It is normal for cordierite stone which absorb oil and has something like cheese or sauce stuck on it creat smell under high temp baking, but you can see almost all the stone listings on Amazon have reviews complain about 'chemical smell' even the stone is whole new without any oil or anything stuck.
Cordierite stone is burnt on 2200F kiln which can burn off every harmful thing, seems not possible to has odor just under 600F baking.
I have think about this problem for some time, I am not possible to visit their house to see how terrible the odor is, also couldn't test with their stones in their ovens. I guess one possible reason is they were using new ovens or ovens never/ seldom bake with stone. Stone changes the heat airflow of oven, the metal inner shell of oven never/ seldom heated with very high temp for very long preheated time, so the metal diffuse some kind of chemical smell.
This is not baseless speculation. We have three ovens in our factory, I put stone on the top rack of the latest purchase oven last month, the stone blocked the hot air in a small place of the oven, so the hot air couldn't go down, the temp detector is in the middle of the oven where is much colder than the top, the oven keep heating up the stone with high temp for quite a long time, the stone almost reached 730F, the inner metal surface of oven even out of shape and became bent, the odor which may created by the coating of the oven inner shell is terrible.
Does your stone has an odor?
