What type of thermometer cannot be used without a shatterproof casing?

A glass thermometer cannot be used without shatterproof casing because it contains mercury or another liquid that can be hazardous if the glass breaks. The glass tube is fragile, and the risk of it shattering poses safety concerns in a food handling environment where food safety and employee safety are paramount.

In settings such as a Starbucks store, where the workplace must maintain high safety standards, using a glass thermometer without shatterproof casing would not only risk contamination but could also result in injury. The other types of thermometers listed are designed for durability and safety in busy environments, which makes them preferable for food handling and service.