What type of device is commonly used to detect smoke in a building?

A smoke detector is specifically designed to identify the presence of smoke, which is typically a result of combustion. It works by using various technologies, such as photoelectric sensors that detect smoke particles or ionization sensors that react to changes in air caused by smoke. This makes it an essential safety device in buildings, as it provides early warning in the event of a fire, allowing occupants time to evacuate and alert emergency services.

The other devices listed serve different functions. A thermistor primarily measures temperature and is used in applications where temperature control or monitoring is critical. A CO2 sensor detects carbon dioxide levels, which is useful for assessing air quality and ensuring adequate ventilation but does not provide information about smoke. A pressure switch is designed to detect changes in pressure within a system, which is not related to smoke detection. Hence, the smoke detector is the most appropriate choice for identifying smoke in a building.