Why Ozone is the Gold Standard for Disinfection of SARS-Contaminated Areas?

Why is it important to disinfect the air?

Do we truly need to disinfect the air?

  • The outbreak of SARS worldwide in March 2003 began to generate more awareness of the transmission of airborne respiratory diseases in indoor environments. Evidence(1) demonstrates that SARS and SARS types Coronavirus can survive in exhaled respiratory droplets for up to several days.
  • This means the people breathing air that contains these droplets are at much higher risk of infection and contracting these diseases. Because this holds true, new methods are needed for new reliable and efficient air disinfection methods to be used when decontaminating these high-risk areas.

Existing Modalities for air disinfection

  • One of the most common methods employed it the use of ultraviolet (UV) radiation. When given a long enough exposure to UV radiation (UV-C) kills viruses and bacteria by damaging the DNA/RNA inside the microorganism’s cells. Unfortunately, due to the long dwell time requirements, UV radiation is only able to disinfect air close to the lamps because UV light has limited penetration capacity and the airborne viruses and bacteria don’t get exposed for long enough. Another issue is one of shadows. UV light and typically only treat the top sides of objects in a room being treated. All buildings contains nooks and crannies and three dimensional interfaces where viruses, bacteria, nano-bacteria and spores can hide. In case of a SARS or respiratory type coronavirus contaminated room, UV disinfection alone is not adequate to provide virus-free environment, there are shadowed areas hidden from light and tiny inaccessible spaces where the pathogens can are hiding.
  • With the recent coronavirus outbreak, well-known air cleaning methods are being touted like the employment of High Efficiency Particulate Air (HEPA) filters. While true that HEPA filters can capture particulate sizes down to 0.3 microns, some bacteria with sizes larger than 0.3 microns are able to be captured by the filter, however viruses, nanobacteria, mycoplasmas and more go sailing right through them like water through cheese cloth. Although HEPA filters are somewhat effective in reducing airborne bacteria, theyare completely ineffective at removing viruses, which are nanometers (10-9 m) in size. Also, in order for air to be filtered or cleaned it must pass through the filter itself. This means that HEPA filters can only filter the air that is close to the return vent of the filter itself. There a multiple flaws in attempting to use HEPA filters for virus elimination and containment principally the tiny size of tviruses themselves and the inefficiencies inherent in HVAC design.These multiple drawbacks make HEPA filters unreliable for removal and disinfection of SARS coronavirus contaminated areas.
  • Chemical disinfectants can also be used for air and surface disinfection, and are typically fogged, sprayed or wiped onto surfaces. However, these chemical disinfectants pose just as many challenges. In order for most of them to work or to be effective at killing or disinfection they must leave the surfaces wet for up to ten minutes. This is impracticle and is rarely done, infact if it were done the water left behind after the active killing is accomplished becomes potential microbial food if the products are indeed biodegradable. If the products are not biodegradable they are often difficult to degrade or break down, and this results toxic chemical residues being left behind and pose additional risks as they remain hazardous to human health.
  • In 2002 Scientists at Los Alamos National Laboratory were tasked with developing a protocol for disinfecting aerosolized microbial contamination, specifically anthrax spores. They discovered that there was no one step panacea, but that using the above traditional approaches also left behind contaminated structures due to the hidden three dimensional interfaces that exist in all buildings where the viruses bacteria and spores can hide. Instead the researches put forth the hypotheses that the only way to truly decontaminate a building was to fill it full of ozone gas in what is known as a high concentration ozone shock treatment. Ozone is a well-documented method to kill microorganisms effectively because it is a potent oxidizer. Ozone is widely used to sanitize water and is used in modern wastewater treatment plants and in cities all around the world. Recent studies demonstrate that using ozone to disinfect indicate in experimental results (2,3) that ozone can be as effective in disinfecting air as it is in water. For example, Kowalski et al (2) investigated the bactericidal effects of high ozone concentrations on E. coli and S. aureus and concluded that more than 99.99% death rate was achieved for both species after ozonation.
  • In addition to it’s immense killing power, it kills germs more than 3,125x faster than chlorine bleach, ozone’s gaseous nature makes it an ideal airborne sanitizer. In fact it was entered into the Federal Register in 2001 as a USDA Organic Label Program approved sanitizer in both it’s aqueous and gaseous forms. As opposed to the limitations UV radiation and HEPA filters which are proven to be ineffective, ozone as a gas is easily able to penetrate into to every nook cranny crevice and hidden cul de sac in the structure, easily sanitizing the entire room effectively. Ozone is unstable, and has an extremely short half life, therefore when the ozone generator is turned off within minutes it is readily converted back to normal oxygen, leaving behind no harmful residues after sanitization is complete.
  • Ozone has not only been proven to be effective in the laboratory setting it is also has been used effectively in a multitude of real world settings to both sanitize the air and surfaces. Here, we share the efficacy of ozone treatment for SARS type corona virus, the effectiveness of ozone in disinfection of a conference room.
  • Disinfection capacity of ozone

    • Ozone (O3) is a highly reactive gas made up of three atoms of oxygen. It is reactive because the gas will easily degrade back to its natural state,or normal stable oxygen (O2). What really does the work when it comes to ozone is the extra free oxygen atoms or free radicals. Free radicals are highly reactive and they can oxidize almost anything (including viruses, bacteria, organic and inorganic compounds) after short periods of contact, which makes ozone an incredibly powerful oxidizing sanitizer or disinfectant.
    • In fact, ozone is far more powerful and reactive than other common disinfectants such as chlorine and hypochlorite, it kills germ over 3000x faster. Unlike chlorine or hypochlorite ozone doesn’t degrade into other toxic by-products. Due to the possibility formation of carcinogenic by-products such as trihalomethanes (THM) chlorine or hypochlorite are no longer being used in many countries.
    • In contrast, ozone rapidly degrades into pure oxygen and doesn’t generate similar toxic residue. Because ozone harnesses the power of oxygen and doesn’t generate toxic by-products. Ozone has become one of the dominant water treatment methods in Europe and in the United States of America, due to the lack of toxic byproducts. Ozone for air sanitization is less popular than the in water because ozone is harmful to the lungs to breathe, therefore all air treatments must be done in unoccupied spaces.

    Procedure for air disinfection using ozone

    • In order to test for the effectiveness of ozone in reducing airborne bacteria, a conference room with area about 12m2 was selected for testing. As high levels of ozone are required to kill viruses, bacteria and mold spores, the disinfection process was carried out in an unoccupied space, after people, plants and pets were removed.
    • In order to reach shock treatment levels a high output ozone generator is needed like the Bioblaster, from www.bestozonegenerator.com The capacity of the chosen ozone generator must have the capacity to generate high ozone levels of at least (2.5 – 5 ppm) inside the treatment area. Depending on the model use circulation fan may need to be placed in the room to ensure through distribution of ozone. After closing all the windows and doors, the ozone generator was turned on with a remote control located outside of the treatment area before beginning the ozonation. Concentration of ozone was monitored using a digital ozone meter (Ecosensor). Different levels of ozone (0.5, 2.5 and 5 ppm) were tested to determine the optimal value for killing as much microorganisms as possible. After turning off the ozone generator, ozone level began to drop as it degraded to normal oxygen.
    • For safety reasons, no people should enter the room until the level of residual ozone is below 0.02 ppm. In general, ozone concentration drops to below 0.02 ppm in an hour after ozonation, therefore people should wait for at least one - two hours (after turning off the generator) before entering the “shock ozone treated” room.
    • Figure 1 shows a typical curve (concentration vs. time) during ozonation process. As shown in the figure, the ozone concentrations increase very slowly initially in the first few minutes. The delay in increasing the ozone concentration is due to the consumption of ozone for oxidizing pollutants (including bacteria and viruses) in the initial period. After oxidizing the major pollutants, ozone concentration inside the room rises rapidly up to the desired level. To ensure entire room disinfection, high levels of ozone were maintained for 30 minutes. When the ozone generator was turned off, the ozone concentration dropped gradually as ozone converted back to pure oxygen.

    Effectiveness of ozone on reducing airborne bacteria

    The total airborne bacteria in the conference room was measured before and after each shock ozone treatment. Measurement was carried out using an Andersen N-6 single-stage sampler with Tryptone Soya Agar (Oxoid) in petri dish. 283L of air was taken for each sampling. The petri dish was incubated at 35oC for 48 hrs before counting. The disinfection efficiency of ozonation at different concentration was tabulated in Table 1.

    Table 1. Reduction of Airborne Bacteria after Ozonation

    • The results of the testing prove that ozone is effective in at reducing and killing the bacteria . At higher ozone levels, the sanitizing effect increased. Over 90% of airborne bacteria could be reduced at 2.5 ppm concentration.
    • Unlike laboratory experiments conducted by Kowalski et al (1) that removed 99.99% airborne bacteria after high ozone shock treatment, in this experiment the best reduction percentage in our case was around 93% only. The reason for this is thought to be because the conference room was not 100% sealed and the HVAC system introduced new bacteria laden air via the make up air intake on the system. Also doors were opened briefly during each air sampling (for placing a new agar dish on the sampler) and the aforementioned air exchange from outside was unavoidable.


    Experimental data shows that ozone is effective in reducing airborne bacteria of unoccupied room. Over 90% of airborne bacteria in this real world experiment were reduced after ozone shock treatments. Viruses are more susceptible to ozone than bacteria because bacteria are protected by a cell wall. Ozone has been demonstrated to easily damage the protein lipid coating on the surface of the virus and it damages the RNA replication mechanism of all viruses. This means it is ideal for the destruction Ozone is a gas, and as a gas can permeate the tiniest hidden place in a room or facility, and with powerful oxidizing power, its disinfection efficiency is superior to UV radiation and unlike HEPA filters it actually works! Since ozone shock treatments are performed in unoccupied rooms only and all the residual ozone breaks down naturally after the treatment, so it is perfectly safe for humans. With the tremendous oxidization power and it’s penetration capacity leaving behind residues after the treatment, ozone is recommended for use in disinfection of SARS-contaminated environments.


    • Gérard V. Sunnen, SARS and Ozone Therapy: Theoretical Considerations, http://www.triroc.com/sunnen/topics/sars.html (2003).
    • W. J. Kowalski, W. P. Bahnfleth, and T. S. Whittam, Ozone Sci. & Eng., 20, 205-221 (1998).
    • T. Masaoka; Y. Kubota, S. Namiuchi, T. Takubo, T. Ueda, H. Shibata, H. Nakamura, J. Yoshitake, T. Yamayoshi, H. Doi, T. Kamiki, Appl. & Environ. Microb., 43, 509-513 (1982).
    • Development of a Practical Method for Using Ozone Gas as a Virus Decontaminating Agent: James B. Hudson , Manju Sharma & Selvarani Vimalanathan (2009)
    • Ozone Disinfection of SARS-Contaiminated Areas Kenneth K. K. LAM

    Cleaning and disinfecting frequently touched objects and surfaces are the recommended actions to help prevent the spread of respiratory diseases, like coronavirus. Since any surface can be re-contaminated after cleaning, and because the coronavirus is also spread person-to-person, Earth Blue Systems services are not guaranteed to prevent the future spread of coronavirus, but is able to eliminate 99% of viruses that are present at the time of treatment. Visit the Centers for Disease Control and Prevention

    (https://www.cdc.gov/coronavirus/2019-ncov/index.html) for more information regarding coronavirus, its spread, and prevention.

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