Prominent Houston Hospital, 2015

The case

A prominent Houston, Texas hospital’s air handler units were covered in Aspergillus due to poor filtration and internally lined insulation. Sanuvox IL Coilclean was able to reverse clean the air handler units preventing any contamination in the hospital and saving the hospital thousands of dollars in energy due to reverse cleaning the cooling coils.

The Problem

Our distributor, The Filterman LLC, received a phone call from a prominent Houston, Texas hospital with a severe microbial problem. Aspergillus was growing on the evaporator coil, the transition ducting and the HEPA filters. The hospital was using substandard filters and were not sealing the filters to prevent air bypass. Houston summers routinely get above 100 degrees F and range up to 90% humidity. Biofilm growth in the fins of the cooling coil was preventing proper dehumidification and reducing the air handlers cooling capacity, resulting in thousands of dollars in wasted energy. 

After 4 years of poor filtration, the air handler units were covered in Aspergillus. The black internally lined insulation was completely white with mold growth. The HEPA filters began accumulating moisture due to the fouled evaporator coils further promoting mold growth and reducing the filters life.

Before: Pan is full may need to unclog drain of the biofilm accumulating

Sanuvox Customized Solution

Together with The Filterman, Sanuvox sized each evaporator coil, measured airflow, duct dimensions and recommended the Biowall 60” fixture per transition ducting and specific sizes of the IL CoilClean product based on coil dimensions for each of the air handler units throughout the hospital.


Within 4 months of Sanuvox Biowall and IL CoilClean installation, the evaporator coils began releasing biofilm that had accumulated through the fins of the coils. This biofilm reduced the efficiency of the cooling coil and restricted dehumidification of the air, which became the source of contamination. The internally lined insulation began turning black again as the mold growth was disinfected. The HEPA filters were changed and 5 years later, have still not grown mold.

Installation of a BioWall in the ducts

4 days incubation time

Tissue Paper Factory, June 2014

The case

During the manufacturing process, a very fine “paper” dust is produced. It passes though the filters of the A/C system, and then biocontaminants develop on the 12-inch deep coils and clog the fins.

The Problem

There are 3 coils in the air handler. They are all 11” thick and measure 133” x 108” each. The company decided to install UV lights on only one coil as a trial, because they did not want to invest much into something they didn’t believe in. 

The design pressure drop for the AHU is 2-2.5” wc. Pressure drop across the coil prior to washing was 5.5” wc. 

The coils were washed two weeks prior to the installation of Sanuvox IL Coil Cleaners, so the surface debris that are shown in the pictures were removed. Pressure drop across the coil after power washing was unchanged at 5.5” wc.

Client tentative of chemical cleaning

Layout of the coils

The plate from the downstream side of the non-UV coil isn’t much worse than the coil with UV. Because of the coil layout, the downstream side of the non-UV coil was getting some residual exposure from the adjoining coil with UV. When looking at the coil layout, the ILs were mounted on the left side coil and the non-UV samples were taken from the center coil.

Sanuvox Customized Solution

Because of the thickness of the coil, Sanuvox supplied 4 IL 60” units installed upstream and 8 IL 60’’ units installed downstream. The UV lights were operated for 3 weeks and the coil washed again. 

5 days later, pressure drop was 4.2” wc., a drop of 24%. 

Sanuvox treated one third of the coil area in this air handler and the company saw an improvement in airflow that couldn’t be achieved with washing all three coils four times a year.


Solely based on the pressure drop reduction from 5.5” to 4.2”, the fan horsepower reduction for a flow of 150,000 CFM at an electrical cost of $0.05/kWh results in annual savings of $10,000.

From previous experience, the savings in heat transfer energy is usually far greater than the pressure drop energy savings. At this moment, we do not have enough information on the operation of the coils to make valid estimates.

UAI Management LLC, October 2007

The case

UAI Management LLC purchased the SunTrust building on Lincoln Road in Miami Beach three years ago.

They wanted to make sure that the building’s air-handling system produced and circulated clean, fresh air, and operated at peak efficiency. But the assistant property manager and chief engineer quickly realized that there were problems with its filters and coil.


The Problem

The old Roll-O-Matic filter system with an oil base that was located on the roof of the building was very dirty, and the A/C coil was moldy as well. 

Although tenants didn’t complain because they had probably gotten used to poor IAQ, the air inside the SunTrust building never seemed quite right. There was a slight musty odor and the dust was everywhere. The coil and filters were cleaned twice a year, but it wouldn’t be long before mold would reappear.

IL Coil Cleaners mounted near / facing the coil.

Sanuvox Customized Solution

A series of high-performance filters would take away the airborne contaminants, but only UV would eliminate mold, bacteria and spores. Sanuvox Technologies recommended the installation of IL Coil Cleaners that shine on the coil 24/7, destroying bacteria, viruses, mold, chemicals, and their associated odors.

Sanuvox partnered with The Filtration Group, a filter manufacturer, and A-One Filters, which installs systems, to design a two-pronged strategy of treating the coil with the UV air purification technology and capturing the particulates with a series of energy-efficient filters. 

After sizing calculation, Sanuvox was able to determine the number of UV lamps that would be required for the system as well as the owner’s return on investment. This system would require five rows of four 40’’ UV IL CoilClean in line UV lamps, which were installed from top to bottom in front of the return side of the coil.


Tenants thanked the assistant property manager for being able to breathe cleaner air.

Because innovative technologies were used, the building earned not only LEED® certification but also won a prestigious national award for creating a cleaner, healthier indoor environment.

Plastic & Foam Factory, October 2017

The case

Removing odors from a manufacturing operation that slices up old plastic and foam (used material), which is then formed into sheets and used for underpadding for artificial turf installations.

The Problem

In the process of slicing up the plastics and foam, ammonia is generated. So, the manufacturer had to vent the area to remove the
smell of ammonia. In the winter months, this was going to require two make up air units to maintain the temperature in the area.

Plastic & Foam Factory

Quattro UV Air Purification Unit

Sanuvox Customized Solution

Sanuvox incorporated an air handler and a QUATTRO-GX4 to eliminate the odors, therefore eliminating the necessity for a make up air system.


The manufacturer saved about $20,000 in additional heating costs.

Cannabis Producer in Rigaud, May 2018

The case

This grower has 3 grow rooms in which he produces cannabis. The air system in each room is 5 tons (2,000 cfm). There are also fans all over the peripheral of the rooms to move the air around.

The Problem

Production was always infected with powdery mildew, botrytis and fusarium. These spores would spread on a few plants, therefore contaminating the rest of the plants through air flow.
It was becoming an issue with profitability, as the infected cannabis plants had to be discarded of.

Indoor Cannabis Facility


GC-Quattro UV Air Purifier

Sanuvox Customized Solution

After sizing calculation, it was proposed to install a GC QUATTRO unit in each return of each air handler. Because one of the owners was an HVAC contractor, the installation was a pretty simple task. Low maintenance of the units was also considered. In between production, the rooms were cleaned thoroughly, and the fans blades disinfected from all the dust settlings.


Two months later, the owner reported a full harvest in his 3 rooms, with almost no powdery mildew. He also noticed that all the fans alongside the walls no longer contained a sticky film build up on the blades. So they no longer require to be wiped down with alcohol.

The grower has launched a new larger facility in the northern part of Ontario: every unit will be equipped with SANUVOX technologies.

Effect of Germicidal UV on Plastic Materials

Effect of Germicidal UV on Plastic Materials

By Normand Brais, P.Eng., M.A.Sc., Ph.D.


Much of the effect of sunlight on materials has been attributed to the UV component (IESNA 2000), UV can fade some wall paints, wallpapers, and drapery fabrics (GE 1950). Some materials may have high UV reflectivity, like aluminum, or have high transmissivity, like quartz which absorbs very little UV. The absorption of UV by itself, is not necessarily an indicator that UV damage may occur, since it is the photochemistry which determines material effects. The total absorption is, therefore, an indicator of the potential for photodegradation in materials, while reflectivity can indicate protective effects.

UV photons energy vs. chemical bonds

When polymers are exposed to ultraviolet light, i.e. 100–400 nm wavelength, the photons energy exceeds the bond energy of the carbon bonds in the polymer or else exceeds the activation energy of chemical reaction (Moreau and Viswanathan 1976). The depth to which ultraviolet light penetrates the polymer creates a region of absorption where photochemical reaction may take place, and where photodegradation may occur. Since UV transmissivity tends to be very low for most materials, even at millimeter thicknesses, most of the photodegradation will occur on the immediate surface of a material, to a depth of typically less than 0.01 to 0.1 millimeter. For most common polymers the depth of UV penetration is typically about 0.025 mm to 0.050 mm i.e. 25 to 50 microns.

In the photodeterioration of paints, varnishes, and textiles, the quantum yield is several order of magnitudes less than unity (Feller 1994). For the bleaching of certain dyes the quantum yield has been reported to be about 0.002, meaning a thousand photons must be absorbed before two molecules are bleached. Quantum yields as low as 0.0001 (10,000 photons per molecule) have been reported for most plastics. High quality pure plastics are relatively resistant to UV but impurities and residual solvents in low-grade plastics are mainly responsible for their quick photodegradation.

Yellowing of polymers from ultraviolet exposure tends to be concentrated on the immediate surface. Surface yellowing tends to block UV and protects the inner plastic. The fading of pigments and dyes can be evaluated in terms of the loss in concentration over time (Feller 1994). The depth of discoloration is reduced by the presence of color pigments. As the concentration of pigments increases, the depth of discoloration or fading also decreases.

Plastic properties and protection against degradation

There are as many as thirteen different properties of plastics which can be used as indicators of photodegradation, including coloration, tensile strength, elongation, hardness, degree of polymerization, infrared absorbance, etc. Experimental data indicates the response of most of these properties to extended ultraviolet exposure results in data that can be effectively modeled with exponential decay curves of one or more orders.

Materials that would darken to UV after exposure create a thin UV-proof film on the surfaces of polymers like PVC. This would enable them to develop resistance to further UV exposure (Owen 1976).

The photochemical degradation of materials is a dose-dependent function that depends only on the quantum yield and the molar absorption coefficient at the irradiation wavelength (Bolton and Stefan 2002). It describes the susceptibility of a material to degrade under UV exposure. Associated with this there would be some limiting distance, a film thickness or penetration depth, to which UV would penetrate.

Based on several decades of use, experience has shown that within a few exceptions, the UV induced damages tend to remain superficial and do not generally affect the structural or mechanical integrity of thick plastic components. For critical components such as exposed electrical wire direct insulation coating, it is recommended to cover the wires with aluminum tape or run the wires inside protective metallic rigid or flex conduits according to good practice and general electrical codes prescriptions. Rubbers in general such as motor belts and conduits used in the HVAC industry have proven to stand germicidal UV very well over the last 20 years of cumulated field experience.

Screens of many electronic devices can be affected by UV degradation due to the grade of plastic used and the very thin film generally used. For such devices, protection is easily achieved by installing with a simple glass window of 3 mm thickness over the screen. Transmittivity of common amorphous glass approaches zero for below 370 nm wavelength.


IESNA. 2000. Lighting Handbook: Reference & Application IESNA HB-9-2000. New York: Illumination Engineering Society of North America.

GE. 1950. Germicidal Lamps and Applications. USA: General Electric. Report nr SMA TAB: VIII-B.

Moreau W, Viswanathan N. 1976. Applications of Radiation Sensitive Polymer Systems. In: Labana SS, editor. Ultraviolet Light Induced Reactions in Polymers. Washington, DC: Ameri- can Chemical Society, pp. 107–134.

Feller RL. 1994. Accelerated Aging: Photochemical and Thermal Aspects. Institute TGC, editor.

Ann Arbor, MI: Edwards Bros.

Bolton J, Stefan M. 2002. Fundamental photochemical approach to the concepts of fluence (UV Dose) and electrical energy efficiency in photochemical degradation reactions. Res Chem Intermed 28(7–8):857–870.

Owen ED. 1976. Photodegradation of Polyvinyl chloride. In: Labana SS, editor. Ultraviolet Light Induced Reactions in Polymers. Washington, DC: American Chemical Society, pp. 208–219.

Formicary Corrosion & Biofilm Fouling of Cooling Coils

Formicary Corrosion and Biofilm Fouling of Cooling Coils

By Normand Brais, P.Eng., M.A.Sc., Ph.D.


Air conditioning is responsible for substantial electricity consumption and peak demand in most of the United States. Over the past decade, energy conservation researchers have studied air conditioning more and more. Much of this research has focused on the impact of air flow, duct leakage, and refrigerant charge level on cooling performance.

One area, which has been neglected by researchers, is fouling of evaporator and formicary corrosion. Known commonly as ant’s nest corrosion, champagne leaks, or just simply as formicary, the issue presents as a hard to detect leak within the fin pack of an evaporator coil. This tiny leak or set of leaks results in loss of system refrigerant over time. While the incidence of formicary corrosion is low nationwide, it is more prevalent in warm, humid climates found in southern portions of the United States where slimy biofilms coat the coil fins.


The tunneling action that leads to corrosion is caused by the presence of organic acids mixed with moisture on the copper tube within the fin pack. Two common acids known to cause formicary corrosion are formic and acetic acids. Certain manufacturing oils and lubricants can contain compounds that form these organic acids, but common household items can also breakdown to form formic and acetic acids. These can include building materials like formaldehyde adhesives, foam insulation, and laminates, as well as personal hygiene products like cosmetics, disinfectants, deodorizers, and cleaning solvents. To initiate corrosion, the presence of water is necessary. The corrosion rate is aggravated by the presence of mold biofilm that keeps the fins wet.


Every technician will tell you that every time they look at these coils, they are dirty with mold biofilm. A standard part of routine A/C maintenance and residential commissioning is to clean the evaporator coil with a wire brush and detergent or other cleaning chemistry, and to clean the outdoor coil of leaves and other debris. Over the last 20 years, the simple use of appropriate germicidal UV light can prevent this and keep the coil clean and free of any biofilm buildup.

The presence of mold biofilm on cooling coil acts like a water sponge that keeps the fins constantly wet and sticky, which capture and retain particulates and chemical contaminants, thus enhancing the formic acid corrosion rate. When the biofilm is eliminated with an efficient germicidal UV system, the coil is not permanently wet, does not trap and retains as much contaminants, and consequently its corrosion rate is greatly reduced.

                                                                                     Buildup of mold biofilm in lower right hand corner completely blocks air flow

Coils normally foul due to bioaerosols and other biologically active materials, which are ubiquitous in hot climates. This usually also lead to significant indoor air quality problems that can trigger respiratory allergic responses of building occupants.

                                                                        Fungal biofilm growth on a residential (Left) and commercial (Right) cooling coil

The biofilm that causes evaporator fouling and its accelerated corrosion also impacts on the cooling performance and energy efficiency. Large commercial heating and cooling coils have the same problems and are prone to the same type of fouling and consequential corrosion issues. Their lifespan can also be increased notably by using an appropriate UV germicidal system that prevents mold buildup in hot and humid climate.

The first step to take to reduce the formicary corrosion due is to prevent the formation of a biofilm of molds and fungi with an adequate germicidal UV system. Biofilm-free fins will be less susceptible to retain dusts and potentially corrosive compounds, as well as the moisture that activates the corrosion effect.


Siegel, Jeffrey, I. Walker & M. Sherman. 2002. “Dirty Air Conditioners: Energy Implications of Coil Fouling” Submitted to the 2002 ACEEE Summer Study on Energy Efficiency in Buildings.

Siegel, Jeffrey A. and W.W. Nazaroff. 2002. “Modeling Particle Deposition on HVAC Heat Exchangers.” Submitted to the Indoor Air 2002 conference.

Siegel, Jeffrey and I.S. Walker. 2001. “Deposition of Biological Aerosols on HVAC Heat Exchangers.”

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