1) When inhaling?
Any time Brown’s Gas is inside your body, you want to make sure the concentration within your lungs never reaches or exceeds 4.7%, at which point it becomes explosive.
In the manual, there’s a chart which will help you determine at which duty percentage to run the AquaCure. That percentage is based on your body weight — 20% of your weight — to ensure that the concentration of gas in your lungs remains at 2%. This is enough to saturate your body with hydrogen within 20 minutes while keeping you safe.
2) For external applications?
For strictly external use (i.e., bubbling water without inhaling at the same time, using the spot applicator, etc.), you can set the duty percentage to 100%.