Validation of a Low-Cost on-Demand Compact Ozone Covid-19 Sterilization Chamber

The COVID-19 pandemic has resulted in limited availability of N95 masks and other personal protective equipment (PPE). The sterilization and re-use of PPE can be of immediate benefit to help alleviate shortages and offer peace of mind to healthcare workers. Also, an inexpensive, precise, and portable sterilizer will have many applications beyond the current health crisis in a variety of field disaster relief operations. The sterilization of PPE and medical or other instruments will reduce costs, improve safety, and reduce waste. The portable sterilizer can also be utilized by individuals and businesses outside of the health care sector with similar benefits. Ozone sterilization does not require chemical consumables, uses ambient oxygen to generate ozone on site, and results in no toxic residuals. KWJ Engineering led the development of a small benchtop sterilizer with on board ozone generation controlled by feedback from an electrochemical sensor module and complete with an ozone destruct cycle for safety. Relative humidity as well as temperature and O3 concentration are also continuously recorded and can be maintained at the most effective levels for sterilization. Validation of the ozone sterilization protocol for deactivation of surrogate viruses on N95 masks has been demonstrated using TLS, an E. coli bacteriophage (bacteria-infecting virus), to provide a measure of effectiveness for variables such as time, ozone and viral concentrations, temperature, relative humidity, and virus-contaminated substrate. Additional organisms and conditions of sterilization are reported in this study to provide further analysis of efficacy of equipment and procedures as well as deleterious effects, if any, on PPE. The experiments with bacteriophage indicate that there is 99.99% inactivation of the robust bacteriophage when placed on N95 mask material with a one-hour treatment at 200 ppm ozone as compared to a 0-ppm control. The inactivation was shown to be 99.8% with only 50 ppm ozone. These ozone levels are easily achieved with a low power source and the entire system is operated using 12 VDC from a charger or battery. This sterilization effect is highly dependent on humidity, and the higher inactivation rates require higher relative humidity. The inactivation was demonstrated on multiple types of substrates with and without prior drying of the deposited phage. We expect the covid19 to be easier to inactivate than the bacteriophage and will test the system on SARS-CoV2 in a separate series of experiments. The sterilizer apparatus is simple and low cost and can be constructed from readily available parts and software for automated control is open sourced by KWJ.