Why do we need air disinfection?
The outbreak of new coronavirus (COVID19) worldwide has increased people awareness of the transmission of respiratory diseases in indoor environment. Evidences show that CORONAVIRUS could survive on respiratory droplets for up to several days and people breathing air containing these droplets will be at high risk to get the diseases. Therefore, there is a need for a reliable and efficient air disinfection method to decontaminate at home and high-risk areas.
Disinfection Methods by UV, HEPA Filter, Chemicals & Ozone
The most common air disinfection method is using ultraviolet (UV) radiation. UV radiation (UV-C) kills bacteria and viruses by damaging the DNA/RNA of the cells of microorganisms. However, UV radiation could only disinfect air close to the lamps as UV light has limited penetration capacity.
Another well-known air cleaning method is to use HEPA filter. HEPA filter can capture particulate sizes down to 0.3 microns, and so bacteria with size larger than 0.3 microns could be trapped in the filter, which is very effective in reducing airborne bacteria in air. But it’s useless to remove viruses.
Chemical disinfectants could also be useful for air disinfection, usually by means of spraying. However, these chemical disinfectants are generally difficult to decompose. It will leave toxic chemical residues that are hazardous to human health.
Ozone (O3) applications has been recognized as a safe disinfectant for water and food for many years now. It can be safely used in both gaseous and aqueous forms as an antimicrobial agent in the treatment, storage, and processing of foods, including meat and poultry. It is a very powerful disinfectant. Ozone could also be an effective air disinfectant. It can sharply kill 99.9% bacteria and viruses in air to purify the the room hygienically clean. As viruses are generally more susceptible to ozone than bacteria, it could assume that all viruses are killed if large percentage of airborne bacteria are removed.
Below is the disinfection efficiency of ozonation at different concentration in a room of 15㎡, which has been tested for 20 minutes. The results show that ozone is effective in reducing airborne bacteria.
Reduction of Airborne Bacteria after Ozonation
| Ozone conc. | 0,5ppm | 2,5ppm | 5ppm |
| Before Ozonation | 590 CFU/m³ | 615 CFU/m³ | 550 CFU/m³ |
| After Ozonation | 170 CFU/m³ | 40 CFU/m³ | 55 CFU/m³ |
| Reduction% | 71% | 93% | 90% |
However, for safety reason, excessive high concentration ozone should be avoided and the lowest ozone concentration that could kill most of the microorganisms should be selected as optimum. Depends on the contamination level, 0.5 – 2.5 ppm ozone level is adequate for air disinfection. Also kindly note that please stay away from the room when the ozone concentration is above 0,1ppm and return back after half an hour.
