What type of detectors employ more than one operating principle and operate independently?

Combination detectors are devices that integrate multiple detection methods into a single unit, allowing them to operate independently yet work together to enhance fire detection capabilities. These detectors are designed to utilize more than one operational principle, such as heat detection, smoke detection, or gas detection, providing a broader range of response to different types of fire conditions.

By employing multiple principles, combination detectors improve the likelihood of early fire detection, as they can respond to various fire characteristics that may not be effectively identified by a single type of detector. This versatility is especially useful in complex environments where different fire hazards may exist.

In contrast, multi-criteria detectors also utilize multiple detection methods but are more integrated in terms of processing and analysis, often relying on sophisticated algorithms to determine the presence of a fire. Napkin detectors do not exist in fire safety terminology, and thermal detectors solely focus on heat detection without employing additional principles. Hence, combination detectors stand out for their independent operation and dual approach to fire detection.