Photoelectric smoke detectors detect smoke, but not all fires produce it. Ionization smoke detectors detect by products of combustion, but they can be prone to false alarming. Heat detectors, on the other hand, spot temperature changes, but these aren't always an indicator of a life-threatening event. Multisensor devices, however, collect data on several different environmental parameters at the same time, and then weigh the results to determine whether an alarm should be sent to control panel.