O3 isn't harmful in small quantity : https://en.wikipedia.org/wiki/Ozone#Consumers

Also, ozone purifiers not need to keep working all the time. A usual usage it's have a burst of ozone to sanitize a place, and wait a few minutes to decompose to O2. The result is that any smell is removed, and the ambient is sanitized. I saw this a lot on hotels where they use "ozone cannons" where they are cleaning rooms.

It also smells bad too

That's very subjective - I quite like the smell.