[uuidgen]

I don't know about the US, but in the EU regulators DID step in and limited amount of ozone that can be produced by consumer devices to relatively safe levels. It will smell like thunderstorm but shouldn't be too toxic.

[bawolff]

According to wikipedia, california limits to 0.05 ppm and the more sensitive people start to smell it at 0.1ppm.

So if you can smell it, that's probably not great.

[uuidgen]

I don't think you can smell ozone - it's rather noxious. I think what you can smell as "thunderstorm" is the air cleaned a bit by ozone and the process of ionization (which traps some bigger particles).