Sauna detoxes your skin, the largest organ of the body, the last resort the body has to release impurities.
Your stomach will be compromised first, accumulating more than 80% of the heavy metals in the faeces, that will not be evacuated by normal bowel movements, unless a colon cleanse is performed.
Then your liver pretty much at the same time as they are working together, so your liver will be so saturated in heavy metals that it will perform poorly
So your body will try to evacuate the heavy metals through your skin... The thing is that in modern life we don't sweat as much with our comfort ( Air Conditioning) and machines doing things for us ( cars, computers, vacuum cleaners, ...).
So you need a good sweat that a sauna will do well. Drink a lot of water and don't overdo it.
In the beginning of your detox try a sauna every day, then little by little space them out.