What is the main difference in using a Heat detector or a Flame detector or Smoke detector? Thanks?

Question

Updated: So in which area should each of them be placed at? Is it advisable to place 3 of them in a room to have the best safety?

Answer 1

Heat detector - senses the change in temperature or rather rate of change in temperature.

Flame detector- Detects the flame by the radiation of the flame, emitted by it and also the rise in temperature.

Smoke detector- detects the smoke by chemically sensing the carbon dioxide and carbon monoxide contained in it.

Answer 2

A heat detector uses a thermometer to measure temperature rise. A flame detector uses an ionic emitter to detect molecule-sized particles emitted by a smokeless flame. A smoke detector uses a photocell and light source to detect the light-blocking character of smoke.

All three are important in detecting a fire, but most fire detectors now use the photoelectric method or a combination of photoelectric and ion emitter.

The problem with the flame detector is that while it will detect a smokeless flame, it will not detect a flameless smoke, such as what is created by a smoldering fire. Smoldering fires are often recursors to flame, so the smoke detector will give earlier warning.

Heat detectors do not provide an early warning, since the fire may be well underway before the sensor temp reaches the detection point.