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
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.