People traveling around the world have resulted in the rapid spread of emerging viruses and other diseases. If a disease becomes prevalent in a particular city, it can quickly spread internationally due to travel of the originating city's inhabitants. Once the disease is identified and infected individuals isolated, the disease has often already spread to high-density municipal areas, potentially in other countries, where it can be very difficult to control.
An example of such a disease is found in the rapid spread of Severe Acute Respiratory Syndrome (SARS), which has a high mortality rate and can be difficult to treat. It is also very difficult to screen infected people and prevent them from spreading the disease. In particular, the spread of such diseases poses a high risk to the hospitality industry, and can lead to reduced earnings and share prices of public companies in the hospitality sector. The aggressive spread of SARS from Asia to other countries including the United States and Canada has challenged the airline, hospitality and tourism industries as well as hospitals. The spread of SARS also had a negative impact on affected countries' economies, including that of major cities such as Toronto.
SARS is not the only virus of concern. A variety of airborne, gastro enteric and enteric viruses, including varicella zoster (chicken pox), measles virus, rhinovirus (cold), influenza virus (flu), poliovirus, rotavirus, hepatitis A, norovirus, adenovirus, and emerging viruses all represent risks of contagion and infection. The spread of bacterial infections and fungus can also be of significant concern, particularly when drug-resistant varieties of bacteria occur.
Such diseases are also of concern in the health care sector. For example, clostridium difficile (a human pathogenic bacterium of the intestine) is very difficult to remove when infected individuals are kept at a hospital. Health care workers and future patients may be put at risk in such situations.
Ozone has long been recognized as an effective biocide (a biochemical disinfectant) in aqueous form, and is also a powerful deodorizer in a gaseous form, having a number of attractive features. For example, gaseous ozone is pervasive in a closed space. Ozone is also highly effective as a viricide, and is inexpensive to administer, as ozone generators are plentiful and easy to install and operate.
Ozone is naturally formed, particularly in the upper atmosphere, when high-energy ultraviolet rays sever conventional oxygen (O2) bonds, creating free radical oxygen atoms, which then react with other O2 molecules to form ozone (O3). Ozone is also formed naturally such as during lightning storms, at ocean beaches, and waterfalls.
The structure of ozone is highly reactive, and consequently ozone has a short half-life (about 30 minutes). When ozone breaks down, it produces oxygen and a free radical oxygen atom. This oxygen free radical is a powerful oxidant.
There are several ozone generators described in the prior art. For example, U.S. Pat. No. 5,904,901 to Shimono discloses a deodorization/odor-removal/disinfection method and deodorization/odor-removal/disinfection apparatus.
Prior art relating to the sterilization of hotel rooms and the like using ozone includes JP4038957A2, which discloses a determination of the time a room should be exposed to a particular concentration of ozone. JP2237565A2 discloses an indoor sterilizing method, which includes placing an ozone generator in a room, generating a level of ozone, leaving the ozone at that level for a period of time, and then decomposing the ozone.
Another prior art ozone generator is disclosed in US Patent Application Pub. No. 2005/0031486 to Mole et al., entitled “Sterilization and Decontamination”. Mole et al. discloses an ozone generator that generates ozone after the humidity in the environment has reached at least 75%. The ozone generator then raises the ozone level to 10 ppm, allows a certain amount of time to pass, and then releases hydrocarbons to a concentration up to 20 ppm until the ozone level is depleted.
What is missing in the prior art is a timely way of delivering ozone to a closed environment, using other factors to minimize the time necessary for the ozone to carry out its purpose, and efficiently removing the ozone from the environment.