Ozone, especially if generated and used for treatments within an indoor environment, can take anywhere between 48-96 hours for its residual smell to be removed. In some cases, it can remain for up to a week!
Factors such as the square footage of the treated area, amount of time ozone was deployed for, the number of retentive materials within the space (i.e., carpets, textiles, etc.) and the quality of ventilation will all play a part in getting rid of the ozone smell.
The biggest help in getting rid of ozone odors can be summarized with:
Dilution is the solution to pollution.
A proper exchange of air and a well-ventilated indoor environment is your best friend when getting rid of ozone smells by diluting the concentration of ozone odors. HEPA air scrubbers or negative air pressure is often used to help facilitate this process, especially in areas with heavy ozone applications.