Which type of alarm is activated by larger, visible products of combustion?

The correct response involves understanding how different types of alarms respond to various indicators of fire. Photoelectric alarms are specifically designed to respond to larger, visible particles produced during combustion, such as those typically encountered in smoldering fires. These particles interfere with a light beam within the alarm, triggering it to activate.

In contrast, ionization alarms work based on a different mechanism; they are more sensitive to smaller smoke particles produced by flaming fires. Thermal alarms are triggered by changes in temperature rather than smoke, and smoke detectors can refer to either photoelectric or ionization types but are not specifically tied to larger particles alone. Therefore, the unique functionality of photoelectric alarms makes them the right choice for detecting larger smoke particles effectively.