Many people utilize the terms smoke detector and smoke alarm to describe the same device. The terms are actually not interchangeable. A smoke alarm describes a device that detects smoke vs a device that detects the presence of certain gases or heat. Smoke alarms will utilize a horn or audible alarm within each unit and can be interconnected to provide an alarm through an entire residence. A smoke detector utilizes detection devices that are connected to a central alarm panel.
The information for this answer was found on our Carbon Monoxide & Smoke Detector Laws answers.