Both sensors can be used for fire alarm alerts. The "Smoke & Heat" detector gives more peace of mind, since it recognizes not only smoke, but also a high temperature (>57 Celsius or 135F). However this sensor is not suitable for use in premises where a high temperature is normal. If you install the "Smoke & Heat" sensor in premises of this nature, it may send false alarms. For such conditions the "Smoke" detector would be the best.