Ozone (O3) is an unstable gas comprising three atoms of oxygen. It is unstable because the gas will readily degrade back to its stable state diatomic oxygen (O2) with the formation of free oxygen atoms or free radicals. The free oxygen atoms or radicals are highly reactive and they will oxidize almost anything (including viruses bacteria organic and inorganic compounds) in contacts making ozone an enormously powerful disinfectant and oxidizer.

 
In fact ozone is a much stronger oxidizer than other common disinfectants such as chlorine and hypochlorite. The usage of chlorine or hypochlorite in many countries has been decreased significantly due to the possibility formation of carcinogenic by-products such as trihalomethanes (THM) during the disinfection process. In contrast ozone disinfection does not produce any harmful residues and all the residual ozone will be converted back to oxygen within a short time. Ozone is therefore considered as an environmentally friendly disinfectant.

Ozone for air purification also do odor deodorization and bacterial sterilization.
In so doing the air is naturally fresher because the source of the odor has been destroyed.

Ozone acts directly on the cellular walls of the microorganisms. It oxidizes organic matter in bacterial membranes which in turn weakens the cell wall and leads to the cell rupture. The internal cellular material/plasma is released into the external environment which causes immediate death of the cell.

In contrast other oxidizing and non-oxidizing biocides must be transported across the cellular membrane where they act on the nuclear reproductive mechanism or on enzymes essential for the various cell metabolisms. Such mechanism of disinfection is not as rapid and efficient as ozone since these biocides need to be used in higher concentrations or much longer contact times.

During commercial applications however the disinfection process should also be viewed in terms of the exposure to materials that will come in contact with ozone. It is recommended that those materials be used which are compatible with ozone at the concentration levels used in the disinfection process.

Some of the applications of ozone for air treatment are as follow:
Ventilation and air-conditioning system for air disinfection odour control and improved indoor air quality in various building premises.
Kitchen and food odour control ? Cigarette odour control in bars and restaurants.
Sewage odour control in pump stations.
Rubbish bin centre odour (volatile organic compounds) control.
Toilet odour control.
Cold room air treatment for microbial control odour control and extension of shelf life of fresh produce.

However odour control using ozone is often achieved due to the oxidation of volatile organic compounds – VOCs – or inorganic substances.

For safety reason 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 a hour after ozonation therefore people should wait for at least one hour (after turning off the generator) before entering the “ozonated” room.