Hi Gisela,
On the Portazone website (" Hulda Clark ozonator" will bring it up too), they suggest running the ozonator in the water for 15 minutes. I have run it for upwards of 20 minutes. You may smell some ozone rising above the water, but it should be a small enough amount not to bother you.
How do you like the wz04? How much does it weight? Would it be easy to travel with?
I look forward to hearing how you like the ozonated water. I usually start my day with 16 oz., to get the body kicking.