Understanding ozone disinfection technology with STERISAFE

Ozone disinfection technology has received increasing attention – but how do we separate the wheat from the chaff?

The current COVID-19 outbreak has prompted a growing interest in innovative disinfection technology. Notably, the potential benefits offered by disinfection technologies that use ozone are garnering attention.

This level of attention has contributed to creating an environment of opportunistic behaviour wherein multiple companies imply that their inexpensive and small ozone disinfection products can be used to remove bad odors, harmful pathogens, particles, bacteria, and in some cases, even SARS-CoV-2. However, these claims are at best debatable, if not erroneous. The efficacy when using ozone is highly dependent on several factors, including:

  • Ozone concentration
  • Contact time between ozone and targeted microorganisms
  • Relative humidity
  • The inherent resistance of the targeted microorganism.

In complex room settings, several other factors also play a significant role when it comes to efficacy. This includes air circulation and the homogenous distribution of the disinfecting agents.

Inexpensive solutions circulating the internet often do not live up to basic requirements or possess the adequate technology needed to make any thorough disinfection possible. When a global pandemic is roaring, individuals and organisations will attempt to reduce infection rates by following government guidelines. However, many wishes to go beyond those guidelines and expand safety protocols for the sake of customers, clients, employees, and themselves. These attempts could include the acquisition of simple and inexpensive ozone generators as these products position themselves as a remedy against unwanted viruses.

Only a narrow range of customers in possession of the appropriate knowledge are fully aware of their obligations when using ozone as a disinfection tool. However, the absence of any specific legislation or regulation regarding the sale of ozone disinfection technology enables rogue companies to target many potential uninformed customers and to sell them products that do not provide the promised results. Vague claims with no third-party verification can lead to improper use of ozone, create serious health hazards, and a dangerous illusion of protecting people from disease.

It is important to stress that the use of ozone should not be taken lightly. In developing and creating an ozone-based disinfection technology, STERISAFE has acquired expert-level knowledge regarding this subject. STERISAFE is a company located on the campus of the University of Copenhagen since 2014 and have developed a unique and patented technology to perform effectively, safe, and rapid automated room disinfection. From the very beginning, the mission has been to limit the increasing threats of Healthcare Acquired Infections (HAI). Nevertheless, the technology is now in use for infection prevention in several industries.

Recent tests by third-party laboratories confirmed, that STERISAFE’S disinfection robot: the STERISAFE PRO was affective against corona virus type, and since then, STERISAFE began a new journey trying to fight the global COVID-19 pandemic with ozone-based disinfection.

Since whole room disinfection is becoming an inevitable necessity in many settings, it is crucial to relay the current findings regarding the ineffective and, at times, dangerous products that are found when conducting a simple Google search. The distribution of disinfection technologies comes with a big responsibility towards clients and communities that rely on such technology to keep them safe.

Necessary features and abilities to consider when researching ozone disinfection units

Any ozone-based equipment should provide its customers with clear information on safety measures, the scope of usage, and adequately documented and proven claims. Unfortunately, many manufacturers fall far short of these requirements. Previous studies performed in particularly malodorous environments reported that ozone was only effective at removing part or selected groups of foul-smelling compounds at lower concentrations. It is suggested that a more significant reduction of smelling compounds would occur only at ozone levels higher than permissible exposure limits. Moreover, ozone can impair one’s sense of smell. The sensation of freshness after using a household ozone generator would be mostly due to a masking effect rather than actual removal of odor and virus.

From a technical standpoint, STERISAFE PRO is equipped with several components that ensure that every disinfection cycle is carried out effectively and, most importantly, safely. One of the critical aspects of STERISAFE’s Full-Depth Disinfection Cycle (FDDC) is its constant real-time monitoring of the ozone concentration in the sealed, disinfected room. This is important in order to validate that the room has been exposed to concentrations high enough to kill pathogens and why no one should be in contact with the ozone during the disinfection process. The STERISAFE PRO is equipped with an optic-based ozone monitor. It updates at regular intervals and ensures that the disinfection cycle is progressing under the proper conditions to warrant full efficacy.

A sensor feedback loop is used to monitor and control the humidity in the room at all times: a higher relative humidity allows for a better reactivity of ozone. This synergy makes both ozone concentration and relative humidity essential parameters for antimicrobial activity. While levels for both parameters are predetermined by extensive research regarding efficacy, a real-time monitoring and control function is imperative to guarantee that every cycle is conducted appropriately and without issue.

Even though ozone is a key player in disinfection technology, it is only useful and safe when integrated into a more extensive process

Equally essential to constant monitoring is the ability to produce ozone in a reliable manner and without by-products. The STERISAFE PRO uses an oxygen concentrator, which generates ozone from oxygen purified from ambient air. Having this intermediary step permits not only a stable, high throughput of ozone at approximately 40 g/h, but also removes naturally occurring nitrogen from the ozone production. This ensures that no harmful nitrogen oxide (NOx) gases – a family of common air pollutants – are released along with ozone, which is a common problem among inexpensive and simple air-fed ozone generators. The STERISAFE PRO has a powerful built-in fan that distributes the ozone homogeneously in all corners of the room. This ensures whole room disinfection, including all small cracks and corners.

Disinfection processes release particulate matter (PM), which is also considered harmful due to the small size of by-product particles and the damage they can cause upon inhalation. These particles are also a common consequence of the reaction between ozone and volatile compounds. To address this issue, the STERISAFE PRO is equipped with an electrostatic precipitator (ESP), which role is to trap and collect such particles at the end of every cycle. Manufacturers typically ignore this issue, and lower-end ozone generators systematically cause a surge in airborne particle concentration.

After the disinfection cycle, the STERISAFE PRO reverses its process turning residual oxidants back into pure oxygen while also removing all particles and nano-particles. There are no remaining compounds or harmful by-products left behind by the end of this process, and it is then entirely safe to enter and use the room as usual.

Appropriate standards and testing, and why they are reliable

Only products that have gone through thorough quality testing and vetting by competent authorities should enter the market. Unfortunately, this is far from being the case. The NF T 72-281 standard is a protocol designed by the French standardisation body AFNOR. It is designed for airborne surface disinfection systems, and it is recognised for its particularly strict fulfillment conditions. NF T 72-281 defines a set of testing methods to challenge disinfectant products in real-life circumstances. The efficacy data of the product is obtained once tests have been conducted according to the intended manner of use.

AFNOR published the first version of NF T 72-281 in 1980 and has updated it several times since, with the latest iteration being in 2014 (NF T 27-281:2014). The necessity for this standard lies in the unsuitability of existing standardised test methods for biocidal materials delivered via air. Current European standards (EN) testing for the efficacy of disinfecting agents only test by direct application methods; meaning the allegedly biocidal product is in liquid form, and either submerged or directly entering in contact with target microorganisms. Those types of testing are usually considered type “Phase 1”; and while they are a good indicator of the tested substances’ biocidal nature, Phase 1 tests are not representative of the real-life usage of biocidal agents. This is a particularly important distinction in the case of airborne disinfectants. Active agents are delivered as gas, vapour, mist, or fog, and have completely different parameters of action (concentration, surface contact, and time).

Because regulatory bodies are aware of this issue, they currently use NF T 72-281 as the starting point for a new EN standard dedicated to airborne disinfection systems (EN 17272). Meanwhile, the Biocidal Products Regulation (BPR, Regulation (EU) 528/2012) only accepts the NF T 72-281 standard for airborne surface disinfection systems. When choosing an airborne disinfecting instrument, it is highly recommended to select a product that uses the NF T 72-281 standard for its efficacy claims. Manufacturers of airborne disinfecting materials that base their efficacy claims on unsuitable EN standards provide inapplicable figures, which can potentially put a health threat to the user and the environment.

As for all microbiology tests, NF T 72-281 measures efficacy against a logarithmic scale. Microorganisms are counted as numbers of colony-forming units (CFUs), and effectiveness is given as the difference between the CFU count before and after application of the disinfecting agent. The result is given as a number of ‘log-reduction’, where a log-reduction of one corresponds to a 10-fold reduction. For example, for a 106 initial CFU, a log-reduction of four would see a decrease of 102 CFU after treatment. This is typically marked on commercial packaging as a kill-rate percentage, where a log-two reduction corresponds to a 99% germicidal power, a log-three to 99.9%, and so forth.

NF T 72-281 is defined as a methodology for the “determination of bactericidal, fungicidal, yeasticidal, mycobactericidal, tuberculocidal sporicidal and viricidal activity, including bacteriophages”. The biocidal efficacy requirements depend on the target organisms:

  • Bacteria: > five-log reduction
  • Spores: > three-log reduction
  • Fungi & yeasts: > four-log reduction
  • Viruses incl. phages: > four-log reduction
  • Mycobacteria: > four-log reduction

Achieving results, safety, and protection

STERISAFE uses the NF T 72-281 standard for all its products and can guarantee their efficacy. Considering the test conditions, the high kill-level objectives it requires, and its extensive target range, the NF T 72-281 should be the only acceptable standard methodology for airborne disinfectant products’ efficacy claims. STERISAFE has been a pioneer in using this standard in the industry of the ozone-based disinfection systems and will continue to do so.

Ozone can be a remarkably useful component in a disinfection cycle. When ozone disinfection is conducted correctly and safely, there should not be any concerns connected to its use. However, potential users are strongly encouraged to question a disinfection product, which seems too good to be true. Excellent solutions, which fulfil both safety and efficacy requirements, are available on the market. The most crucial step is to research individual products and companies to ensure that their technology and data are adequate to the user’s specific needs. This information can function as a guideline for what to be attentive to in one’s search for disinfection technologies.

Author: Amanda Johnsen & Sorivan Chhem-Kieth

Researchers have proved that ozone is effective in disinfecting coronavirus.

By: Tel-Aviv University

Researchers have proved that that ozone is effective in disinfecting Coronavirus

Studies have shown that SARS-CoV-2 remains active on aerosols and surfaces for between several hours and several days, depending on the nature of the surface and environmental conditions. Presently, researchers from Tel Aviv University have demonstrated that ozone, which has already long been used as an antibacterial and antiviral agent in water treatment, effectively sanitizes surfaces against Coronavirus after short exposure to low concentrations of ozone. The research team was led by Dr. Ines Zucker from the School of Mechanical Engineering at the Ivy and Eldar Fleischman Faculty of Engineering and the Porter School of the Environment and Earth Sciences at the Tel Aviv University. Dr. Zucker collaborated with Dr. Moshe Dessau from the Azrieli Faculty of Medicine at Bar Ilan University in the Galilee and Dr. Yaal Lester from the Azrieli College in Jerusalem in order to investigate the feasibility of ozone for indoor inactivation of SARS-CoV-2.

The preliminary findings of the study were published in the Journal: Environmental Chemistry Letters.

Most people recognize ozone as a thin layer of the Earth’s atmosphere that guards us against the harmful effects of UV radiation. However, ozone is also known as a strong oxidant and disinfectant employed in water and wastewater treatment schemes. Within the study framework, the research team decided to adapt the mechanisms whereby they use ozone to break down organic pollutants from contaminated waters and demonstrate the expected efficacy of the ozone in neutralizing Coronavirus.

Ozone gas is generated by electrical discharge (the breakdown of chemical compounds into their elements using electric current), in the course of which oxygen molecules are reconstructed in the form of ozone molecules. In the course of their study, the researchers demonstrated the inactivation from various infected surfaces, even in hard-to-reach locations. They demonstrated a high level of disinfection within minutes, even on surfaces not typically disinfected with manually-applied liquid disinfectants with a statistical success rate of above 90%. According to Dr. Ines Zucker, the method involves inexpensive and readily available technology, which can be utilized to disinfect hospitals, schools, hotels, and even aircraft and entertainment halls.

Researchers have proved that that ozone is effective in disinfecting Coronavirus
Dr. Ines Zucker. Credit: Tel Aviv University.

“Gaseous ozone is generated from oxygen gas by electrical discharge. Now, for the first time, we have managed to prove that it is highly efficient in combating Coronavirus as well,” stresses Dr. Zucker. “Its advantage over common disinfectants (such as alcohol and bleach) is its ability to disinfect objects and aerosols within a room, and not just exposed surfaces, rapidly and with no danger to public health.” Dr. Zucker estimates that, since the gas can be produced relatively cheaply and easily, it should be possible to introduce ozone disinfecting systems on an industrial scale to combat the COVID-19 outbreak.

Sourced from: https://phys.org/news/2021-02-ozone-effective-disinfecting-coronavirus.html

Water disinfection with ozone gains traction

While chlorine and ultraviolet light are the standard means of disinfecting water, ozone is equally effective in killing germs. To date, ozone has only been used as an oxidation agent for treating water in large plants. Now, however, a project consortium from Schleswig-Holstein is developing a miniaturized ozone generator for use in smaller applications such as water dispensers or small domestic appliances. The Fraunhofer Institute for Silicon Technology ISIT has provided the sensor chip and electrode substrates for the electrolysis cell.

Compared to conventional means of disinfection such as chlorine or ultraviolet, ozone dissolved in water has a number of advantages: it is environmentally friendly, remains active beyond its immediate place of origin, has only a short retention time in water and is subsequently tasteless. Due to its high oxidation potential, ozone is very effective at combating germs. It breaks down the cell membrane of common pathogens. In Germany, ozone is chiefly used to disinfect swimming pools and drinking water and to purify wastewater. Yet it is rarely used to disinfect water in domestic appliances such as ice machines and beverage dispensers or in other fixtures such as shower-toilets. MIKROOZON, a project funded by the State of Schleswig-Holstein and the EU, aims to change this. Researchers from Fraunhofer ISIT have teamed up with the Itzehoe-based company CONDIAS GmbH, which was founded in 2001 as a spin-off from the Fraunhofer Institute for Surface Engineering and Thin Films IST, and CONDIAS partner Go Systemelektronik GmbH, from Kiel. The three partners are developing a miniaturized ozone generator with integrated sensor technology and microprocessor control system.

Direct production of ozone via water electrolysis
“The ozone generator is very compact and can be integrated in systems and appliances that require regular disinfection,” says Norman Laske, researcher at Fraunhofer ISIT. “You simply connect it up to the water line, and it will produce the right amount of ozonized water whenever required.” The ozone generator is only a couple of cubic centimeters in size and comprises an electrolysis cell, a sensor chip, control electronics to regulate current and voltage, and electronics to read the sensor signals. “The two electrodes are separated by an ion-conducting separator membrane,” Laske explains. “When a voltage is applied across the electrodes, the water is split by a process of electrolysis. Because of the diamond layer coating the electrodes, this process first forms hydroxyl radicals, which then react to form primarily ozone (O3) as well as oxygen (O2).”

The electrodes for the ozone generator are made of silicon wafers with precisely etched trenches.

The electrodes for the ozone generator are made of silicon wafers with precisely etched trenches. Credit: Fraunhofer-Gesellschaft

Diamond-coated silicon electrodes
How the electrodes with their boron-doped diamond layer are made is the know-how that has given CONDIAS GmbH its name. The company already uses a chemical vapor deposition process to coat large-scale electrodes required to disinfect the ballast water of marine vessels. However, the electrodes required for the MIKROOZON generator are much smaller. They are made of silicon and have finely etched trenches that run through the electrodes to form narrow slits on the reverse side. In order to be able to etch these trenches with the required precision, the researchers from Fraunhofer ISIT had to have wafer material manufactured to their own specifications.

To build an ozone generator, pairs of these electrodes are mounted back to back, with a separator membrane between them. The gases are released at the interface to the separator membrane and then escape through the trenched structure to the other side of the electrode, where the turbulence of the water flow ensures that they are efficiently dissolved and dispersed.

The sensor chip from Fraunhofer ISIT is equipped with three sensors to measure conductivity, mass flow and temperature. These parameters need to be monitored in order to control the electrolytic process. The sensor chip provides the data that is required to control ozone production in line with the quality and the amount of water used. “In order to ensure that there is enough ozone available over the period required, the temperature has to be monitored,” Laske explains. “This is because ozone decomposes more quickly at higher temperatures.” Conductivity correlates to the degree of water hardness: the harder the water, the higher the conductivity—meaning that more current must flow in order to achieve the desired effect. When equipped with a system to monitor these parameters, the ozone generator should be capable of processing up to 6 liters of water per minute—without the sensor chip, it is currently specified for 0.5 to 1.5 liters.

CONDIAS is marketing the mini-generator under the brand name of MIKROZON. “Each partner has contributed years of experience from their own area of specialization,” says Volker Hollinder, CEO of CONDIAS GmbH. “This has created a product that can now be manufactured on an industrial scale. The spread of the coronavirus has underlined the importance of disinfection. The use of chemical disinfectants is often problematic, because they leave harmful residues. Our system uses electrolytically generated ozone to eliminate germs. It therefore does not produce any residues from disinfectants.”

Source:  Fraunhofer-Gesellschaft

A Gallon of 3ppm Aqueous Ozone for Sale



Ozonated water, bleach, and hydrogen peroxide are three oxidizing agents useful for disinfection, odor control, color removal, water treatment, food preparation, and more. Bleach and hydrogen peroxide are common, low cost household items, but you will never find a gallon of ozonated water in the store even though it has many superior qualities. Equipment can be purchased to make a gallon of aqueous ozone, but how does the price compare to hydrogen peroxide or bleach? Let’s figure it out.

Oxidizers pack stored up molecular energy that breaks apart odor and color molecules. The energy is released on contact and physically disables or destroys microorganisms and viruses. Bleach, a combination of chlorine and oxygen, is valuable because it is stable and will oxidize over a long length of time. Hydrogen Peroxide, a water molecule with one extra oxygen atom, can also be stored and its oxidizing power applied when needed. Ozone molecules combining 3 atoms of oxygen are dissolved in water to produce ozonated water,, better known as aqueous ozone. The ozone immediately reacts with any contaminants in the water and breaks down to oxygen over a matter of minutes.

Oxidizers are very useful for solving everyday problems. You can find a bottle of 3% hydrogen peroxide in most households, and barrels of 35-50% peroxide in many different industries. Even more common is a gallon of bleach. The power and value of oxygen is well-known, and the convenience of having this power in a jug of hydrogen peroxide or bleach is very attractive. A gallon of aqueous ozone also contains this oxidating power, and its uses are diverse and growing. You will not find a gallon of ozonated water for sale because it has a shelf life of minutes. It is highly reactive and therefore quickly dissipates back to oxygen within a matter of minutes. The only way to get this powerful tool is to make it as needed with electricity.

Before discussing the equipment needed to ozonate water, we will explore some of the ways it can be used. Ozone dissolved in water has been used for over 100 years in large scale industrial settings, but a growing number of people are discovering the value of ozonated water in smaller applications. The demand for environmentally friendly and healthy solutions to problems is driving the demand for ozonated water and the technology to provide it.

Bacteria and mold is an age-old problem for food preparation and storage. Aqueous ozone provides an attractive alternative to chemicals that may alter taste or lead to health problems. Aqueous ozone has the power to destroy bacteria as well as improve taste, smell, and appearance of many foods. A gallon of aqueous ozone can
1) Rinse a bushel of cranberries to prevent a 20% loss due to mold
2) Extend the shelf life of 20 pounds of fresh fish
3) Make 10 gallons of freshwater safe to drink
4) Provide a Log 3 reduction in bacteria count on three butchered chickens
5) Disinfect a wine carboy
6) Disinfect food preparation equipment
7) Disinfect cow udders before or after milking

Ozone will enhance the value of polluted water by helping to remove many contaminants. Ozone dissolved into a gallon of polluted water has the power to
1) Remove discoloration
2) Oxidize dissolved iron for filtration
3) Clean aquaculture water
4) Lower the chemical cost of cooling tower operation
5) Wash clothes in cold water.
6) Treat a pool or spa.
7) Remove pathogens and add oxygen for hydroponics.

This list only scratches the surface of possibilities. Many of the uses people have found for hydrogen peroxide can be accomplished with aqueous ozone. While the convenience of stored oxidative power is attractive, there are also advantages to having this power on tap. An ozone water system makes this possible, and the value may be surprising.

This brings me back to the question: how much would you pay for a gallon of ozonated water? Let’s suppose you were willing to pay somewhere between the $0.02 for bleach or $3 for the hydrogen peroxide option … $1 a gallon. Our OXS-10 ozonated water system can produce about 10 gallons of 3 ppm ozonated water per minute. At that rate, it would make 600 gallons an hour, or a value of $14,000 per day. Even at $0.05 a gallon, an OXS-10 system generates a value of $700 per day.

If you did not need that much aqueous ozone, and just wanted a few gallons to rinse produce for your family or wash clothes, some different options are available. The simplest way to prepare some ozonated water is to use a small ozone generator and a bubble stone. Bubbling ozone in a gallon of water using a small ozone generator can dissolve some ozone in water, but it is not very efficient and is difficult to attain 2 ppm without dealing with significant off-gas. Even so, many people do this and are happy with the results.

Electrolytic devices are under development and available to provide up to 2 ppm aqueous ozone from a handheld spray bottle or from a kitchen tap. They generate ozone directly from water by running an electric current to special electrodes in the water. Electrolytic devices are convenient, but over time the electrodes get fouled with minerals and ozone output levels decline. Regular cleaning with a vinegar solution restores their function.

The SB-100 spray bottle is a convenient way to apply a spray of ozonated water over a kitchen counter or for rinsing produce. When used with clean water and given a regular vinegar rinse, the spray bottle will provide 1000-2000 hours of use. It sprays 1/2 a cup of ozonated water a minute at up to 2ppm concentration. That would be 30 cups an hour or about 2 gallons an hour. Over its expected life, it will provide up to 4000 gallons of ozonated water. With a price tag of $499, the cost of a gallon of ozonated water from the convenience of a spray bottle comes to between $0.12 and $0.25.

Another option is a small battery powered pen-sized device – the O-Pen which provides a convenient way to disinfect a 16-ounce glass of water in one minute. This is equivalent to 960 ounces or 7.5 gallons per hour. Over its expected life, it has the capacity to ozonate 7500 to 15,000 gallons of water. The O-pen can be purchased for $150, so the cost of a gallon of ozonated water comes to $0.02 to $0.01 per gallon.

The OZO-Pod is capable of bringing a gallon of water up to 2-3ppm within a minute. At $189, this device is capable of providing a gallon of ozonated water at less than a penny a gallon.

Electrolytic devices provide a very simple and convenient means for making small amounts of ozonated water. They are prone, however, to fouling problems if the water quality is poor. The most reliable, long-term equipment for producing larger amounts of ozonated water consists of a high concentration ozone generator supplied with dry air or an oxygen concentrator and an injection venturi with off-gas tank. Most hot tubs have a small ozone generator with a venturi built into the circulation plumbing. A variety of options using this technology are available for home laundry applications as well.

The WT-4 ozone water system can produce 300 gallons of 1-2 ppm water for pennies a gallon over its expected life. Our industrial line of ozone water systems (OST series, OXS series, ISX series) are capable of providing much higher concentrations of dissolved ozone if needed. The ISX system can provide up to 500 gallons per minute. We also provide service and larger equipment for municipal water treatment plants.

At a penny a gallon, making 500 gallons of aqueous ozone a minute generates a value of at least $300 an hour and breaks a million dollars in value after only 5 months of operation. Hydrogen peroxide and Clorox have their place, but ozonated water is a very competitive option to supplement or replace these oxidants.

In summary, the base price for a gallon of aqueous ozone is anywhere between $0.01 and $0.25 depending on the type of equipment used. In general, a lower initial cost of small equipment will mean a larger price per gallon because it makes less ozone and doesn’t last as long. Top quality industrial equipment will be expensive, but will make large quantities of aqueous ozone and last a long time.

The actual cost of a gallon of aqueous ozone needs to include the cost of a gallon of potable water and maintenance costs for the machine. The average price for a gallon of potable water is $0.01. Even if the spray bottle at $0.25 a gallon only lasted half its expected life, you could have gallons of aqueous ozone for under $1 a gallon. Maintenance and time spent on larger machines would at the most double the cost of aqueous ozone and still be only pennies a gallon.

We can make a better price comparison to hydrogen peroxide and bleach if we dilute the typical 3% peroxide to 1%. This would have similar oxidizing power to 3ppm aqueous ozone. We can make a 100 ppm bleach solution to get an equivalent for bleach. Doing this we have the following table for comparison:

1 Gallon of 1% hydrogen peroxide $3

1 Gallon of 3 ppm ozonated water – $0.03 – $0.25

1 Gallon of 100ppm bleach solution – $0.02