Ozone the Destroyer:
The Story of Ozone's Role in Disinfection
In the atmosphere, ozone plays the villain in the lower atmosphere as a pernicious air pollutant and greenhouse gas, and a hero higher up in the stratosphere where the ozone layer protects us from harmful UV radiation in sunlight. But in the deliberate hands of humankind, ozone plays a third role: versatile workhorse for the purpose of disinfection.
The Right Stuff
Why is ozone (O3) such a good disinfectant? Quite simply, because it has the right stuff. Ozone’s structure makes it a strong oxidizing agent. In the gas phase, it can react with double bonds found in many biological and organic molecules. In water, it is even more reactive and breaks down to form species such as the superoxide ion (O2-), hydroperoxyl radical (HO2) and hydroxyl radical (OH) that attack many biological molecules. These properties combine to make ozone a powerful way to eliminate organic pollutants and biological entities such as bacteria, viruses, fungi, and protozoa. In the case of bacteria, for example, ozone reacts with and breaks the cell wall (lysis), and then can also attack the essential materials within the cell such as proteins and enzymes, killing the organism. Viruses are deactivated through attacks on their surrounding fatty lipid or protein coatings, as well as their interior RNA or DNA components.
The Right Stuff
Why is ozone (O3) such a good disinfectant? Quite simply, because it has the right stuff. Ozone’s structure makes it a strong oxidizing agent. In the gas phase, it can react with double bonds found in many biological and organic molecules. In water, it is even more reactive and breaks down to form species such as the superoxide ion (O2-), hydroperoxyl radical (HO2) and hydroxyl radical (OH) that attack many biological molecules. These properties combine to make ozone a powerful way to eliminate organic pollutants and biological entities such as bacteria, viruses, fungi, and protozoa. In the case of bacteria, for example, ozone reacts with and breaks the cell wall (lysis), and then can also attack the essential materials within the cell such as proteins and enzymes, killing the organism. Viruses are deactivated through attacks on their surrounding fatty lipid or protein coatings, as well as their interior RNA or DNA components.
Not a New Idea!
Ozone’s discovery is often credited to German/Swiss chemist Christian F. Schönbein, who first wrote about it in 1840. However, owing to ozone’s peculiar and unmistakable odor, the human nose had detected ozone long before this. Even the ancient Greeks may have a piece of the history here. The word “ozone” is derived from the Greek word “ozein” which means “to smell.” Native American Indians also noticed the strange smell after lightning storms and found it improved the fishing conditions. Shortly after Schönbein’s publication, the first ozone generator was developed by German scientist Werner Von Siemens in 1857, using the discharge of an electric current from a spark coil. With this, ozone’s role as a deliberate workhorse for humankind began.
Ozone’s discovery is often credited to German/Swiss chemist Christian F. Schönbein, who first wrote about it in 1840. However, owing to ozone’s peculiar and unmistakable odor, the human nose had detected ozone long before this. Even the ancient Greeks may have a piece of the history here. The word “ozone” is derived from the Greek word “ozein” which means “to smell.” Native American Indians also noticed the strange smell after lightning storms and found it improved the fishing conditions. Shortly after Schönbein’s publication, the first ozone generator was developed by German scientist Werner Von Siemens in 1857, using the discharge of an electric current from a spark coil. With this, ozone’s role as a deliberate workhorse for humankind began.
Disinfection Using Dissolved Ozone
In the last half of the 19th Century, Europe was the epicenter for research about ozone’s chemistry and possible applications. It was quickly recognized that ozone could be used to treat drinking water, and efforts in that direction began first in the Netherlands and then were centered in France. The city of Nice in fact became known as the “birthplace of ozone for drinking water treatment.” Progress was made in ironing out difficulties in achieving sufficient ozone production and other practicalities such as ozone’s short period of efficacy after production. Alternative treatment methods using chlorine-containing compounds led to a lull in ozone disinfection for water treatment. In fact in the U.S., chlorine methods were predominant in the 20th Century.
A resurgence in the ozone method occurred though, when it was realized that chlorine methods can lead to the production of harmful trihalomethanes in water, and that ozone can eliminate some organic pollutants and protozoa that are immune to chlorine treatment. Techniques are ever evolving and a combination of ozone and chlorine treatment is used in some water treatment facilities. Beyond drinking water treatment, the uses of aqueous ozone in disinfection are numerous and in some cases surprising. Examples include wastewater treatment, swimming pool disinfection, industrial laundry operations, food industry processing, and even clinical medical applications such as surgeries and dental procedures in which dosages of ozone are administered to patients as treatments.
Gaseous Ozone as Disinfectant
As dissolved ozone proved itself to be a powerful disinfectant, the potential for applying ozone in the gas phase started to gain attention as a way to decontaminate not only air itself, but every surface in entire rooms. The possibility to make a huge advancement for human health was clearly evident. Earliest studies of ozone as an aerial disinfectant were in the early 1900s. They focused on bacteria and applied low concentrations of ozone that were tolerable to humans but that proved to be mostly ineffective. Early in these studies, humidity was identified as a factor that enhanced ozone’s disinfection capabilities, but it became clear that higher ozone concentrations (above the part-per-million [ppm] level) were needed.
Thus one barrier to ozone’s use in the gas phase is that the concentrations required for disinfection exceed health standards, such as the U.S. workplace 2-hour standard of 200 parts per billion (ppb), and are a human health hazard. “Fumigations” to disinfect must be done with care, in closed and unoccupied areas. In addition, materials such as rubber, synthetics, and paints are susceptible to damage by ozone, and byproducts of reactions with such materials might themselves be a hazard. But the enormous advantages of using ozone in the gas phase include that it is easily generated, reaches every surface in an exposure area, and quickly dissipates after fumigations. Whole rooms and all materials within the rooms (curtains, carpets, bedding, tops and undersides of furniture, corners of rooms, floors, walls, etc.) can be disinfected much more thoroughly than with labor-intensive surface “wipe-downs.” In the hospital setting, operating rooms and other critical care areas can be disinfected, and individual patient rooms can be made safe for the next patient. Any setting with close quarters and rotating occupancy, such as hotel rooms, aircraft, offices, and cruise ships, is the ideal candidate for disinfection of viruses, bacteria, and other health hazards using gaseous ozone. Ozone is itself a powerful deodorant and the disinfection treatment leaves no residual odors, unlike other methods that can have a lingering “chemical smell.”
In the last half of the 19th Century, Europe was the epicenter for research about ozone’s chemistry and possible applications. It was quickly recognized that ozone could be used to treat drinking water, and efforts in that direction began first in the Netherlands and then were centered in France. The city of Nice in fact became known as the “birthplace of ozone for drinking water treatment.” Progress was made in ironing out difficulties in achieving sufficient ozone production and other practicalities such as ozone’s short period of efficacy after production. Alternative treatment methods using chlorine-containing compounds led to a lull in ozone disinfection for water treatment. In fact in the U.S., chlorine methods were predominant in the 20th Century.
A resurgence in the ozone method occurred though, when it was realized that chlorine methods can lead to the production of harmful trihalomethanes in water, and that ozone can eliminate some organic pollutants and protozoa that are immune to chlorine treatment. Techniques are ever evolving and a combination of ozone and chlorine treatment is used in some water treatment facilities. Beyond drinking water treatment, the uses of aqueous ozone in disinfection are numerous and in some cases surprising. Examples include wastewater treatment, swimming pool disinfection, industrial laundry operations, food industry processing, and even clinical medical applications such as surgeries and dental procedures in which dosages of ozone are administered to patients as treatments.
Gaseous Ozone as Disinfectant
As dissolved ozone proved itself to be a powerful disinfectant, the potential for applying ozone in the gas phase started to gain attention as a way to decontaminate not only air itself, but every surface in entire rooms. The possibility to make a huge advancement for human health was clearly evident. Earliest studies of ozone as an aerial disinfectant were in the early 1900s. They focused on bacteria and applied low concentrations of ozone that were tolerable to humans but that proved to be mostly ineffective. Early in these studies, humidity was identified as a factor that enhanced ozone’s disinfection capabilities, but it became clear that higher ozone concentrations (above the part-per-million [ppm] level) were needed.
Thus one barrier to ozone’s use in the gas phase is that the concentrations required for disinfection exceed health standards, such as the U.S. workplace 2-hour standard of 200 parts per billion (ppb), and are a human health hazard. “Fumigations” to disinfect must be done with care, in closed and unoccupied areas. In addition, materials such as rubber, synthetics, and paints are susceptible to damage by ozone, and byproducts of reactions with such materials might themselves be a hazard. But the enormous advantages of using ozone in the gas phase include that it is easily generated, reaches every surface in an exposure area, and quickly dissipates after fumigations. Whole rooms and all materials within the rooms (curtains, carpets, bedding, tops and undersides of furniture, corners of rooms, floors, walls, etc.) can be disinfected much more thoroughly than with labor-intensive surface “wipe-downs.” In the hospital setting, operating rooms and other critical care areas can be disinfected, and individual patient rooms can be made safe for the next patient. Any setting with close quarters and rotating occupancy, such as hotel rooms, aircraft, offices, and cruise ships, is the ideal candidate for disinfection of viruses, bacteria, and other health hazards using gaseous ozone. Ozone is itself a powerful deodorant and the disinfection treatment leaves no residual odors, unlike other methods that can have a lingering “chemical smell.”
Ozone Gas versus Viruses
A 1962 study published by scientists in France might be the first to have investigated gaseous ozone as an antiviral agent on human viruses. Research in Japan in 1990 tested gaseous ozone with animal viruses, and found its effectiveness increased with length of exposure, concentration of ozone, and relative humidity. Exposures at 100-200 ppm and 80% relative humidity were effective in deactivating the viruses in ~1-2 hours. Studies in the 1990s and 2000s have confirmed and refined these findings for a variety of human viruses, bacteria, and protozoa. Humidity again was shown to speed up the antiviral action of ozone, and in some laboratory tests ozone concentrations at the ppm level were effective. Studies in real-world settings such as hotel rooms have found that exposure to ~25 ppm of ozone for an hour or less, with 90% humidity bursts during the latter part of the exposures, is effective against many different viruses including strains of influenza, herpes, rhinovirus, mouse coronavirus, yellow fever virus, and polio virus on a variety of hard and porous surfaces including glass, metal, plastic, fabric, and carpet. Field tests in offices, hotel rooms, and hospitals have demonstrated that the approach is practical in terms of the required effort and time. Commercial systems are now available, including the STERISAFE PRO developed by STERISAFE in Denmark and the Viroforce offered by Omega Environmental in the U.S.
A 1962 study published by scientists in France might be the first to have investigated gaseous ozone as an antiviral agent on human viruses. Research in Japan in 1990 tested gaseous ozone with animal viruses, and found its effectiveness increased with length of exposure, concentration of ozone, and relative humidity. Exposures at 100-200 ppm and 80% relative humidity were effective in deactivating the viruses in ~1-2 hours. Studies in the 1990s and 2000s have confirmed and refined these findings for a variety of human viruses, bacteria, and protozoa. Humidity again was shown to speed up the antiviral action of ozone, and in some laboratory tests ozone concentrations at the ppm level were effective. Studies in real-world settings such as hotel rooms have found that exposure to ~25 ppm of ozone for an hour or less, with 90% humidity bursts during the latter part of the exposures, is effective against many different viruses including strains of influenza, herpes, rhinovirus, mouse coronavirus, yellow fever virus, and polio virus on a variety of hard and porous surfaces including glass, metal, plastic, fabric, and carpet. Field tests in offices, hotel rooms, and hospitals have demonstrated that the approach is practical in terms of the required effort and time. Commercial systems are now available, including the STERISAFE PRO developed by STERISAFE in Denmark and the Viroforce offered by Omega Environmental in the U.S.
A Leap Forward in Detecting the Ozone Applied during Disinfection
With the world now in the grips of a pandemic brought on by the novel coronavirus COVID-19, ozone disinfection techniques are likely to become more widespread and to improve further. One area that has seen great advances is the method used to detect ozone during the disinfection process. An accurate and reliable measurement of ozone is critical, to assure that the ozone dosage is sufficient to deactivate viruses and other pathogens.
The earliest studies in the 1900s used a classical potassium iodide titration technique for detecting ozone—a laborious approach and certainly not a “real-time” method. Techniques for detecting ozone have advanced, and other methods are now used during disinfections. One inexpensive approach has used electrochemical and metal oxide sensors. However, sensors generally are not sufficiently accurate or precise, and they have numerous drawbacks such as baseline and sensitivity drift, non-specific response to ozone, and insufficient range of detection. In addition, they can malfunction in high humidity—one of the environmental conditions found to be critical to ozone’s antiviral effectiveness. These factors combine to make currently available sensors unsuitable for use with ozone disinfection systems.
Today, the use of ozone monitors based on the UV-absorbance technique has advanced the precision and reliability of the measurement beyond all previous methods used in ozone disinfection. 2B Technologies has played a part in this advance. Our Model 108 Ozone Monitors are integral to commercial ozone disinfection systems, including those used in medical settings, such as the STERISAFE PRO, and those developed for food safety processing, such as systems made by Purotecs, Inc. The instrument enables precise measurements of ozone across the wide range of ozone concentrations used throughout the disinfection process (20-200 ppm for whole-room exposures, and recovery to safe levels <200 ppb). Thus the 2B Tech Model 108 provides information that is vital to determining whether effective concentrations of ozone are being applied, as well as signaling when concentrations are low enough to safely re-enter a room following a fumigation.
2B Technologies is proud to be on one of the front lines of the virus wars.
With the world now in the grips of a pandemic brought on by the novel coronavirus COVID-19, ozone disinfection techniques are likely to become more widespread and to improve further. One area that has seen great advances is the method used to detect ozone during the disinfection process. An accurate and reliable measurement of ozone is critical, to assure that the ozone dosage is sufficient to deactivate viruses and other pathogens.
The earliest studies in the 1900s used a classical potassium iodide titration technique for detecting ozone—a laborious approach and certainly not a “real-time” method. Techniques for detecting ozone have advanced, and other methods are now used during disinfections. One inexpensive approach has used electrochemical and metal oxide sensors. However, sensors generally are not sufficiently accurate or precise, and they have numerous drawbacks such as baseline and sensitivity drift, non-specific response to ozone, and insufficient range of detection. In addition, they can malfunction in high humidity—one of the environmental conditions found to be critical to ozone’s antiviral effectiveness. These factors combine to make currently available sensors unsuitable for use with ozone disinfection systems.
Today, the use of ozone monitors based on the UV-absorbance technique has advanced the precision and reliability of the measurement beyond all previous methods used in ozone disinfection. 2B Technologies has played a part in this advance. Our Model 108 Ozone Monitors are integral to commercial ozone disinfection systems, including those used in medical settings, such as the STERISAFE PRO, and those developed for food safety processing, such as systems made by Purotecs, Inc. The instrument enables precise measurements of ozone across the wide range of ozone concentrations used throughout the disinfection process (20-200 ppm for whole-room exposures, and recovery to safe levels <200 ppb). Thus the 2B Tech Model 108 provides information that is vital to determining whether effective concentrations of ozone are being applied, as well as signaling when concentrations are low enough to safely re-enter a room following a fumigation.
2B Technologies is proud to be on one of the front lines of the virus wars.
