What about the use of gas phase ozone as a treatment for the inactivation of the COVID-19 virus?

Recent articles, webinars, and even quoted scientific studies have referred to the application of gas phase ozone from readily available ozone generators that can be used to inactivate the COVID-19 virus. Typically, in the past, these gas phase ozone generators have been widely used to combat smoke odors and other odors by restoration contractors after a fire, or in the use of treating the water as a biocide in hot tubs and whirlpools.

In an article entitled, “Ozone vs. Coronavirus: Ozone’s Efficacy as a Virucidal Disinfectant, “ published in the April 2020 issue of Restoration and Remediation Magazine, David Hart, inventor and manufacturer of several innovative systems in the cleaning and restoration industry for duct cleaning, and a manufacturer of an ozone generator made specific references to studies that certainly support the idea of gas phase ozone being used to inactivate viruses. In his article Mr. Hart recognizes, Dr. Gérard Sunnen, a medical doctor in New York City. Dr. Sunnen specializes in the uses of ozone in the medical field, ranging from cutting-edge ozone therapy to the use of ozone as a disinfectant.  According to Dr. Sunnen. “Ozone has unique disinfectant properties. As a gas, it has a penetration capacity that liquids do not possess. In view of the fact that , SARS-CoV-2, MERS, and previous SARS strains persist on fomites (surfaces) for up to several days, it is suggested that ozone technology be applied to the decontamination of medical and other environments”.

Mr. Hart further asked Dr. Sunnen to explain how gas phase ozone would work to inactivate viruses:  “Typically, viruses are small, independent particles, built of crystals and macromolecules. Unlike bacteria, they multiply only within the host cell. Ozone destroys viruses by diffusing through the protein coat into the nucleic acid core, resulting in damage of the viral RNA. At higher concentrations, ozone destroys the capsid or exterior protein shell by oxidation” explains Dr. Sunnen.  Further, “most research efforts on ozone’s virucidal effects have centered upon ozone’s propensity to break apart lipid molecules at sites of multiple bond configuration. Indeed, once the lipid envelope of the virus is fragmented, its DNA or RNA core cannot survive”.

Mr.  Hart finishes the article with his own conclusions: Ozone, having been proven in the lab and in the field to be an extremely effective virucide and full-spectrum antimicrobial, killing pathogenic bacteria and fungi, offers many benefits over alternative ways of disinfecting.” Mr. Hart believes that Ozone has a very important advantage over liquid disinfectants and antimicrobials because it has better penetration capabilities

Source: https://www.randrmagonline.com/articles/88901-ozones-efficacy-in-deactivating-coronavirus-like-pathogens

Dr. Sunnen and Mr.  Hart are by no means alone in their belief and understanding that gas phase ozone can be effectively used to inactivate the COVID-19 virus. There are several studies listed in the bibliography sections of other studies which reinforce this principle. The chief criticism of most of these studies is that they were sponsored, often paid for, and published by manufacturers of ozone generators themselves. The studies were not often independently scientifically peer reviewed.

But as you read the comments below from other scientists, be careful not to jump on the negative band wagon too easily and quickly when it comes to the application of ozone for this use. As you will see many of these experts quoted recognize the need for and call for more confirming or non-confirming research. Another criticism of the pro-ozone group that I have heard is that there has been no testing of the effectiveness of ozone at inactivating the specific COVID-19 virus. That criticism is true. But it is also true of all the disinfecting agents on the EPA Registered “N” list that is so often referred to. As of April 2020, none of these products were tested specifically against the COVID-19 virus. I f that is true, why does the EPA recognize these disinfectants as being effective and promote their usage? Well simply stated, previous studies submitted for these disinfectants have demonstrated successful inactivation of other coronaviruses. Because these disinfectants proved effectiveness against other strains of the coronavirus, the EPA is confident that they are effective against COVID-19. We may be well into the year 2021 before the specific testing against COVID-19 is completed for many of the registered disinfectants on the EPA N List.

Now let us look at the flip side of the argument as it relates to the potential use of gas phase ozone to inactivate the COVID-19 virus.

Steven M. Spivak, PhD is a Professor Emeritus, University of Maryland, Technical Advisor to RIA and an icon in the cleaning and disaster restoration industry. Recently in an email communication coordinated by John Downey at the Cleaning Industry Research Institute (CIRI), Dr. Spivak was asked about his opinion on the use of gas phase ozone as a potential bio-cide and specifically in the use against the COVID-19 virus.” ‘In years past I’ve seen and heard claims from aerial ozone generator machine supplier(s) that aerial ozone – If and when concentrated into close quarters, at “high concentration within unoccupied spaces,” might act as a germicide or disinfectant of sorts? But I’d never seen any scientific data or independent research to validate this – and whether or not the suspect use of aerial ozone efficacy and any -cidal benefits apply to bacteria; or mold & fungi; or viruses – or whichever?  It remains to be known and reliably tested, in my opinion and base of understanding.  I believe we are presently valid questioning about unknowns – unless proven otherwise – for efficacy of concentrated aerial ozone in unoccupied spaces? That is, how to use aerial ozone to affect a diminution or elimination of infectious COVID-19 or SARS-2 COVID, et al and especially in senior loving or elder care facilities? It remains to be tested and proven, albeit a viable research effort to discover”

In the same email communication, Dr. Stefan Wagener, SM (NRCM). CBSP, RBP. A scientific advisor for the Global Bio-Risk Advisory Council (GBAC) and Executive Director at Biorisk International stated: “In my opinion, the technology is not yet ready to be used in mainstream surface and room disinfection for COVID-19. Concentrations required are above health limits and cannot be used in occupied spaces. Monitoring of ozone levels might be needed as well as post-treatment processes (e.g., removal of ozone). It definitely requires further work and investigation.”

Also in the same CIRI email communication asking about the use of gas phase ozone for inactivating the virus, Dr. Eugene Cole took an even stronger stand: “It is hard to believe that anyone is even considering the use of gas-phase ozone as an indoor biocide these days.” Dr. Cole is Director of Research for LRC Indoor Testing & Research, Cary, NC; and formerly Professor of Environmental Health Sciences at Brigham Young University, Provo, UT. Dr. Cole referenced a research paper he released in 2003. From the the abstract of the study, “this review of the peer-reviewed, published, scientific literature has found no appreciable antimicrobial effect of gas-phase ozone on either airborne or surface microorganisms. Its potential role in the control of biological pollution in the indoor environment is not substantiated by scientific investigations”

In the summary of the study, Dr. Cole reinforces that the review did back what was stated in the abstract. The conclusion states: “In general, considering the extent of the variability of types and concentrations of biological pollutants, their spectrum of intrinsic inactivation resistances, their range of recognized reservoirs. And the extreme variability in environmental conditions relative to temperature, RH, air flow, and organic matter interference among others, there remains no recognized antimicrobial effectiveness nor recommended protocol for the use of gas-phase ozone for the indoor environment”

Source: “Gas-phase ozone: Assessment of Biocidal Properties for the Indoor Environment – A Critical Review,” Applied Bio-Safety, Volume 8(3), pages 112-117, Copyright ABSA 2003

So, what does the United States Environmental Protection Agency have to say on the subject? After all, if they are the organization that regulates claims of disinfection by liquid chemicals, what about gas-phase treatments? Well the first thing that the EPA says is that they do not test nor regulate, nor even have authority over the claims of disinfection by electronic devices and gas-phase treatments. This information is taken directly from their website:

Why aren’t ozone generators, UV lights or air purifiers on List N? Can I use them to kill the COVID-19? –   

These are examples of pesticidal devices. A pesticidal device is an instrument or other machine that is used to destroy, repel, trap, or mitigate any pests, including bacteria and viruses.

Unlike chemical pesticides, EPA does not routinely review the safety or efficacy of pesticidal devices, and therefore cannot confirm whether, or under what circumstances, such products might be effective against the spread of COVID-19. Accordingly, List N only includes surface disinfectants registered by EPA and does not include devices.

Pesticidal devices, while not required to be registered with EPA, are subject to certain regulatory requirements under FIFRA, including labeling and reporting requirements. Importantly, FIFRA prohibits the sale or distribution of misbranded pesticidal devices, i.e., pesticidal devices with false or misleading claims on their labeling. Selling pesticide devices with false or misleading claims about its safety or efficacy may subject the seller to penalties under FIFRA.

EPA only recommends use of the surface disinfectants identified on List N against SARS-CoV-2.”


The last sentence is the one I would ask professional cleaners, restorers, and facility managers to carefully consider. If you are going to use gas-phase ozone as a potential treatment step in dealing with the COVID-19 virus, you need to fully understand that the EPA does NOT consider it be a measure they would recommend. The EPA goes further in discussing Ozone on their website:

“Will an Ozone Generator protect me and my family from COVID-19?

No, do not use ozone generators in occupied spaces. When used at concentrations that do not exceed public health standards, ozone applied to indoor air does not effectively remove viruses, bacteria, mold, or other biological pollutants. Visit the Centers for Disease Control and Prevention’s website for best practices to protect yourself and your family.


Now keep in mind, this statement by the EPA is referring to running an ozone machine in an occupied environment. Mr. Hart and others who advocate for the use of ozone always recommend ONLY using in an unoccupied environment and take into consideration several other safety factors – removing all people, pets, and plants from the premises is just a start. This allows them to use gas phase ozone at much higher levels of concentration.

The deeper that I have gotten into my studies of the science of virus inactivation, and in learning more about how the research scientists, medical and research doctors, and other bio-risk assessment experts address the subject of COVID-19, one thing stands out to me: We don’t know much of anything for sure. We are still learning. As you hear politicians, the media, and others repeat the saying over and over again – “we are following the science” – they repeatedly act like the science is absolute, and that what the science says is a foregone conclusion. As I spend more time with the true scientists and research doctors, I find them taking on a much humbler attitude. It is almost “this is what we think we know based on our review of the facts we have in hand at the moment.” They are far more open to the fact they could be wrong, or something could change their mind than it seems many of the rest of us are. My interpretation is that they often take the best information that they have, and in what I would call a “leap of faith” (not sure they would appreciate that term) they reach recommendations for specific procedures based upon the best information, albeit science, they have at the time.

As the EPA stated in one of their answers to questions: Because air disinfection or purification devices do not need to be registered with the EPA, companies that make them aren’t required to disclose their efficacy data or verify their efficacy claims in their marketing materials. EPA does not routinely review the safety or efficacy of pesticidal devices, and therefore cannot confirm whether, or under what circumstances, such products might be effective against the spread of COVID-19If you are interested in gaining a fuller understanding of what this really means, and how it may apply to any and all other types of devices designed to treat or clean the air in a building, I highly recommend you take a look at the information on the website provided by Scientific Air Management, a manufacturer of an electronic air disinfection and purification device. If you visit https://scientificairmanagement.com/evidence/ you will find this company openly and readily ‘confesses” that the EPA has not reviewed their device. They then proceed to demonstrate how they did laboratory testing that did follow the recommended protocol the EPA uses to test efficacy of liquid disinfectants. From their website, “Even though air cleaning devices do not have to be registered, the EPA does have guidelines for the appropriate type and size of bioaerosol chamber in which to test. Scientific Air Management products are tested under these strict EPA guidelines and have laboratory-verifiable pathogen-killing efficacy. Two independent, nationally recognized lab facilities (Environmental Diagnostics Laboratory and MicroChem Laboratory), using EPA guideline conditions, performed efficacy testing in airborne pathogen killing rates. The following are the tests results and compiled reports. Per EPA guidelines, Scientific Air Management adhered to the following test protocols: 1); Test methods employed; 2) Contact time (minutes vs. hours); 3) Type of pathogen; and 4) Killing percentage (minimum 99.9995%).” The transparency of this company to the facts at hand is refreshing and leads me to believe that the claims they make about their device have a better scientific footing. Of course, these devices cost thousands more that a high-quality ozone generator and are really designed for on-going use in hospitals and other medical facilities. Still, the technology would apply to the treatment of the inactivation of COVID-19.

So where does using gas-phase ozone fit in to all of this? Perhaps the most important contribution, even considering the CIRI scientists, and the EPA’s concerns about effectiveness lies in the visual reinforcement. Generating a higher concentration of ozone into an unoccupied environment as an ADDITIONAL step beyond deep cleaning, and even beyond applying disinfectants to all common “touch points” may provide a higher level of “peace of mind” and confidence of the people who are going to live/work/shop in the home or building being treated. The problem lies when contractors take a little information and apply it indiscriminately. One strong example stands out where an “advisor” was advocating for the continuous running of an ozone generator in a COVID-19 stricken nursing home for the purpose of “killing the virus.” Not only would ozone have had no effectiveness at this level, it would have presented to occupants of the nursing home with another severe potential contributor to respiratory stress.

In conclusion, what can we do as contractors and facility managers with ozone? First, if we are going to use it we only do it in unoccupied environments. Well what exactly does that mean. Does everyone in an apartment house have to leave their apartment if we are using ozone in one apartment? If we are using ozone in one room of a 200,000 square foot commercial building, does the entire building have to be empty? Well, a well trained and certified cleaning or restoration contractor will take the right courses and learn how to use ozone in an environment safety and effectively. This includes the removal of all people, pets, and plants from the premises, as well as the removal or protection of vulnerable furnishings and electronics which may be comprised of a high level of natural rubber. High concentrations of ozone gas can break down natural rubber components.

With some level of assurance, properly used and applied, the application of ozone to treat an unoccupied environment hey could not likely not hurt and even might be helpful, so long as:

  • You must deep clean the entire indoor environment first (understand how the virus is transferred)
  • You apply an EPA registered disinfectant to all common touch points
  • You use the ozone machine strictly according to manufacturer directions in ONLY in accordance with generally accepted industry standards of care
  • Take precautions to protect people, pets, plants, and vulnerable furnishings
  • You do not oversell your capabilities and over promise what you can accomplish

In the interest of full disclosure, you should be aware that the company that the author of this article (R. Doyle Bloss) works for (HydraMaster) until recently manufactured an ozone generating device for use in fire and smoke damage restoration and odor control



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