NFPA72 - Smoke Detector vs Smoke Alarm

[Leo]

Smoke Detector vs Smoke Alarm

a Smoke Detector and Smoke Alarm are not the same thing in NFPA72
Smoke Detector - control set
Smoke Alarm - houses

3.3.180 Smoke Alarm. - A single or multiple station alarm responsive to smoke. (SIG-HOU)
Smoke Alarms are usually for homes, and have the sounder built in, also are power via 110vac with batteries and can be interconnected so all the smoke alarms with sound if one goes off.


3.3.181 Smoke Detection.
3.3.181.1 Cloud Chamber Smoke Detection. The principle of using an air sample drawn from the protected area into a high-humidity chamber combined with a lowering of chamber pressure to create an environment in which the resultant moisture in the air condenses on any smoke particles present, forming a cloud. The cloud density is measured by a photoelectric principle. The density signal is processed and used to convey an alarm condition when it meets preset criteria. (SIG-IDS)

3.3.181.2* Ionization Smoke Detection. The principle of using a small amount of radioactive material to ionize the air between two differentially charged electrodes to sense the presence of smoke particles. Smoke particles entering the ionization volume decrease the conductance of the air by reducing ion mobility. The reduced conductance signal is processed and used to convey an alarm condition when it meets preset criteria. (SIG-IDS)

3.3.181.3* Photoelectric Light Obscuration Smoke Detection. The principle of using a light source and a photosensitive sensor onto which the principal portion of the source emissions is focused. When smoke particles enter the light path, some of the light is scattered and some is absorbed, thereby reducing the light reaching the receiving sensor. The light reduction signal is processed and used to convey an alarm condition when it meets preset criteria. (SIG-IDS)

3.3.181.4* Photoelectric Light-Scattering Smoke Detection. The principle of using a light source and a photosensitive sensor arranged so that the rays from the light source do not normally fall onto the photosensitive sensor. When smoke particles enter the light path, some of the light is scattered by reflection and refraction onto the sensor. The light signal is processed and used to convey an alarm condition when it meets preset criteria. (SIG-IDS)

[peermoh80]

Mr.Leo,

clause 29.8.4.4 NFPA 2010 "In rooms with open joists or beams, all ceiling-mounted detectors or alarms shall be
located on the bottom of such joists or beams."

is above clause applicable for spot type smoke detector?

[peermoh80]

Hi all,
anybody have answer for my question.

[Leo]

I am trying to answer your question but I keep think of different scenarios which changes my answer.
The best thing to do is pay the $200 for a NFPA membership and call them. it will be the best $200 you spend.

[pyrosucks]

29.8.3.4 references section 17.7.3.2.4 for locations of spot detectors in rooms with joists or beams.