Chlorine dioxide is very powerful. It need to be handled very carefully, and precautions need to be taken while handling it.
The last time I was involved in a chlorine dioxide incident, the people passing through the area reported the problem before the monitoring alarms sounded. They recognized that there was a problem because they suffered adverse effects from their very brief exposure.
You ask about a therapeutic dose. A study in Japan revealed that a concentration of 0.01 PPM was effective in preventing the spread of viruses in the air between animals. In contrast, the odor detection concentration for most people is about 0.1 PPM. The general rule is that if you can smell it (which is stronger than simply detecting it) you are in danger of suffering adverse effects and should get out of the area.