Fermentation is probably older than civilization and agriculture. It is a perfectly safe hobby that does not produce any poison or foul smell. When it comes to the safety aspect, follow the 4 golden rules:
- If the smell is funky, then it is better to discard
- If you see mold or a white-green-black floating film on top then discard
- If you are not distilling or fermenting wood or other inedible substances then one need not worry about methanol
- If the tastes are odd, then discard. Better safe than sorry.
People have been fermenting beer, wines, and ciders for 5 thousand years across the globe with various simple crude setup. A modern kitchen is much more hygienic and hi-tech than the early man’s setup. So if one could do a safe fermentation in a crude setup, then they can do the same in a modern kitchen. So be assured that if a recipe is followed, then a home brew will not make you sick or poison you.