If one of the rings on your parents' Bosch gas stove has been burned by fire, there is a possibility that it could emit dangerous chemicals when used again. The extent of the danger would depend on various factors, such as the materials used in the construction of the stove, the severity of the fire damage, and the specific chemicals involved.
When a gas stove is exposed to high temperatures, the materials it is made of may undergo changes that can release harmful substances when heated later on. For example, if the burner's enamel coating or any plastic components have melted or burned, they could potentially emit toxic fumes when the stove is used again.
To ensure safety, it is essential to have the stove thoroughly inspected and repaired by a qualified technician before using it again. A professional can assess the damage and determine if any parts need to be replaced or if it's safe to continue using the stove.
In the meantime, avoid using the affected burner until it has been properly assessed and repaired. Additionally, make sure the kitchen is well-ventilated when using the stove, as this can help minimize the potential health risks if any harmful substances are present.
It's always best to err on the side of caution when dealing with potential safety hazards, so don't hesitate to seek expert assistance to ensure your parents' stove is safe to use.