated by the HVAC system.

Sources of ContaminationOf particular concern is the contamination of the

HVAC system with bioaerosols. The requisiteneeds for biological contamination are a source ofwater, a nutrient base, and an initial seeding ofbioaerosols. The number of bioaerosols requiredfor contamination may be very small; in fact only amicroscopic quantity is needed. The sources ofthese bioaerosols may be external to the buildingor from within the building itself. Bioaerosolsenter the HVAC system through its air intakes.Various forms of fungi exist outdoors and typicallyenter the HVAC system through the fresh airintakes in the form of spores. The spores are veryhardy and may lie dormant for long periods oftime waiting to flourish under the proper environ-mental conditions. The indoor environment, whichis warm and protected from sunlight, createsan environmental niche for viruses and bacteriathat could not otherwise survive for long out-doors. The spores propagate releasing additionalspores to the interior environment creating whatis known as the Amplifying Effect. It is not uncom-mon for the number of spores in the return air toexceed the outdoor levels.

7

IDENTIFICATION OF IAQ CONTAMINANTS

Small animals, rodents, and birds can transport adiverse mix of environmental bacteria and variouspathogenic organisms to the HVAC systemthrough the return air stream.

Climactic conditions are also a factor in HVACsystem contamination. Fungi exist virtually every-where but are especially abundant in hot climates.When the soil is dry, windy conditions will readilydisturb the soil, and the air currents will carry thespores and bacteria to the HVAC intakes.

Today’s HVAC operating conditions may alsocontribute to the level of contamination. Prior tothe energy crisis of the mid 1970’s, the typicalHVAC system operated continuously with con-stant airflow. Moisture, which condensed on thecoil and flowed to the drain pan, would reevapo-rate in the constantly moving air. As a result, thecoil surfaces and drain pan remained dry most ofthe time. Post energy crisis operation haschanged to one in which the airflow is variablethrough the use of variable air volume (VAV) sys-tems, timeclocks that cycle the units ON/OFF,and variable frequency drives (VFDs) that varythe fan speed. The variable airflow allows the coiland drain pan to collect moisture, providing anideal growth environment (dark, warm, andmoist) for fungi, bacteria, and viruses.

In the past, coil and drain pan cleaning may havebeen performed as often as once a week. Today,according to the Building Owners and ManagersAssociation (BOMA), the average cleaning is only3.5 times per year. The change in operating meth-ods combined with the changes in maintenancepractices have resulted in a man-made environ-mental niche that supports the growth ofbioaerosols. This niche is the perfect breedingground for bioaerosols. An average cell divisionrate for molds and bacteria is once every 120 min-utes. At this rate, a single organism deposited onthe damp, warm coil could multiply to 5.7 X 10 17

(570,000,000,000,000,000) organisms in one week!

Contaminant Effects on HVAC SystemsThe effects on the HVAC system are twofold.

The first is performance degradation. The millionsof organisms that grow on the coil surface restrictthe airflow through the coil resulting in decreasedequipment performance and higher operatingcosts. The organisms on the fin surfaces alsoreduce the heat transfer capability of the coil,resulting in decreased performance and higheroperating costs.

The second effect is on indoor air quality. Fungi,bacteria, and viruses are flourishing in this man-made niche. When the HVAC system is operating,the large volumes of air moving throughout thestructure carry these bioaerosols into every section of the building. The HVAC system hasbecome a host and an amplifying factor for a“source” in the IAQ problem.

Solutions for HVAC ContaminantsFortunately the solution is simple. Utilize ultraviolet

germicidal irradiation (UVGI) to kill contaminantsin the HVAC system. Install man-made sources ofUV-C energy in the HVAC system to help eliminate a“source”, and the IAQ three-legged stool collapses.

8

UV-C energy when applied in the proper mannerhas the ability to prevent biological growth. UV-Cenergy is capable of breaking molecular bondsdisrupting the cellular growth of the target organ-ism.6 UV-C energy alters the DNA of the organism,preventing reproduction and multiplication.The key to UVGI is to apply a chronic dose ofultraviolet energy that kills 99.9% of the targetorganism(s).

The output of an UV-C lamp is expressed inmicrowatts/cm2 measured at a distance of onemeter from the bulb. To evaluate the outputenergy at distances different than 1 meter, the“intensity factor” is used.7 The Intensity FactorCalculation table below depicts how the distancefrom the lamp to the target determines the intensity factor.

INTENSITY FACTOR CALCULATION CHART

The dose applied by an UV-C lamp installation isa function of the lamp output, the intensity factor,and time. The equation may be stated as:

Dose = Lamp output at 1 meter (Microwatts/cm2)x Intensity Factor x Time (sec.)

The dose required to kill a given microorganismis given in units of microwatt-seconds/cm 2.Figure 5 details the dose required for disinfection(90% kill) and sterilization (99.9% kill) for a varietyof common mold spores (fungi).8, 9, 10, 11

FIG. 5 — UV-C DOSAGE REQUIREMENTS

The time required to kill 99.9% of a given organ-ism is expressed by the formula:

Time = Required Dosage / (Lamp Output at 1meter x Intensity Factor)

Figure 6 indicates the time required for steriliza-tion of Penicillium expansum, one of the mostcommon indoor spores, when the lamp is placed 8inches away from the target.

FIG. 6 — UV-C TIME REQUIREMENTS CHART

9

ULTRAVIOLET GERMICIDAL IRRADIATION

Time = Required Dosage / (Lamp Output xIntensity Factor)

Time = 22,000 Microwatt sec/cm2/ (120Microwatt/cm2 x 9.85)Time = 18.6 secondsIn 18.6 seconds, 99.9% of the Penicillium expansumorganisms will be dead.

The next question is how do we best utilize thispotent UV-C energy to apply a fatal dose to thesebiological contaminants?

Since UV-C energy requires a finite amount oftime to effect a kill, it’s ideally suited to treat staticcontaminated surfaces - like the damp evaporatorcoil and condensate pan inside an HVAC unit. Oneof the best locations for the Bryant UV-C germicidallamps is on the leaving air side of the evaporatorcoil over the condensate pan so that both areasare irradiated simultaneously. HVAC units usingevaporator coils that are very deep may requirelamps installed on both sides of the coil for besteffectiveness. In either case, following the sizingguidelines appearing later in this guide will assuremore than enough UV-C dosage to sterilize thetarget area.

Return Air ApplicationsAttempting to treat “fly-by” contaminants enter-

ing the HVAC unit from either the return air sys-tem or ventilation air is not practical with currenttechnology. The problem with “fly-by” control isthe time required to affect a kill and the distancetraveled by the contaminant in that time period.Consider the foregoing example of Penicilliumexpansum. If the air in the ductwork is traveling at400 ft per minute, in 18.6 seconds the targetorganism will have traveled 124 feet. This means,at the flux density of the Bryant UV-C germicidallamp, a bank of UV-C lamps 124 feet long wouldbe required to affect a 99.9% kill. Obviously this isnot practical at this time.

10

One of the most beneficial uses of UV-C lamps inan HVAC system is as a surface treatment device.This method is called “biofilm source control.” Inthis application, the bioaerosols on the evaporatorcoil or in the drain pan will be killed at the source.Therefore, the offending bioaerosol will not havethe opportunity to enter the ducts, the terminaldevices, or the building itself. Installation of UV-Clamps in new systems will ensure that the per-formance loss associated with bioaerosol contami-nation of the coil and drain pan cannot occur. Inexisting systems, the performance impact of thebioaerosols will be reversed and eventually elimi-nated. The irradiation of the coil surface and drainpan will ultimately kill all of the organisms. Theorganisms will decay and be carried away in thecondensate water. Initially the UV-C energy willkill the organisms on the surface. In the case ofthe coil, as the organisms disappear from the sur-face, the UV-C energy will be able to reach deeperand deeper into the coil, reflecting from fin to fin,ultimately destroying the organisms throughoutthe coil. In the case of the drain pan, if standingwater exists, the UV-C energy will kill the organ-isms at or near the surface of the water first. TheUV-C energy will not penetrate below the surfaceof the water, but over a period of time movementof the organisms in the water will cause the organ-isms to move to the surface and be killed. Thetypical result is a return of the coil and conden-sate pan to an “as installed” condition. Coil pres-sure drop typically will also return to “as installed”levels (excluding losses due to normal systemaging) with the accompanying reduction in fanenergy requirements. Figure 7 depicts theimprovements noticed during a 30-day period fol-lowing the retrofit of a 20-year old air handler withBryant UV-C germicidal lamps.

FIG. 7 — HVAC IMPROVEMENTS WITH UV-C LAMP INSTALLED

The benefits will also be obvious in reducedmaintenance costs. The need for coil cleaning dueto the buildup of bioaerosols will be virtually elim-inated. In the presence of UV-C energy the moldwill not develop.

Other forms of coil cleaning may only clean thevisible surface of the coil. In fact, pressure wash-ing of coils may compact the “dirt” deep inside thecoil resulting in increased coil restriction. Thereflective nature of the UV-C energy allows it tokeep the coil clean from surface to surface. Drainpan restrictions are also reduced. Typical condensate

11

BIOFILM SOURCE CONTROL - METHOD AND BENEFITS

drain blockages result from what appears to be“hair.” Quite often the maintenance worker is perplexed as to the source of all of this “hair.”Once again, this “hair” is most likely mold thatcannot exist in the presence of UV-C energy.

The necessity for routine duct cleaning may alsobe reduced. Mold growing in the ductwork typi-cally develops from spores that were introducedinto the HVAC system. If the spores are killed atthe coil area, they will never have the opportunityto grow into mold. However, the installation of UV-C lamps in the evaporator section of the HVACsystem will not affect existing mold in the ducts.

The single most obvious advantage of the use ofUV-C energy in the HVAC system is the IAQimprovement perceived by the building occupants.The “Dirty Socks” odors that are typical whenbioaerosols are flourishing in the HVAC systemhave been found to disappear with the applicationof UV-C lamps. Discoloration of ceiling air ter-minals due to a buildup of mold and spores isreduced. These improvements typically occur in amatter of days. The result is that the comfort levelof the building occupants increases dramatically.Increased occupant comfort may be connected toimproved attendance and increased employee pro-ductivity. The financial benefits associated withproductivity gains and reduced needs for tempo-rary or substitute workers can be significant overtime.

Other Methods for Bioaerosol ControlCertainly there are other approaches to control

of bioaerosols in the HVAC system. However,each of these methods may have disadvantages,which UV-C energy does not have.

Chlorinated cleaning agents and biocides havebeen known to off-gas objectionable chemicalsand/or odors to the occupied space. Biocides inparticular are limited by the “Dead Body Effect.”The biocide must physically come into contactwith the target organism in order for a kill tooccur. Once a layer of “dead bodies” developsbetween the biocide and the target, the biocidemay lose its effectiveness.

High Efficiency Particulate Air (HEPA) filtrationis another alternative. HEPA filters have the abili-ty to intercept many fungal spores. However, theyalso intercept nutrients, and if damp, provide a sitefor the spores to grow and multiply. The sporesmay grow through the filter material, releasingspores on the downstream side of the filter.12

The result is that the filter contributes to theincrease in the number of spores in the occupiedspace rather than decreases them. HEPA filtersare unable to remove viruses. Typical HEPA fil-ters are designed for removal of particles 0.3microns and larger. Common viruses have a diam-eter of 0.2 microns or less. Viruses such asAdenovirus, Influenza, and Rhinovirus, which areresponsible for colds and flu, have diameters assmall as 0.02 microns. Viruses pass throughHEPA filters unimpeded. UV-C has the flexibilityand operating characteristics to suit any applica-tion without the disadvantages associated withbiocides, cleaning agents, or special filtration.

Bryant UV-C Germicidal Lamp vs. OtherUV-C Lamps

The best utilization of UV-C technology for HVACsystems is in “biofilm source control.” Use UV-Cenergy to eliminate the source of many contami-nants, thereby collapsing the IAQ three-leggedstool. For this application, downstream of the coolingcoil, the UV-C lamp must be able to provide maximum dosage of UV-C energy at 45 to 55º Ftemperatures in a rapidly moving airstream - a jobideally suited for the Bryant UV-C high output,low temperature duty germicidal lamps. It isimportant to understand that not all commerciallyavailable UV-C lamps are suitable for use in aHVAC system. Many commercially available UV-Clamps are designed for optimal performance atroom temperature and allow significant powerreduction at lower temperatures. Lamps of thistype are not suitable for use in the damp, cool,moving airstream environment found in the HVACsystem. The Bryant Heating and Cooling SystemsUV-C germicidal lamp uses a blend of inert gasesin the bulb and a specialized power supply thatmaintains the optimal plasma temperature insidethe bulb even in a low temperature, movingairstream. This combination results in a UV-C

12

13

lamp which provides its maximum power outputat 45º F and 400 fpm, perfect for use in an HVACsystem. Equally important, the mixture of gasesused creates a bulb which does not produce UVwith wave-lengths of less than 200 nanometers.Therefore the Bryant UV-C germicidal lamp doesNOT contribute to the production of ozone.

One of the key factors in providing a sterilizingdose of UV-C energy is lamp output. By providinga lamp that has its highest output at low tempera-tures, Bryant Heating and Cooling Systems UV-Cgermicidal lamps will kill the target organisms inthe shortest period of time.

Continuous TreatmentIt is recommended that the UV-C lamps are

“ON” at all times and not cycle with the fan or theHVAC system. The most opportune time forgrowth of fungi and mold is when the air is still(the fan is “OFF”); therefore it is important toirradiate the surface at all times. The energy consumed is only 70-75 watts per lamp.

Protecting Man-Made (Plastic) Materialsfrom UV-C Energy

UV-C energy does have the ability to hasten theaging process of certain man-made materials(plastics). All of the plastic components containedin the Bryant gas furnaces and fan coils have beentested and are UV resistant. In regard to plasticdrain pans used on Bryant evaporator coils, accel-erated testing of materials used in Bryant drainpans has been conducted. To date, the equivalentof many years of continuous exposure has pro-duced no damage. Some of the materials may fadeor chalk slightly but the properties of the materialsremain sound. When installing the Bryant UV-Clights on competitor furnaces of fan coils and youare not sure of the UV resistance or their compo-nents, the plastic materials should be protectedfrom the UV-C energy. This is easily accomplishedby sheilding the wiring or other components withfoil tape, metal conduit or sheet metal. A commonquestion is, “What effect will UV-C energy haveon the filters?” High efficiency, non-fiberglass fil-ters exposed to UV-C energy will be damaged.The plastic fibers in the media will not stand up tothe UV-C energy. Filters are generally locatedupstream of the coil and the Bryant UV-C lampsare designed for the downstream side of the coil.For this reason very little of the UV-C energyreaches the filter surface. When installing UV-Clights in the return air duct, select a mountinglocation that prevents direct exposure to non-fiber-glass media filters. A minimum distance of 6 feetis recommended.

UV-C energy is safe and beneficial when usedproperly. In HVAC applications the UV-C energy iscontained inside the HVAC system. In this loca-tion it does not present a potential hazard tohumans because the UV-C energy will neverreach the occupied space of the building.

A UV-C lamp has tremendous potential as anIAQ tool. It provides a low cost, simple to install,flexible method of attacking the “Dirty Socks”problem. Apply UV-C as a biofilm source controldevice and help eliminate the “source” leg of theIAQ three-legged stool. Eliminate the environmentalniche in the HVAC system that is promoting theproliferation of mold and attack one of the sourcesof the “Dirty Socks” problem. UV-C energy is amajor part of the IAQ solution.

14

SUMMARY

15

1. M. Tevini, editor: “UV-B Radiation and OzoneDepletion: Effects on humans, animals, plants,microorganisms, and materials” Lewis Publishers,Boca Raton, (1993)

2. United States Environmental Protection Agency,“Ozone Generators That Are Sold as Air Cleaners”,http://www.epa.gov/iedweb00/pubs/ozonegen.html

3. The Nobel Foundation, “Biography of NielsRyberg Finsen”, http://www.nobel.se/laurates/medicine-1903-1-bio.html

4. ASHRAE, “Ventilation for Acceptable Indoor AirQuality”, American Society of Heating, Ventilating,Refrigerating, and Air-Conditioning Engineers,Inc, Atlanta, Ga.

5. Kowalski, W.J. & Bahnfleth, W., “AirborneRespiratory Diseases and Mechanical Systems forControl of Microbes”, HPAC Heating/Piping/AirConditioning (July 1998)

6. Ultraviolet Germicidal Irradiation, AerobiologicalEngineering, The Pennsylvania State University,http://www.engr.psu.edu/ae/wjk/wjkuvgi.htm

7. Scheir, R. & Fencl, Forrest, “Using UVCTechnology to Enhance IAQ”, HPACHeating/Piping/Air Conditioning (February 1996)

8. Luckiesh, M. , Application of Germicidal,Ethyemal and Infrared Energy, D. Van Nostrand,New York, N.Y. (1946)

9. Hallaender, A. & Oliphant, J.W., Journal ofBacteriology, Volume 48, (1948)

10. Disinfection by UV-Radiation, Phillips LightingCorporation (undated) and cited references therein

11. First, M.W., Nardell, E.A., Chaisoon, W., & Riley,R., ASHRAE Transactions, Volume 105, Part 1(Chapter 99-12-1, 99-12-2) and cited references therein

12. Kowalski, W.J. & Bahnfleth, W., et al

REFERENCES

Before purchasing this appliance, please read the important energy cost and efficiency information available from your dealer.

Manufacturer reserves the right to discontinue, or change, at any time, specifications or designs without notice and without incurring obligations.

8110-285© Bryant Heating and Cooling Systems 20037310 West Morris Street, Indianapolis, IN 46231

Visit our website at www.bryant.com

A Member of the United Technologies Corporation Family.Stock Symbol UTX.