photo of corona virus
Methods of Helping Prevent the Growth and Spread of Microorganisms throughout an HVAC (Heating and Cooling) System and Improving Indoor Air Quality

With the advent of COVID-19, caused by the SARS-CoV-2 virus (coronavirus), sanitizing and cleaning of all living and work spaces and equipment has become of primary importance. Another very vital but overlooked area to keep hygienically maintained is your heating and cooling (HVAC) system, since bioaerosols (microorganisms such as viruses, mold, bacteria, fungi, etc.) can be transmitted throughout your indoor spaces by your heating and cooling system.

It is quite common for people to insist upon clean drinking water. Also, most people prefer non-GMO or organic food, or at least food that is properly cleaned of pesticides. When washing one's hands, particularly in an unsanitary environment, antimicrobial soap would be the preferred choice.

What about the air you breathe inside your home? Is it as safe as the water you drink, the food you eat and the soap you wash with?

Per the EPA, indoor air has up to 100 times the pollutants that outdoor air has. In the past, dark and damp areas of heating and cooling systems have provided a perfect breeding ground for the unchecked growth of bioaerosols (microorganisms).

Indoor air is continuously recirculated within the indoor conditioned spaces by the heating and cooling system. As this occurs, if the heating and cooling system has a proper air treatment system installed within it, this would serve as the perfect opportunity to improve indoor air quality on an ongoing basis.

Bioaerosols (microorganisms) are sometimes the source of various non-optimum physical conditions, illnesses and assorted discomforts such as tiredness; itchy, achy, watery eyes; as well as respiratory difficulties.

Air from a contaminated heating and cooling system can be the cause of allergic reactions. Using our multifaceted, thorough approach to improved indoor air quality can greatly reduce the presence and growth of bioaerosols (microorganisms such as viruses, mold, bacteria, fungi, etc.) which can create sludge within the heating and cooling system.

These microorganisms thrive in the dark, damp environment in the vicinity of the cooling coil and continually flourish around the clock to create a living, mucky, sludge which can also cause the heating and cooling system to operate inefficiently, making the system more expensive to operate and maintain.

Our equipment and filtration functions 24 hours a day, removing contaminants and cleansing the air. And our purification devices use less energy than a night light, costing less than 10 cents per day to operate.

While no air cleaning/purification system can guarantee total protection against all pollutants, our methods, as delineated here, are among the most effective in existence today.

According to the Centers for Disease Control, indoor air pollutants typically consist of three categories in the following percentages:

  1. Bioaerosols (microorganisms such as viruses, mold, bacteria, fungi, etc.), 34%;
  2. Volatile Organic Compounds (chemical gases, solvents, glues, odor causing contaminants, etc.), 31%;
  3. Particulates (dirt, dust, pollen, spores, etc.), 35%.
Indoor Air Pollutants
Indoor Air Pollutant Percentages

We have a multifaceted approach that addresses each of the above mentioned types of pollutants impacting your indoor air quality. Let's take a look at the way these processes work in simple, non-technical terms.

The first step in handling the pollutants in the heating and cooling system is a very thorough cleaning of the system using source-removal techniques (as recommended by the National Air Duct Cleaners Association) to extract existing contaminants already present within the system.

After a thorough cleaning of the existing heating and cooling system to remove the existing particulates, the bioaerosols (microorganisms) and volatile organic compounds (VOCs) should be dealt with by the installation and use of an ultraviolet (UV) high-output germicidal lamp with a photo-catalytic oxidation (PCO) air purifier.

Future particulates that accumulate on a day-to-day basis will be safeguarded against by installation of high-efficiency filters. In combination with a good filter system, a UV light/PCO air purifier can effectively eliminate pollutants to furnish breathable, clean air.

While many would like to employ an HVAC sanitizer or virucide as a COVID 19 treatment for indoor air, the only HVAC sanitizers registered with the EPA (Environmental Protection Agency) for use inside HVAC systems for sanitizing HVAC systems and HVAC ducts do not kill viruses (are not virucides).

These EPA registered sanitizers are effective as HVAC air sanitizers and HVAC coil sanitizers, but are ineffective against viruses. They are ordinarily used as air conditioning sanitizers and for sanitizing air conditioning ducts, but offer no protection from viruses.

For heating and air conditioning sanitizing and to sanitize heating ducts, we have employed an EPA registered (for use inside HVAC systems) heating and air conditioning sanitizer for years as an air conditioner sanitizer, and it works when applied directly inside HVAC systems to help mitigate odors and minor mold presence; however, it will not kill viruses in the air.

Another drawback to the sanitizers registered by the EPA for use inside HVAC systems is that, since they are chemicals, one is applying chemicals inside one's HVAC system which is then recirculated into indoor air spaces, and because of their being chemicals, these sanitizers are only recommended by the National Air Duct Cleaners Association to be used when actual mold growth is detected in the heating and air conditioning system.

There are no virucide sprays, virucide cleaners, virucide concentrates, virucide or disinfectant foggers (used for virucide fogging) or air disinfectant sprays that are registered by the EPA for use inside of HVAC systems to kill germs in the air or to disinfect air ducts. There are no "virus air filters" that can effectively prevent viruses from entering indoor conditioned spaces.

Because of the above factors, we recommend a UV light/PCO air purifying system to act as an ultraviolet (UV) HVAC sanitizer and virus air purifier to kill viruses naturally with UV light (specifically, UVC light for disinfection and as a sanitizer) in order to mitigate virus air pollution.

Per the U.S. National Institutes of Health's National Library of Medicine, National Center for Biotechnology Information, American Society for Microbiology Journal of Virology, "Sunlight or, more specifically, solar UV radiation (UV) acts as the principal natural virucide in the environment. UV radiation kills viruses by chemically modifying their genetic material, DNA and RNA."

DNA (deoxyribonucleic acid), are molecules that contain the genetic blueprint of living organisms. RNA (ribonucleic acid) are molecules that contain the data needed to create new cells and maintain life.

Ultraviolet (UV) light and photocatalytic oxidation (PCO) processes are natural virus killers and in conjunction with high-efficiency air filtration (after thoroughly cleaning the entire HVAC system), serve as the most natural approach to handling contaminants (including bioaerosols [microorganisms such as viruses, mold, bacteria, fungi, etc.], volatile organic compounds [VOCs, chemical gases, solvents, glues, odor causing contaminants, etc.] and particulates [dirt, dust, pollen, spores, etc.]) recirculated throughout the indoor air spaces.

What are ultraviolet (UV) light and photocatalytic oxidation (PCO) and how are they used to improve indoor air quality?

Ultraviolet (UV) light waves are waves that are just beyond the visible spectrum, smaller than violet light waves, which are the smallest light waves of the visible spectrum. These UV light waves are of the same character as those that are constantly emitted by the sun at all times.

The process used is called ultraviolet germicidal sterilization and employs UV light waves with short enough wavelengths (253.7 nanometers [253.7 billionths of a meter]) to decompose microorganisms (UVC light waves for disinfecting).

Can UV (UVC) light kill coronavirus? Per, "...ultraviolet light in the 'C' range, also known as UVC, has been shown to kill SARS-CoV-2, the virus that causes COVID-19.... Of the three main types of UV light, UVC (which has a wavelength range of 200 to 280 nm) is the most effective for inactivating viruses...."

Bioaerosols (airborne microorganisms like viruses, mold, pathogens, etc.) typically flourish in heating and cooling systems and utilizing a UV air purification system can be quite effective at killing these microorganisms.

Petri Dishes
The Petri dish on the left was exposed to UV germicidal sterilization lamp for 72 hours and the Petri dish on the right was exposed to the same indoor air without UV germicidal sterilization.

Photo = light, catalytic = speeding up a process, oxidation = combine with oxygen so as to break up (decompose) organic molecules. So photocatalytic oxidation (PCO) means using light to speed up the process of combining (something, in this case pollutants) with oxygen so as to eliminate them.

Advanced nanotechnology is used inside the heating and cooling system so that a UV high-output germicidal lamp's light in conjunction with the moisture in the air forms oxygen on the photocatalytic oxidizer's surface in order to combine with and break down pollutants, such as viruses, pungent odors, toxic materials and allergens by this oxidation process.

Our UV high-output germicidal lamp in combination with our photocatalytic oxidizer (PCO) keeps pollutants from entering conditioned spaces, such as indoor living and working environments. This combination breaks down the source of odors and purifies the air circulating in the indoor environment year-round, helping improve indoor air quality.

Airborne pathogens such as viruses, bacteria, mold, etc., as well as pet dander, musty odors, etc., are acted upon by this combination (UV light + PCO) to help mitigate them.

Volatile organic compounds (VOCs, chemical gases, solvents, glues, odor causing contaminants, etc.) are removed to a great extent as the air circulating through the heating and cooling system over and over is cleaned and sanitized while also continually killing viruses and mold (bioaerosols), and helping to remove odors from the entire indoor living or working environment on an ongoing basis.

Indoor odors have many origins, including carpets, furniture, paint, smoke from cooking, cigarette smoke, household cleaners, dry cleaned items, pesticides, etc., and when these odors in the air are drawn into the heating and cooling system, they are acted upon by the photocatalytic chamber (UV high-output germicidal lamp and photocatalytic oxidizer [PCO]).

Two professors in Tokyo discovered PCO technology in 1969 and found that it speeds up the organic matter's natural decaying process. Although new in America, PCO technology is now being used to purify air and water, and is also approved by the FDA for processing pork and poultry to curtail bacteria and to clean fruits and vegetables to remove pesticide residues. It is a powerful, green solution, and is effective on any contaminants that are organic.

Our method entails placing a specialized UV high-output germicidal lamp with a photocatalytic chamber inside the heating/air conditioning system, typically in the cooling coil and supply/return plenum area(s), to work continuously, day and night to mitigate bioaerosols, such as viruses, mold, bacteria, fungi, and volatile organic compounds (VOCs, chemical gases, solvents, glues, odor causing contaminants, etc.) from the system, generating UV waves that are more than 800 times the intensity of the sun's waves.

UV Disinfection
Typical UV Light/PCO Air Purifier Installation Locations

The germicidal lamp is the brightest and strongest of those currently on the market and effectively cleanses the air passing under it. It does this by breaking down and wiping out active DNA growth, including viruses, mold, mildew, bacteria, fungi and their odors, and also helps keep the cooling coil clean and efficient to save energy.

This UV system is effective at all temperature ranges within the heating and cooling system, from very cold to very hot. The high-output germicidal lamp continuously shines upon these moving particles and has a high kill ratio over a wide range of microorganisms.

This is a low maintenance method of treating the air in heating and cooling systems. UV technology has demonstrated its effectiveness over the years and has been safely employed for over 75 years in a number of different settings, from medical/dental offices and hospitals to food manufacturing facilities, and has also been being safely used in homes and general businesses for more than 20 years.

This UV/PCO system (air purification/disinfection system/device/machine to purify indoor air naturally) can greatly improve the indoor air quality of residential and commercial environments and easily fits heating and cooling systems. It removes from the air stream most unpleasant smells, volatile organic compounds (VOCs) and chemical irritants safely.

For air purifying (as an air disinfectant), the UV light/PCO air purifying system is without peer when used to purify the air in homes and commercial/industrial applications in order to disinfect room air.

Air to be purified is drawn into the photocatalytic chamber of the photocatalytic oxidation (PCO) air purifier. The photocatalytic chamber is composed of a UV high-output germicidal bulb encompassed by a titanium dioxide catalyst.

When the ultraviolet light shines upon the catalyst, it bombards the chemical bonds of the bioaerosols and transforms these toxins into harmless components (water [H2O] and carbon dioxide [CO2], which is what is exhaled when breathing).

In other words, the UV light has a reaction with the titanium dioxide surface which, with moisture in the air, forms hydroxyl radicals (one atom of hydrogen bound to one atom of oxygen, known as the "planet's detergent" because of their reaction with many contaminants) and oxidizers (substances that combine pollutants with oxygen to decompose them) to kill harmful bioaerosols (airborne microorganisms) and decompose airborne chemicals which are always moving through the indoor air and change them into benign water (which evaporates immediately) and carbon dioxide.

Hydroxyl radicals are four times more powerful than chlorine and 1-1/2 times stronger than ozone in terms of ability to decompose organic material.

These hydroxyl radicals are quite efficacious at attacking and destroying all organic matter close to them, including viruses, fungi, bacteria, cigarette odors, as well as VOCs (volatile organic compounds) commonplace in homes and commercial establishments, such as acetone, formaldehyde (found in in glues, wood products, preservatives, permanent press fabrics, paper product coatings, certain insulation materials, particle board, fiberboard in cabinets and furniture, plywood wall panels, and foam insulation), chlorinated solvents, hydrocarbons, exhaust fumes, benzene, toluene, ammonia, hydrogen sulfide (found in petroleum, natural gas and sometimes in ground water), carbon monoxide and nitrous oxide, etc.

UV Diagram

This process occurs in Nanoseconds (billionths of a second) and keeps on occurring while UV light, air moisture and titanium dioxide are there. Since the hydroxyl radicals have a half-life of Nanoseconds (not even measurable by precise laboratory methods), they do not exist long enough to move through the air and will not enter or build up in indoor occupied areas the way that ozone (which has a half-life of days) can. So UV light/PCO air purifying systems leave nothing behind the way other purifying methods do.

The titanium dioxide remains on the chamber's surface and never diminishes. Titanium dioxide is a combining of the metal titanium with oxygen and is found naturally amongst various rocks and in sands at the beach. It is the ninth most frequently occurring mineral on the planet, is an ingredient in foods, cosmetics, toothpaste, etc. and is FDA classified as “Generally Recognized as Safe”.

When placed correctly inside a heating and cooling system, the titanium dioxide in combination with the UV light waves destroy VOCs, viruses, mold, influenza, anthrax, allergens such as pollen, etc., and can eliminate particles as small as .001 microns (HEPA filters filter particles .3 microns and above).

Indoor air is pulled in through the return vent and goes through the UV light/PCO air purifying system and emanates as purified air through the supply vents.

Formaldehyde and hydrogen sulfide are two of the most common volatile organic compounds (VOCs) and both are carcinogenic.

Formaldehyde exposure can cause skin rashes; watery eyes; wheezing; burning in eyes, nose and throat; chest tightness; coughing; nausea; and can also cause cancer in humans and animals.

Hydrogen sulfide can cause poisoning from inhaling it and is as poisonous as cyanide. It can disable the sense of smell, cause headaches, eye irritation, coughing and dizziness, and in high amounts, can paralyze the lungs and lead to death.

Both formaldehyde and hydrogen sulfide are broken down and decomposed by the UV light/PCO air purifier.

Any living organism with DNA is killed with sufficient amounts of UV light over time as it continually acts upon it. So when indoor air recirculates through the heating and cooling system with a UV light/PCO air purifying system, it is constantly disinfected.

If a bioaerosol (airborne microorganism) does not get killed when it is first drawn through the HVAC system, its DNA will decompose more and more as it recirculates through the heating and cooling system. Bioaerosols continue to reproduce if not mitigated.

UV light/PCO air purifying systems assist in lessening the exposure through inhalation to bioaerosols in indoor environments whose heating and cooling systems have these air purifiers installed.

UV Cleanser
Photocatalytic oxidation (PCO) air purifier with ultraviolet (UV) high-output germicidal lamp for indoor heating/AC units. This unit carries a limited, lifetime warranty.
                 oxidation air purifier
Photocatalytic oxidation (PCO) air purifier with ultraviolet (UV) high-output germicidal lamp for outdoor heating/AC units. This unit also carries a limited, lifetime warranty.

This UV light/PCO air purifying system has maximum UV output and is listed with Underwriters Laboratories for safety. The PCO chamber never needs to be cleaned or replaced. It gets rid of most smells generated by pollutants and uses no ozone (with its harmful off-gassing).

This is a more natural, greener air purification method than the ozone (which puts out harmful off-gassing) purifiers on the market today, is very conducive to bringing about higher indoor air quality and a fresher breathing environment and can be installed into any heating and cooling system.

Photocatalytic oxidation (PCO) technology has been tested and proven over time and occurs when ultraviolet light rays are combined with a titanium oxide coated surface.

Third party tests have been conducted domestically and abroad that prove that PCO technology greatly lowers the presence of smoke, smells, kills microorganisms and helps remedy surface contamination.

There is no need to worry about our technicians causing contamination while working on or in your home or work areas. Optimum Indoor Air and Environmental, Inc. dba Professional Duct Cleaning Co. has been committed from the onset of the COVID 19 virus to following a far stricter protocol than has been recommended by the various governmental agencies for sanitation and disease prevention measures. YOUR SAFETY IS OUR PRIMARY CONCERN. In order to help ensure the safety of our Clients and employees during the COVID 19 pandemic, this order was instituted by us company-wide and has been kept in place during the COVID 19 pandemic:


To: All Staff & All Technicians
Dated: 26 March 2020, Revised 28 March 2020

Due to the worldwide current situation with the COVID 19 virus, the following safety precautions are to be put in place and applied at all times to reduce the risk of spreading the disease to fellow employees and to our Clients.

The following actions are required of all employees of Optimum Indoor Air and Environmental, Inc. dba Professional Duct Cleaning Co. and shall be applied at all times:

  1. Get adequate sleep, eat well (nutritious foods), take proper supplements and get some exercise on a daily basis and avoid anyone who is ill.

  2. Your temperature is to be taken daily. If it is high you are to go or stay home, call a doctor and self-isolate. Your temperature will be taken immediately upon arrival at a work site or when coming into the office. If you have a temperature you will need to follow the preceding steps. You may not stay at work or be in the office.

  3. Keep your distance (try to maintain 6 feet) from your coworkers and Clients.

  4. Wash your hands often during the day with soap and hot water. Use hand sanitizer regularly.

  5. On a Client's job site, you are to wear clean disposable coveralls, face masks and gloves at all times. Protective shoe coverings should be worn in private homes always and in commercial environments when warranted.

  6. Clean and sanitize your work surfaces and tools often during the day. Sanitize them with a disinfectant such as hydrogen peroxide or alcohol-based products of no more than 70% alcohol. Bleach and water can also be used, 4 teaspoons bleach to 1 quart of water. NOTE: DO NOT MIX BLEACH WITH ANY OTHER CLEANING SOLUTION OR LIQUID EXCEPT WATER.

  7. Do not have physical contact with people, maintain your distance with your friends, coworkers and Clients.

  8. Wear proper work shoes, jeans or slacks without rips and long-sleeved shirts.

  9. Keep appropriate disinfectants and toweling on hand and daily sanitize your vehicle, your office work space, your tools and any materials you will be taking into a Client's space as well as your own person.

  10. Care for your Clients and your fellow employee's health by following these steps and let them see you have their interests at heart.

This is a real threat, especially to older members of our society. Care for yourself and for those around you.

Corky Landers

Tel: 323-340-8291

Of course we are licensed and bonded contractors, California License #984738. We carry general liability and workers' compensation insurance.

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