For insufflation I have always used an oxygen feed, at that time they said that was the only way to go, I thought even for a cold corona.
Technically yes since this is the only way to really know what the ozone concentration is. But not everyone has access to 100% pure oxygen. And if someone has a serious condition, such as advanced cancer, the benefits of using a cold corona ozone generator with an oxygen concentrator still outweighs any potential problems.