A device which detects the visible particles of combustion is a ____ detector.

The correct answer is smoke detector, as smoke detectors are specifically designed to detect the visible particles that are produced during combustion. When materials burn, they release smoke that contains these particles, and the smoke detector uses various technologies, such as photoelectric or ionization, to sense the presence of these particles in the air.

Smoke detectors play a critical role in fire safety by providing early warning of fire, allowing occupants more time to react and evacuate. Their effectiveness is largely attributed to their ability to recognize the byproducts of combustion, which are crucial for identifying a fire before it reaches an advanced stage.

In contrast, heat detectors respond to thermal energy, flame detectors are designed to perceive the light emitted by flames rather than smoke, and gas detectors primarily focus on identifying specific gas concentrations in the air, rather than detecting visible particulates. Each type of detector has its specific application and function within fire safety systems, but for the detection of visible combustion particles, the smoke detector is the appropriate choice.