Ozone Approvals Summary


Approvals, Recommendations and Guidelines:



  • More than 100 years of ozone use worldwide
  • United States Food and Drug Administration approved for bottled water in 1982
  • EPA allows use of ozone with no reporting or record-keeping
  • FDA Expert Panel approved as GRAS (generally recognized as safe) in 1997
  • FDA granted petition for use with fruits, vegetables, meat, poultry, in June 2001
  • Approved under USDA Organic Rule in 2000 Regulatory Details:

EPA Requirements for Ozone Under the FIFRA


When the FIFRA was enacted years ago, EPA was required to regulate any chemical for which a pesticidal claim is made. An example of a claim made by purveyors of ozone equipment that can be considered to be a pesticidal claim is “ozone kills/inactivates microorganisms (SARS-CoV-2/Covid-19), fungi, molds, algae, etc.). Pesticides historically are chemicals of commerce that are supplied in bulk in cylinders or containers that are shipped throughout a geographic region. Ozone does not fall into that category of “chemicals”, in that it is generated and used on-site, is not transported or stored, and quickly dissipates or is self-destroyed during use.

Consequently, in interpreting the requirement of the FIFRA, EPA concluded that ozone is not a “pesticide chemical”, and therefore the gas itself is not to be regulated under the FIFRA. However, ozone generators, while not chemicals, are regulated under the FIFRA as “pesticide devices”, as is equipment that produces ultraviolet radiation.

Under the FIFRA, EPA requires that all pesticide devices (which includes ozone generators) that are made or distributed in the USA, for which a pesticidal claim is made must carry an Establishment Number. This is a number granted by the EPA upon receipt of a properly completed EPA Form 3540-8 (rev. 5/99), “APPLICATION: ESTABLISHMENT REGISTRATION FOR PESTICIDE

AND DEVICE PRODUCERS”. Once an Establishment Number has been assigned to a manufacturing facility,

that number is required to be placed on devices (ozone generators) produced at that facility.

The establishment number confirms that the facility that manufactures ozone generating devices has complied with the registration requirements of the FIFRA.

Purfresh EPA Pesticide Device Establishment Number: 66769-CA-2

CDC Infection Control Sterilization Methods


Ozone has been used for years as a drinking water disinfectant. Ozone is produced when O2 is energized and split into two monatomic (O1) molecules. The monatomic oxygen molecules then collide with O2 molecules to form ozone, which is O3. Thus, ozone consists of O2 with a loosely bonded third oxygen atom that is readily available to attach to, and oxidize, other molecules. This additional oxygen atom makes ozone a powerful oxidant that destroys microorganisms but is highly unstable (i.e., half-life of 22 minutes at room temperature).

A new sterilization process, which uses ozone as the sterilant, was cleared by FDA in August 2003 for processing reusable medical devices. The sterilizer creates its own sterilant internally from USP grade oxygen, steam-quality water and electricity; the sterilant is converted back to oxygen and water vapor at the end of the cycle by a passing through a catalyst before being exhausted into the room. The duration of the sterilization cycle is about 4 h and 15 m, and it occurs at 30-35°C. Microbial efficacy has been demonstrated by achieving a SAL of 10-6 with a variety of microorganisms to include the most resistant microorganism, Geobacillus stearothermophilus.

USDA final rule on ozone dated 12/17/2002, FSIS Directive 7120.1

Safe and suitable ingredients used in the production of meat and poultry.

FSIS Directive 7120.1 States: Ozone for use on all meat and poultry products. Ozone can be used in accordance with current industry standards of good manufacturing practice. No other guidelines are given on levels or dosages of ozone. Reference 21 CFR 173.368

USDA CFR 173.368

Ozone (CAS Reg. No. 10028-15-6) may be safely used in the treatment, storage, and processing of foods, including meat and poultry (unless such use is precluded by standards of identity in 9 CFR part 319), in accordance with the following prescribed conditions: (a) The additive is an unstable, colorless gas with a pungent, characteristic odor, which occurs freely in nature. It is produced commercially by passing electrical discharges or ionizing radiation through air or oxygen. (b) The additive is used as an antimicrobial agent as defined in CFR 170.3(o)(2) of this chapter. (c) The additive meets the specifications for ozone in the Food Chemicals Codex, 4th ed. (1996), p. 277, which is incorporated by reference. The Director of the Office of the Federal Register approves this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies are available from the National Academy Press, 2101 Constitution Ave. NW., Washington, DC 20055, or may be examined at the Office of Premarket Approval (HFS-200), Center for Food Safety and Applied Nutrition, Food and Drug Administration, 200 C St. SW., Washington, DC, and the Office of the Federal Register, 800 North Capitol St. NW., suite 700, Washington, DC. (d) The additive is used in contact with food, including meat and poultry (unless such use is precluded by standards of identity in 9 CFR part 319 or 9 CFR part 381, subpart P), in the gaseous or aqueous phase in accordance with current industry standards of good manufacturing practice. (e) When used on raw agricultural commodities, the use is consistent with section 201(q)(1)(B)(i) of the Federal Food, Drug, and Cosmetic Act (the act) and not applied for use under section 201(q)(1)(B)(i)(I), (q)(1)(B)(i)(II), or (q)(1)(B)(i)(III) of the act.

USDA Guidance on Ingredients and sources of radiation used to reduce microorganisms on carcasses, ground beef, and beef trimmings:

Ozone is classified a Secondary direct food additive/processing aid allowable for all meat and poultry products.

FDA Federal Register Vol. 66 No.123 June 26, 2001

The Food and Drug Administration (FDA) is amending the food additive regulations to provide for the safe use of ozone in gaseous and aqueous phases as an antimicrobial agent on food, including meat and poultry. This action is in response to a petition filed by the Electric Power Research Institute, Agriculture and Food Technology Alliance.

OSHA Ozone Regulations

OSHA guidelines for O3 in the workplace are based on time-weighted averages. Ozone levels should never exceed the following average: 0.10 ppm (parts per million) for 8 hours per day exposure. For more detailed information on safe ozone levels, see the bullet points below.

The OSHA website cites several ACGIH (American Conference of Governmental Industrial Hygienists) guidelines for ozone in the workplace:

0.2 ppm for no more than 2 hours exposure

0.1 ppm for 8 hours per day exposure doing light work

0.08 ppm for 8 hours per day exposure doing moderate work

0.05 ppm for 8 hours per day exposure doing heavy work

More information: http://www.osha.gov/dts/chemicalsampling/data/CH_259300.html

OZONE Effective & Safe When Rules Followed


Ozone is an extremely effective oxidative disinfectant and has been used in the medical, pharmaceutical, food processing, and water treatment industries for decades.

The reason ozone is used is simple. It can be cheaply and efficiently created on-site, and the disarming effect of ozone on microorganisms is well understood and has been proven as an effective tool for mitigating many different unwanted compounds and microorganisms.

Why does the EPA warn against ozone generators on the market?

Although ozone is an effective tool, it is only effective when used SAFELY.
As an example, bleach is a very effective tool when used for its intended purpose. Bleach is ineffective as a hand soap because it is not designed for human consumption or skin contact.

Companies that produce general-purpose bleach have very clear instructions and recommended safety equipment that should be used when using bleach for the safety of the user.

When using ozone, the same precautions need to be taken, but they are often not clearly stated by the manufacturer of the ozone generator and there are no controls in place on cheaper machines that ensure users are operating the generator effectively or even safely. Therefore, the EPA warns against using these commonly available cheap ozone generators in residential areas.

The Purfresh Difference – Safety First

Ozone is a great tool that can be used to protect people from unwanted and potentially dangerous substances that can be found in residential and commercial spaces. To keep people healthy and safe from these particles and microorganisms, ozone must be used when the space is completely unoccupied, and the ozone must be sensor-level controlled (most cheap ozone generators do not offer sensor-level control). These are the most important safety measures that must be taken in order to use ozone appropriately and effectively.

Purfresh Clean Systems utilize fully automated, remotely controlled devices that have built-in safety features that ensure the space is unoccupied and safe to reenter when the space has been cleaned. These include:

  • Safety placards posted on all entrances and exits to the space being treated.
  • Ozone sensors – Both for controlling the ozone level and for making sure the space is clear of any ozone when the space needs to be accessed again.
  • Warning and control lights
  • Remote control capabilities – This important feature allows operators to turn on and off the equipment from outside the space that is to be cleaned. This isn’t offered by cheap ozone equipment suppliers.
  • Activated Carbon and HEPA filters – These turn on after the ozone treatment to reduce possible excess VOCs, formaldehyde, and small particles and reduce the ozone degradation time.

Ozone and Smog – Incorrect Interpretations

Ozone and smog pollution are often considered together when the topic of ozone use is discussed. These are separate issues, and the industrial production of ozone is NOT a component of smog. Dangerous levels of particulate material, CO2, and other smog-pollution components cause harm to humans. Extremely low levels of atmospheric ozone measured when smog is present are not dangerous to humans.

When ozone is produced naturally without the presence of other harmful contaminants like VOCs and NO2, the ozone breaks back down naturally into oxygen. This is a normal result of the instability of ozone and the short half-life inherent in the ozone molecule.

The important consideration is that ozone is not the cause of the low air quality, but the result. Excess NO2 and VOCs in the air from pollution cause this unhealthy ozone cycle to begin. Therefore, the EPA has instituted ground-level ozone standards. These standards are important, as lowering pollution in our air will improve the unhealthy ozone cycle and improve overall air quality for all people.

Purfresh SPACE equipment is proven to follow and adhere to all ozone application use rules and guidelines issued by the FDA, USDA, EPA, OSHA, and CARB.

Purfresh Clean ozone sanitizing technology now in use at Texas A&M at Galveston

Purfresh Clean CEO Christian DeBlasio has donated $75,000 of air treatment units and services to his alma mater, Texas A&M University at Galveston in Galveston, Texas, to prevent the spread of SARS-CoV-2 and COVID-19. His concern for the welfare of the students and faculty inspired him to make the donation and do everything possible to keep them healthy while they are in school.

The machines apply Oxygen-3 (O3) molecules to sanitize sealed, unoccupied indoor spaces. O3 is a reactive gas composed of three atoms of oxygen. In low concentrations (at the parts per billion level), ozone is scientifically proven to destroy viruses as well as bacteria and odors by bonding with and breaking down their molecular structure. Ozone then degrades back to oxygen, leaving behind no residue. Because molecules are broken down rather than simply covered up, the room is truly clean after the unit’s cycle is complete. The machines’ output is dry air, so they will not damage any room furnishings. They are used overnight so they have enough time to ensure complete safety by the time people enter the rooms. Each unit can clean and sanitize a 2500 square foot room with 12-foot ceilings in 4-5 hours.

Because O3 is a gas, it has the advantage of being able to permeate the entire space, including air and any aerosol viruses, leaving no corner untouched. In a 2009 University of British Columbia study, ozone was proven to inactivate over 99% of enveloped viruses such as SARS CoV-2 (the virus that causes the coronavirus disease, COVID-19). O3 is approved by the FDA and USDA to disinfect food and water as well, and a 2020 Georgia Institute of Technology study, found that it may have additional applications to clean reusable PPE during shortages.

In 2020, Purfresh Clean’s units were used in U.S. Army National Guard training exercises. Four units are now being used in the Dining Hall on the Galveston Campus due to the high density in this location. The units are used nightly to aid in ensuring that students, faculty, and staff enter a clean environment each morning.


Launched in May 2020, Purfresh Clean has developed patented O3 technology solutions to help businesses, schools, and governments safely, quickly, and comprehensively eliminate 99.9% of SARS-CoV-2 from their indoor spaces and continue operations. In late 2020, United States Army National Guard training facilities started using Purfresh Clean to disinfect shared equipment and communal interior spaces. Purfresh Clean units are available globally and are FDA, EPA, and OSHA compliant. The company’s mission is to protect people and purify environments from viruses, bacteria, mold, and odors. Purfresh Clean is headquartered and manufactured in the U.S.

Learn more about Purfresh’s patented O3 technology.

Purfresh Clean equipment deployed for virus spread risk mitigation at U.S. Army National Guard training exercises

 PRLog — In response to the COVID-19 pandemic, Ravenswood Solutions recently deployed Purfresh CLEAN systems and equipment for virus spread risk mitigation at the U.S. Army National Guard’s (ARNG) eXportable Combat Training Capability (XCTC) training exercises. Ravenswood has supported XCTC exercises for 14 years but faced a unique challenge in 2020 as the pandemic surged.

“Purfresh decontamination technology with ozone helps to create the cleanest environment possible for all personnel involved in the XCTC program,” said Christian DeBlasio, CEO of Purfresh.

When applied to unoccupied interior spaces before and after group meetings or in containment units for shared personnel equipment, Purfresh CLEAN ozone systems remove viruses, bacteria, and odors from both air and surfaces. Ozone, also called O3, is made of pure oxygen, leaves zero residue, and is only applied to unoccupied spaces or special containment units.

“During our XCTC training rotations, Ravenswood’s top priority is supporting the safety of our troops,” said Dan Donoghue, President and CEO of Ravenswood Solutions. “This year, we found a great partner in Purfresh to help us achieve that goal in this unprecedented situation.”

By the end of the 2020 training year, Ravenswood will have safely trained more than 2,300 troops.

For more information on how Purfresh’s ozone system and current research on the technology, go to: Purfresh Clean.

View complete press release here.

Studies Prove Purfresh’s CLEAN Product Line Deactivates COVID-19 on Surfaces & in Air – Featured at Biocom

With COVID-19 reported to live on surfaces up to 72 hours and easily transmitted through the air in droplet form, it’s more important than ever to decontaminate interior spaces, lab equipment, and other daily-use items being shared by multiple individuals. For over a decade, Purfresh Clean has provided ozone-based services to companies around the world, delivering a scientifically proven way to quickly destroy germs and flu viruses, bacteria, mold, and odors from air and surfaces simultaneously. The company has several different products that can disinfect equipment, air, surfaces, and unoccupied, enclosed rooms or spaces.

It has also been proven that ozone at low concentrations in the parts per billion level can be used to deactivate viruses such as SARS-CoV-2 (COVID-19).

With a mission to provide people, companies, and organizations with a daily solution that mitigates the invisible risks of environmental contaminants, Purfresh Clean is assisting companies in their safe reopening efforts with products utilizing a natural biocide that attacks airborne pathogens and aerosol + surface respiratory droplets with 99% efficacy when properly applied.

Ozone is a scientifically proven organic molecule that has been used for decades to quickly destroy germs like cold and flu viruses, harmful bacteria, molds, and other pathogens. Purfresh Clean’s ozone generators can disinfect an enclosed area of potential viral contamination, both in the air and on affected surfaces. Anywhere that air can reach, ozone can reach, and will destroy viruses on contact. The ozone is distributed via fan-generated airflow into the application area and, depending on ozone concentration, can deactivate a virus in as little as 30 minutes. Ozone has the advantage over other disinfectants in that it is a gas, so that it can permeate all areas of a room and deactivate the hardest to reach areas. Ozone can also disinfect aerosols suspended in the air and decomposes to oxygen, so it is residue-free.

As with any solution mitigating the spread of viruses, proper application is paramount and ozone technology is no different. Although ozone is a natural biocide, it must be deployed on-site, in unoccupied rooms, and the amount of time it requires to overtake the virus in the air and on surfaces depends on various atmospheric conditions. In addition to being properly deployed, the ozone created to kill the virus must be destroyed. All Purfresh Clean units take care of this remotely through cloud-based intellipur software that allows for remote activation of units, atmospheric control, and monitoring, as well as record of cleaning and at what percentage efficacy.

Learn more information about Purfresh Clean’s decontamination services, which have an application pending for Emergency Use Authorization with the FDA.

View article at Biocom website.

Blue Oak Brewing company using Purfresh SPACE

Blue Oak Brewing in San Carlos California is using Purfresh SPACE to decontaminate their facility every night.

“Blue Oak Brewing has deployed top decontamination technology at our facility to provide the cleanest and safest environment possible for our customers and employees. We now use Purfresh Clean ozone systems to decontaminate the interior of our facility every day.  Ozone also called O3, is made of pure oxygen, and is one of the best know sanitation processes to remove viruses, bacteria, and odors from the air and from all surfaces.” Said owner Alex Porter.

To learn more about decontamination of closed spaces click the link.

Manufacturing photos of Purfresh SPACE

Below we want to share some photos of our Purfresh SPACE product during manufacture.

Purfresh SPACE is a decontamination service for closed spaces up to 15,000 sqft, including  company offices, doctors offices, homes, restaurants, bars or closed spaces up to 15,000 sqft.

To learn more about decontamination of closed spaces click the link.

How 3 American Technology Companies are Adapting to Help During the Coronavirus Crisis

The coronavirus pandemic is one of the biggest crisis inciters in recent humankind history. While it is true that medical technology has advanced enough to come up with solutions in real-time around the world, the truth is that 2020 has ended for us all as it will take at least 18 months to find a viable vaccine.

To date, there are over two million confirmed cases worldwide and a little over 140,000 deaths, a number which modifies by the hour. Needless to say, that the pandemic will bring a deep economic crisis.

In this challenging environment, we’ve seen the best and worst of humanity unfold in the past weeks. But these times call for positive statements so, in this article, we will talk about three American technology oriented companies that are sharing their expertise with the world to fight COVID 19.

1) Alphabet (Google)

A major challenge that comes with the pandemic is to know if you’ve been exposed to the virus to take proper action. Tech company, Alphabet, has partnered with Apple to turn smartphones into notification devices to tell people if they have been exposed.

Fake news is a secondary epidemic, the parent company of Google, is also making alliances to moderate content on the internet and boosting trustworthy sources of information.

A concrete effort made by Google was to stop all ads related to coronavirus as they couldn’t guarantee proper moderation. As the crisis moves forward, they have gradually allowed these ads.

Learn more. https://time.com/collection/finding-hope-coronavirus-pandemic/5820602/sundar-pichai-big-tech-coronavirus

2) Tesla

Another challenge for humankind is the lack of mechanical ventilators available at hospitals worldwide.

Mechanical ventilators help people breathe when they can’t do it on their own, which is something that happens when COVID 19 complicates. The world just wasn’t ready to intubate hundreds of thousands of people simultaneously.

This lack of medical equipment is considerable everywhere, from the richest to the poorest countries. Is because of this that Tesla, the electric energy company specialized in high-end electric cars tasked its engineers with designing and building ventilators out of car parts.

This massive effort to repurpose car parts seeks to alleviate the ventilator shortage in The United States. So far, Tesla has shipped over 1,000 ventilators to around 50 hospitals in the United States and abroad. This has prompted investors to pick Tesla over other motor companies such as GM or Toyota as they trust they will emerge stronger from this crisis.

Learn more:

3) Purfresh

The third company we’re going to talk about is Purfresh and its new division Purfresh Clean. Purfresh is a company that has the technology to sanitize food using ozone. Ozone sanitation is FDA and USDA approved to prevent decay and propagation of bacteria and viruses in fresh produce without using chemicals.

With new investments to acquire more equipment, Purfresh seeks to ensure the safety of food transported into The United States. The World Health Organization recommends a healthy diet to boost the immune system, and this diet consists of fruits and vegetables as part of a well-balanced diet.

This is why Purfresh technology plays such an important role in fresh produce distribution in The United States. The technology is used in international shipping containers to reduce decay and pathogen proliferation.

Purfesh Clean: More importantly through their new Purfresh Clean division, the company adapted their Ozone technology to support the healthcare and other essential industries during this Covid-19 crisis by offering sanitization solutions for the disinfection and decontamination of offices, medical facilities and equipment.

This is reached via Purfresh Office 3 ozone products:

  1. Purfresh SPACE, a decontamination service for company office, doctors office, home, or closed spaces up to 15,000 sqft
  2. Purfresh CUBE, a small enclosed box that you can use at a medical facility or doctor’s office to decontaminate small batches of small items, masks, gloves, goggles, or other small PPE equipment.
  3. Purfresh TITAN, a large 20 or 40 foot size ocean container that we deliver to your medical facility or office, and you can place large and small items in large quantities into the container for a 3-12 hour decontamination process.


Learn more: https://purfreshclean.com


It is time for humankind to unite and to get the best from this unexpected and difficult sanitary emergency, that we follow the lead of these companies and try to help those at our reach as much as we can.

To contact us please click here.

Purfresh Repurposes Its Ozone Technology to Support Hospitals Fighting the Coronavirus

(HAYWARD, CALIFORNIA, April 1, 2020) – As medical professionals at hospitals across the country fight to save victims of COVID-19, they struggling with limited supplies of personal protective equipment (PPE) and ensuring their facilities are free from the virus. Purfresh announced today that it is repurposing one of its products to support hospitals in providing doctors and nurses with the protection and safety they need.

“Doctors and nurses using masks and gloves on patient after patient threatens their safety and their ability to provide the care victims of this horrible pandemic need,” said Christian DeBlasio, President and CEO. “We can deploy our ozone systems quickly and efficiently to alleviate some of the PPE supply issues at our nation’s medical facilities, as well as ensure the safety of the facilities themselves.”

Normally used to reduce decay and pathogens, control ripening and enhance food safety for fruits and vegetables transported around the world, Prufresh’s ozone technology has been proven to reduce the risks associated with bacteria, pathogens and viruses like the Covid-19 coronavirus. It has been approved for use by the FDA, USDA, and EPA and the company has applied for FDA Emergency Use Authorization (EUA) for use with hospital equipment. The EUA helps strengthen the nation’s public health protections by giving the FDA Commissioner the authority to allow unapproved medical products, or unapproved uses of approved medical products, in an emergency to diagnose, treat, or prevent serious or life-threatening diseases or conditions.

How the Purfresh System Works
The Purfresh Clean product line includes small cube-shaped boxes and large mobile units, allowing medical facilities to place not only PPE items into the containers, but also other items, including furniture, ventilators, or other potentially contaminated items. Ozone is a scientifically proven organic molecule which has been used for decades to quickly destroy germs like cold and flu viruses, harmful bacteria, molds and other pathogens. Purfresh’s ozone generators can be used to disinfect an enclosed area of potential viral contamination, both in the air and on affected surfaces.

Anywhere that air can reach, ozone can reach, and will destroy viruses on contact. The ozone is distributed via fan-generated airflow into the application area and, depending on ozone concentration, can deactivate a virus in as little as 90 minutes. A unit mounts into an existing evaporator fan access panel and can be operational in as little as 30 minutes; containers can be delivered to medical facilities or hospitals in as little as 24 hours.

Ozone has the advantage over other disinfectants in that it is a gas, so that it can permeate all areas of a room, and deactivate the hardest to reach areas, including the ventilation system. Ozone can also disinfect aerosols suspended in the air and decomposes to oxygen, so it is residue free.

“This crisis has created a much more urgent application of our product and we can scale up quickly to support medical facilities around the world,” said DeBlasio. “Purfresh has the technology, we’re ready to deploy it and we want to help so that the heroes on the frontlines of this pandemic, our medical professionals, can stay safe and focus on what they need to do – save lives.”

  • To learn more about Purfresh Clean Products please click here.
  • To contact us please click here.



The inhibitory and lethal effects of ozone on pathogenic organisms including viruses have been observed since the latter part of the 19’th century. (Shentag, Akers, Ph.D., Campagna, & Chirayath)

Viruses are very small microscopic particles containing DNA or RNA, lacking the capacity to reproduce themselves outside of a host. Viruses are smaller than bacteria or fungi. They attach themselves to living cells injecting their genetic code into the host, taking over the host’s cellular machinery to reproduce themselves at a rapid rate.

Covid-19, otherwise known as SARS-CoV2 is an enveloped coronavirus, which means that the viral genetic material exists inside a lipid envelope within a protein capsule. The structure of Covid-19 is very similar to that of the Severe Acute Respiratory Syndrome (SARS-CoV1) virus, which is also an enveloped corona virus, sharing over 80% of the same genetic code. The Middle East Respiratory Syndrome (MERS-CoV) virus is also a coronavirus.

Table 1 shows the relative ease of disinfection (biocide susceptibility) for various pathogens, reproduced from The Handbook of Water and Wastewater Microbiology. (Microbial Response to Disinfectants, 2003)

In the United States, in order to make claims regarding the performance of a disinfectant such as ozone, the product must be listed by the EPA. The process allows for rapid approval in “Section V, Outbreak criteria associated with Emerging Pathogens”, diseases that appear in the human population for the first time. Application requires classification of the virus into large and small non-enveloped viruses, and enveloped viruses. Instructions state “Enveloped viruses are the least resistant to activation by disinfection”, and lists the viral families accepted in this category showing Coronaviridae, which includes COVID-19. These EPA instructions are consistent with claims by others regarding the ease of disinfecting coronaviruses. (EPA, 2016). We recently applied for registration as a disinfectant for COVID-19 based on the data in this report.

Breathing ozone gas can be hazardous to human health. The Occupational Safety and Health Administration (OSHA) has set Public Health Air Standards of 0.1 ppm for 8 hours or 0.3 ppm for 15 minutes as the limit of the amount of ozone to which people can be safely exposed. Air cleaners based on ozone should not generate ozone levels above the Public Health Standards, which are considered below any disinfectant activity. (Shentag, Akers, Ph.D., Campagna, & Chirayath)

Studies of Ozone use for Decontamination of Viruses

Zhang, et al, (Zhang, Ziao, Zhou, & Gao, 2004) demonstrated that SARS-CoV1 could be destroyed by 27 ppm of ozone in solution applied for four minutes. SARS-CoV1 is nearly identical in structure to COVID-19. Ozone solutions at concentrations of 18 ppm, and 5ppm were also effective.

Hudson, et.al. (Hudson, Sharma, & Vimalanathan, 2009) dried 12 different virus strains onto different surfaces that were placed into a test office for ozone treatment with low (38%) and high (70%) relative humidity. The selected viruses were known pathogens, including influenza, and mouse coronavirus, which are both enveloped viruses, like COVID-19. The ozone generator delivered up to 20 ppm for 20 minutes. Reduction in viral count depended strongly on relative humidity, with an average of 32% reduction at low humidity, and an average reduction of 99.8% at high humidity.

The Hudson study also evaluated the ability of ozone to mitigate viral aerosols. A liquid suspension of Influenza virus was sprayed into a laboratory chamber with and without 20 ppm ozone, and viable viral counts were measured in the condensate. On average, 99.73% of the virus were inactivated from the aerosol, indicating that ozone also deactivates aerosol born viruses.

In order for ozone to deactivate viruses in aerosols, ozone must be sufficiently solubilized in water, so that the ozone can reach the virus. Figure 1 shows the solubility of ozone at different gas-phase concentrations of ozone, and at various temperatures. (Ozone Solutions, n.d.)

On average these results show that the ozone concentration solubilized in water is 26% of the gas-phase concentration at 20 degrees Celsius, indicating that ozone can penetrate into aerosol droplets at meaningful concentrations. This figure also shows how the solubility of ozone in water increases with decreasing temperature.

Tseng and Li (Tseng & Chihshan, Volume 70. No. 19 (June 2008)) measured the survival curves of four different viruses on a Gelatin-based medium over a range of ozone concentrations (600 ppb, 900 ppb, and 1200 ppb) at 55 and 85% relative humidity, for a time period of up to 120 minutes. Table 2 shows selected results from the study.

The results show that the enveloped virus Phi-6 required the least amount of time for deactivation across all ranges of ozone concentration and relative humidity. For all viruses, increasing ozone concentration significantly reduced the time required for deactivation. Increasing relative humidity also had a significant impact on reducing the time to deactivate the viruses.

Roy & Wong (Roy & Wong, Mechanism of Enteroviral Inactivation by Ozone, 1981) studied how ozone treatment impacts the viability of poliovirus. Poliovirus is a non-enveloped virus that is transmitted into its host through the gut. Treating the system with 0.5 mg/liter (500 ppb, or 0.5 ppm) of ozone for ten seconds destroyed over 90% of the virus. This study also discovered that ozone damaged the protein coat of the virus, although this damage did not appear to impact the viability of the virus. Instead, the ozone directly attacked the viral RNA, and this mechanism was attributed to the reduction in survival.

Roy, Chain, (Roy, Chian, & Engelbrecht, Kinetics of Enteroviral Activation of Ozone, 1981) et al, shown that Ozone’s viricidal effect is attributed to damaging the viral RNA, through oxidation of the viral nucleic acid (RNA). The rate of viral disruption is determined by the mass transfer rate of the ozone into the viral molecules.

There is a widely found quote on the internet claiming that ozone gas has been proven to destroy surface-born SARS coronavirus. “There are more than seventeen scientific studies that show Ozone gas is capable of destroying the SARS coronavirus” (Thailand Medical news, 2020). However, these seventeen references were not provided in the document.

Modeling of Virus Destruction

A regression model of the time required to deactivate a virus using ozone and humidity was developed based the Tseng et al. data discussed above. This model was designed to provide accurate interpolation and extrapolation of the data set using the specific ozone concentrations, humidity, and time exposures encountered in field applications. Data for virus Phi X 176, which is a non-enveloped virus, were used in the regressions. This Phi X 176 basis was chosen to provide a significant measure of conservancy in the estimates (Table 2), given the enveloped Phi-6 virus is most similar to COVID-19 and much easier to deactivate.

The resultant model is:

NS/N0 = exp(-K*CT)

NS = Concentration of surface virus surviving after exposure to ozone, PFU/mL
N0 = Concentration of surface virus unexposed to ozone, PFU/ml
CT = Contact time, minutes
K = Virus susceptibility factor

The regression model for K is as follows:

K = 1.437E-7 * (ppb)^2 + 0.093147 * RH

ppb = parts per billion ozone in the gas phase
RH = relative humidity, percent

The t-statistic for the coefficients in the K model was 7.4 for the ppb term, and 2.5 for the relative humidity term, indicating that these parameters are statistically significant above the 95% confidence interval. The overall R-squared for this model is 0.993, which is exceptional.

Figure 3 is a graphical representation of the required deactivation time to achieve 99 percent removal of the virus based on this model.

The model shows how increasing ozone concentration reduces deactivation time, and that deactivation occurs faster at high humidity levels, particularly at lower ozone concentrations.


Ozone at low concentrations in the parts per billion level can be used to deactivate viruses such as COVID-19. Adding humidity can be used to accelerate the deactivation of viruses at low ozone concentrations.

Ozone has the advantage over other disinfectants that it is a gas, so that it can permeate all areas of a room, and deactivate the hardest to reach areas, including the ventilation system. Ozone has the additional advantage that it can disinfect aerosols suspended in the air. Additionally, ozone decomposes to oxygen so it is residue free.

Please feel free to contact me if you have any questions?

Rick Wilson, Ph.D.
[email protected]
(650) 704-8477


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