Most organizations recommend every year.
Realistically, you can go a couple years if you are just using it for basics.
If you are performing more advanced methods of ozone or need really specific concentrations then you should get it calibrated/analyzed every year.
Simply just send us an email at firstname.lastname@example.org or call an ozone specialist at (844) 655-2524 to get started.
Simply O3 customers get their first calibration free.