The structure of the thermos flask is generally double-layered. The air in the interlayer is evacuated, and it is basically vacuum. The stopper is made of cork and other things, so it can play a role in insulation (preventing heat conduction, Convection, radiation).
There are several possibilities for the thermos not to keep warm:
1. The thermos flask has been used for a long time, and the insulation effect of the sandwich is poor.
2. The small pointed tip protruding from the bottom of the thermos is damaged, and there is air in the interlayer, causing no heat preservation.
3. The size of the bottle stopper is not suitable, and the hot gas leaks from the bottle mouth.
No matter what kind of situation causes no heat preservation, it is impossible to make the boiling water toxic, but the boiling water becomes cold, just like the boiling water in a large cup with a lid, it will never produce toxins, so you can rest assured, Drink boldly. I need to remind you: No matter whether the thermos is insulated or not, it is best to drink the water in the bottle within two days, and do not drink it on the third day. Because boiled water has been left for a long time, some minor changes will occur in the ingredients in it. Drinking it regularly is not good for the human body.