That's a good question!! I'm so glad you asked!
It's best to take it slow and start off with body temp water. As you can tolerate the effects of the bath better, then you start building up both the water temp and the amount of time spent in the bath.
As an example - start off with body temp water and only stay in the bath for 7 - 10 minutes. Keep both of these the same until you are tolerating this well - maybe a couple of weeks??? Once you can tolerate that pretty well, then increase your water temp.
slightly and only stay in the water for 10 minutes. When you feel like you are tolerating that change well, then increase the amount of time in the water by just a few minutes - 12 - 14 minutes for example.
You will soon understand what I mean, as if you stay in the water too long or if your water temp is too hot, you will have an increase in symptoms - a herx. So pace yourself, each person is very different on this one as well.
The goal is to have the water quite warm - but careful to not get it too hot- and to stay in the water for a total of 20 - 30 minutes.
If, once you start the full detox baths, you find that you can't get started as you keep herxing, then switch to the foot soaks with Epsom salt and peroxide. They will do the same thing, only a bit slower. I still mainly use the detox foot baths as my detox pathways are still somewhat compromised, but I can keep up a regular detox routine without setting off herxes all the time.
If and when you start using the sauna, you'll need to be even more cautious, as they will also dehydrate you with the higher heat and all the sweating. When using the saunas (FIR or otherwise), a person needs to be pushing water consumption as hard as they can
while in the sauna as well as afterwards.