Which of the following best describes the function of smoke detectors?

Smoke detectors are specifically designed to identify the presence of smoke, which is a key indicator of fire. Their primary function involves detecting particles or gases produced by combustion. When smoke enters the detector, it triggers a response that activates an alarm, warning occupants of potential danger. This function is crucial for providing timely alerts that can help prevent injuries and save lives during a fire incident.

The other options refer to different functions that are not associated with smoke detectors. For example, detecting heat relates to heat detectors, while monitoring humidity and assessing air quality are functions of separate devices geared towards environmental control and health monitoring. Thus, the focus of smoke detectors on smoke detection is what makes the correct answer the best description of their function.