After the work day is done and the janitorial staff has already done their job, have them set up the unit in the kitchen for the night. This will allow the ozone generator to run its course all throughout the night, without being disturbed. If there is a window in the kitchen, it would not hurt to crack it just a little bit for the night. In the morning, have whoever arrives first turn off the unit and put it away. However, if the smell is still lingering, let it run its course for another night.
You may need to do this a couple of nights per month, especially if you have a pub with foods that tend to leave a lingering odor.