Final answer:
Glass thermometers should only be used with food when there is no breakage risk, although digital or dial thermometers are generally preferred due to their durability and ease of use.
Step-by-step explanation:
The only time glass thermometers should be used with food items is when there is no risk of the thermometer breaking and contaminating the food. In professional and home cooking environments, it is advised to use thermometers made from more durable materials that can withstand being dropped or subjected to sudden changes in temperature. Glass thermometers might still be used in situations where they are protected and unlikely to break, such as when inserted into large cuts of meat in an oven. However, they are generally not recommended because if they break, they can cause physical hazards by leaving behind glass shards and chemical hazards if they contain substances like mercury.
For food safety, it is crucial to ensure that food reaches a high enough temperature to kill any bacteria it may contain. Modern digital or dial thermometers are often preferred for their durability and ease of use. Yet, glass thermometers that are specifically designed for culinary purposes and do not contain toxic substances can be used cautiously.