The National Fire Protection Association (NFPA) reports that there is a fire death in the US every three hours and thattwo-thirds of household fire deaths occur in homes with no or with malfunctioning smoke alarms (www.nfpa.org/research). Protecting property and lives from damages and losses due to fire is clearly one of the most basic and important safety measures one can take and fire alarm devices are a reliable first line of defense.
There are two types of fire alarm devices:Heat Sensors and Smoke Sensors. This article aims to address any confusion on the two by shedding light on the working principles of each and investigating their similarities and dissimilarities.
A HEAT SENSORsenses changes in temperatureresulting from combustion and is triggered when there is a rise in temperature above a set level. It utilizes electro-pneumatic technology and gets activated when:
– A predetermined fixed temperature is reached (the standard trigger point is 135 degrees F);
– A rapid increase in temperature has occurred. The sensor can determine when there is an unusual rate of rise in the room temperature, typically increasing by more than 15 degrees F within a 60-second period.
A SMOKE DETECTOR or SMOKE ALARM is a device that senses smoke as an indicator of fire.
1) Ionization smoke detectors have a chamber with two plates that generate an electric current. Any smoke that enters the chamber attaches to the ions, interrupts the current then sets off the alarm. Ionization type detectors respond quickly to flaming fires.
2) Photoelectric smoke alarms use a light beam. When smoke interrupts the beam, the alarm is activated. Photoelectric detectors are highly-responsive to long, smoldering flames.
3) Combination smoke alarms which employ both ionization and photoelectric technologiesoffer wider coverage and are therefore recommended for use by the NFPA.
HEAT SENSORS AND SMOKE SENSORS: SIMILARITIES AND DIFFERENCES
Both heat and smoke sensorsdetect fire. They prevent potentially catastrophic consequences to property and liveswhich can result from this.
Simply put, the basic difference between the two is that heat detectors detect heat, smoke detectors detect smoke. Their operating principles are different — heat detectors sense elevations in temperature and they go off to indicate potential fire while smoke detectors sense the incidence of smoke. They are not interchangeable; one does not perform the function of the other. A heat detector will not go off in the presence of smoke and a smoke detector will not be triggered with a rise in temperature.
Because many fires begin with billowing smoke before intense heat ensues, smoke alarms can get activatedbefore heat detectors go off. Smoke sensors are triggered even with a small amount of smoke, making them more sensitive than heat sensors but also more prone to false alarms. Nevertheless, the more important thing to noteis that smoke alarms give earlier, more advanced warning of fire than heat sensors which can prove crucial in escaping a life-threatening fire situation. Smoke alarms are therefore well-covered by building codes and laws in many states and are a more common fixture in homes.
Used together, heat and smoke detectors provide extra warning of and comprehensive protection from fire incidence. It is ideal to have both installed in the home and this dual set up is not uncommon. Smoke sensors, though, take higher importance of the two because of their capability to give earlier warning of fire.
The good news to homeowners is that there are already home security system companies which offer combined smoke and heat sensors in a single device. “A Frontpoint Smoke and Heat Sensor not only detects smoke, it can detect when a room is getting too hot, too fast.” (www.frontpoint.com)
As a final safety note, integrating fire monitoring to one’s home alarm system gives even more thorough protection in the event of fire. This quickly summons emergency services even when the homeowner/ other household members are away; or even when they are at home or in case younger or elderly family members are home alone — and are overwhelmed by the smoke and intense heat.