The amount of NoX produced does not matter much if you're doing short term ozonation projects like ozonating water or lightly ozonating oil. The benefits of the ozone produced far outweigh the potentially negative effects of the NoX. However, if you plan to try to fully ozonate oils with an air fed machine, the amount of NoX build up in the oil over the time required to produce the oil can be quite harmful to mucous membranes. This is especially true in humid climates since the amount of NoX produced by a corona field is in direct proportion to the amount of humidity in the room air feed gas.
Hope this helps