Can Restoration Contractors Use HVAC Systems to Help Deal With the COVID-19 Pandemic?

Michael Pinto, Dave Heydinger, and Jacob Kooistra
on Wed, 11/11/2020
office building

The threat of SARS-CoV-2 (COVID-19) has brought increased attention to the role that the heating ventilation and air conditioning systems (HVAC) can have in dealing with microbiological contaminates. Recent events have added an urgency to the search for easy solutions to make buildings healthy. Cleaning and restoration professionals are on the front lines helping building owners by conducting detailed cleaning and offering to apply disinfectants safely and reasonably. During the delivery of these services, the discussions often turn toward additional steps that can be taken to protect building occupants.

The American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) offered general guidance in a paper published at the start of the pandemic that anticipated the subsequent confirmation of the airborne transmission of the virus.1 

Since the very beginning of the pandemic, numerous manufacturers have been heavily promoting their technology and products as enhancements to HVAC systems that reduce or eliminate viral particles. The confusing nature of the marketing claims led to the collaborative development of a white paper by Wonder Makers Environmental and Mathias Environmental, which reviews of a large number of these product claims. 

Supporting research was conducted to classify the types of technologies being promoted for use in HVAC units, provide a simple explanation of their method of operation, and summarize the benefits and concerns for each type of technology. The goal of the white paper was to summarize practical information that restoration professionals could use to potentially improve the indoor air in their own facilities, and answer questions that their clients often ask about pandemic concerns.

While the entire white paper has useful information about six specific technologies, this article focuses on two products designed to be installed as part of the ventilation system for a building: ultraviolet germicidal irradiation (UVGI) and polar/bipolar ionization. This focus is a result of the "push" that manufacturers of these types of systems have made to parts of the restoration industry over the past half decade that offer infection control services. 

Ultraviolet Light

Ultraviolet light (UV) is a form of electromagnetic radiation. It cannot be seen with the human eye because the wavelength is shorter than that of visible light. UV radiation is present in sunlight and can also be produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. The UV spectrum of light actually causes quite a bit of heating on surfaces, as compared to visible light. In addition to creating heat, UV light reacts with a number of chemical and biological molecules.

It is this ability of UV rays to damage living organisms that led to the understanding of which spectrums of light injure skin and eyes. This understanding of the harm the ultraviolet light could cause people and animals prompted the investigation of its effect on microorganisms. As an outgrowth of that line of inquiry, ultraviolet light has been in use as a disinfectant since the late 1800s,2 with a 1903 Nobel Prize awarded for work using UV light to control the spread of tuberculosis. Only more recently (with the advent of smaller, less maintenance-intensive, and survivable bulbs) has the technology become more useful as a broad-purpose, indoor air quality enhancement product. 

Using ultraviolet light to control infectious agents has been of such interest to the healthcare industry that this technology has developed into a specialty subsection of the use of ultraviolet light called “ultraviolet germicidal irradiation (UVGI).” Installation of ultraviolet lights in HVAC systems (and as stand-alone units in critical areas of medical facilities) has been proven to reduce infections.3 Extensive research has indicated that the effectiveness of such systems is based on multiple factors, including the specific wavelength of light utilized, the intensity of the light (which is what is determined by the strength of the bulb and the proximity of the contaminant to the source of the light), and the amount of time that the light interacts with the microbial contaminant. 

Therefore, it is important to note that the ASHRAE recommendation to add UVGI devices in high-density spaces such as waiting rooms, prisons, and shelters to address the COVID-19 pandemic takes those technical considerations into account. The ASHRAE document is direct in stating that UVGI equipment installed in air-handling units, inside ductwork, mounted as stand-alone units on the ceilings of rooms, and/or as portable equipment enclosed with an air distribution fan is based on the assumption that such systems will be designed and installed properly. A further assumption is that the equipment is being utilized to address airborne microorganisms, rather than installed to prevent biofilm buildup on cooling coils or drip pans.

Properly Evaluating the Appropriateness of UVGI Technology

ASHRAE's approach is supported by the Food and Drug Administration (FDA) in their recent guidance document related to ultraviolet lights as part of a response to the pandemic.4 However, the FDA notes that UVC lamps used for disinfection purposes may pose potential health and safety risks, depending on the UVC wavelength, dose, and duration of radiation exposure. The risk increases if the unit is not installed properly or used by untrained individuals. Some of the specific concerns listed include: damage to skin and eyes for individuals exposed to UV light, production of ozone as a byproduct of the operation of the system, degradation of materials subjected to exposure to UV light, and potential exposure to mercury if the UV bulb is broken. The FDA document further notes that the virus will not be inactivated if it is covered by dust or soil, embedded in porous surfaces, or on the underside of a surface. The FDA also encourages the use of UVGI systems that employ bulbs that operate at a very specific, safer wavelength.5

Overall, the evidence makes it clear that the use of ultraviolet light systems inside existing HVAC units (or as stand-alone, shielded units mounted toward the ceiling in occupied spaces) can make a positive difference in controlling the spread of infectious aerosols. Even so, in order to provide a measurable positive impact, the UV light system has to be sized and installed properly in conjunction with HVAC systems. That way, contaminants passing through the area of the ductwork illuminated by the lamp(s) receive the proper dose and duration of UV radiation to inactivate viral particles. Because of these variables, marketing claims indicating that a small UV bulb added to HVAC ductwork will be effective in minimizing the transmission of the virus responsible for COVID-19 should be met with significant skepticism. 

Polar-Bipolar Cold Plasma Air Ionization

An ionizer is an electronic device that imparts an electrical charge to particles that pass near the ionizer. These types of devices use electrically-charged fields to interact with the air passing by it to create an electric charge, or “ionize” any aerosol contaminants. This includes small molecules of material, as well as larger particles of dust and debris. 

Ionization systems have a variety of different names depending on the specific type of electric charge they impart to aerosol contaminants and the way that the charge is created. Polar ionization systems adjust the existing electrical condition, leaving the impacted aerosols with only one type of charge: positive (+) or negative (-). Bipolar systems also impart an electrical charge to the aerosol contaminants, but those systems create both (+) and (-) charged ions. To further complicate matters, cold plasma is the term used for equipment that produces positive and negative ions (i.e., a bipolar ionizer) in a way that the electrical charge impacts the gaseous parts of the air, as well as the aerosol contaminants.

The overall benefit of ionizing aerosol contaminants (and even the gases of the air that they float in) is that the charged aerosols are attracted to one another, forming larger particles, which either drop out of the air or are easier to capture. An additional benefit is that many microorganisms are damaged when they are exposed to electrical charges after coming in contact with an ionized aerosol. There is also a proven impact that ionized aerosols have on volatile organic compounds (VOCs). VOCs are typically made up of long chains of atoms, which are broken apart upon contact with the ionized aerosols. The broken parts of the VOCs are called “reaction byproducts.” If the concentration of ionized particles is great enough, then the reaction byproducts are further broken down, until they reach a state of stable, basic elements, like water or CO₂. However, until that process reaches an end-stage, both the existing VOCs in the building and the fragments of the original molecules (created by contact with the ionized particles) can cause ill health effects.

Concerns With Air Ionization Systems

The advantages of ionization systems (as aids to the HVAC equipment) revolve around their ease of installation at a relatively low cost. Despite those benefits, there are concerns over the efficacy and application of HVAC ionization systems because of the difficulty in proving their effective reach. Currently, relatively inexpensive meters make it possible to measure ionized particle concentration in the ambient air. Such measurements in real-life applications need to be evaluated carefully, as there are many sources of ionized particles in most buildings, including ambient radon levels, cooking, evaporating water, computers, copiers, certain light fixtures, and even faulty wiring. With this in mind, measuring the true impact of an HVAC system ionizer can be difficult to do with precision. 

The science of the potential benefits of ionized aerosols is clear from decades of laboratory studies. Translating those benefits into workable systems (in dynamically occupied buildings with a wide variety of HVAC components) is challenging, as the positive impact of ionizers is dependent upon the type of electrical charge and volume of ionized aerosols that are produced. While most of the advertisements for such systems tout the health benefits of being exposed to an increased level of ions (especially negative ions), there are limited medical studies validating the claims. 

One recent medical study looked at the overall health impacts of using ionizers that impart a negative charge on the aerosols and concluded that:

“….. negative ions, possibly along with their reaction products with the room air constituents, adversely affect health. The downsides do not support the use of negative ion air purifiers (NIAPs) as a health‐based mitigation strategy to reduce PM2.5 (small particulate) exposure…”6

Even though that study (completed in August 2020) focused on ionizers as HVAC aids to control airborne particulates, those potential adverse health effects need to be balanced against the improvement of the air quality that such systems may offer, in regards to a reduction of viral contaminants.

Knowing these basics of UVGI and ionization systems allows restoration professionals to take an active part in the discussions about technology that can supplement the basics of cleaning and chemical application. However, in such conversations, regardless of what type of technology being considered, the recommendation of supplemental equipment should never be made simply to calm the fears of owners or occupants. As one safety and health expert (who specializes in infection control) warned when explaining how HVAC systems could be helpful in addressing COVID-19:

“It is critical to remember that each indoor environment is unique; conditions within each indoor environment are dynamic, and there is not a one-size-fits-all strategy for infection control.”7

More details on these types of technology and additional information on other systems can be found in the full paper. For a copy, please contact Michael Pinto or Jacob Kooistra at or by phone at 269-382-4154. 


End Notes:

1. ASHRAE Position Document:   

2. A summarized history of ultraviolet light for disinfection: 

3. Aerosol Susceptibility of Influenza Virus to UV-C Light: 

4. The Food and Drug Administration (FDA) provides an objective summary of ultraviolet light as a means of dealing with the COVID-19 pandemic: 

5. Report about a safer UV light for COVID-19: 

6. Medical study about the health effects of negative ion air purifiers: 

7. Summary article on managing indoor air quality on the COVID-19: 


About the Authors

Michael Pinto and Jacob Kooistra are with Wonder Makers Environmental. Wonder Makers specializes in the identification and control of asbestos, lead, IAQ, mold, industrial hygiene, and chemical problems. The Wonder Makers team evaluates site conditions, conducts risk assessments, and develops recommendations and/or specific work plans to control hazards and protect the building owners, occupants, and restoration crews. Their laboratory also analyzes mold samples and provides certification training about multiple indoor contaminants, including infectious agents. Pinto and Kooistra can be reached at or by phone at 269-382-4154. 

Dave Heydinger is with Mathias Environmental, an organization that evaluates, designs, and implements indoor air quality strategies to battle the spread of pathogens in commercial and public facilities. These include the SARS-CoV-2 novel coronavirus and the H1N1 Flu virus. Dave can be reached at or by calling 706-705-6322.