Another smoke detector question.

[bobrenwick]

I have heard there are two types of smoke detectors for residential. Some will not detect smoldered smoke, only smoke with flames.
This doesn?t sound right to me, but I don?t know. Any ideas or good sites to visit?

Also, should detectors be upgraded after so many years?

Thanks,
Bob

 

[mdshunk]

Read all about it:

"Are photoelectric smoke alarms better than ionization smoke alarms ...", from the Fire Safety Council

http://www.firesafetycouncil.com/pdf/review_on_best_sensor_type_for_kitchens.pdf

 

[wbalsam1]

I have heard there are two types of smoke detectors for residential. Some will not detect smoldered smoke, only smoke with flames.
This doesn?t sound right to me, but I don?t know. Any ideas or good sites to visit?

Also, should detectors be upgraded after so many years?

Thanks,
Bob

Types of Smoke Alarms:
IONIZATION: Contains a small amount of radioactivity that conducts electricity. Electric current flows continuously between two electrodes in the chamber. When smoke particles enter, they disturb the flow, causing the alarm to go off.
PHOTOELECTRIC: Contains a beam of light and a photocell within the chamber. When smoke enters, it deflects the beam, causing it to strike the photocell and set off the alarm.
IONIZATION VS. PHOTOELECTRIC: Ionization alarms are more sensitive to the tiny particles of combustion that can?t be seen or smelled, those emitted by flaming fires. Photoelectric alarms are more sensitive to the large particles of combustion emitted by smoldering fires. The differences between the two types are generally not critical, since the difference in response time is only a matter of seconds. Since most home fires produce a rich mixture of smoke types, with detectable amounts of both large-particle and small-particle smoke early in the fire?s growth, either an ionization or a photoelectric alarm will meet most needs.:smile:

 

[ZZZ]

smoke detectors

smoke detectors

I can't speak for residential applications, but when our facilities were upgraded to an energy management system that shut off air handlers over night and weekends we started having nuisnace fire alarms on a daily basis. We had Photoelectric duct detectors and when the fans would start around 5:00 a.m. the dust from the air filters and duct insulation would set them off. It was not a lot, you couldn't see it, but it was enough. When we finally found the cause, we changed them to the ionization type and never had another problem. We had a similar problem in high humidity areas, where the fog obscured the light beam. I think all smoke dectectors have a life expectancy, maybe 7 to 10 years I am guessing.

 

[kkwong]

ZZZ- You bring up a valid point for commercial facilities. Have you had any nuisance alarms since you changed? I have seen heats installed for that same purpose (to alleveiate nuisance alarms).

Bob- Are we talking about smoke alarms (local ennunciation only or an NFPA 72 detector)? For your question, I would say that there are dual type detectors out there (photoelectric and ionization) the only problem is price and finding them. I think Kiddie made one... As ZZZ stated, detectors (alarms) have a life of 7-10 years. Some of the alarms (detectors) have Americanium-123 (I think that is the isotope) which is radioactive. Some states have disposal policies dealing with them, but I doubt anyone enforces them. I think the ionization detectors have this isotope.

 

[bobrenwick]

smoke detectors

smoke detectors

Thanks for the help from all of you.

I'm talking about NFPA 72 types I believe. We use 120 volt with battery back up and interlinked. Residential. I had a friend whose detectors did not pick up a smoldering fire...at all. The smoke did alot of damage. From what I know now I'd have to say the detectors just failed, they probably were over 7 years old.

Which brings up another question....If one is adding one or two new smoke detectors to an interlinked system, do they have to be the same brand?

 

[mdshunk]

Which brings up another question....If one is adding one or two new smoke detectors to an interlinked system, do they have to be the same brand?

They should be, and even the same series. There was a time when the interconnect wire was 120V, but most now are 9V. There's no guarantee that replacing a few on a system that exists will even work as intended. They're all about the same age anyhow, so do them all.

 

[tallguy]

Which brings up another question....If one is adding one or two new smoke detectors to an interlinked system, do they have to be the same brand?

You'll likely find a stern warning in the instructions of the new ones you install that they are NOT approved/warranted/etc. for interconnection with other brands.

I have seen mixed brands working in apparent harmony -- but I wouldn't bet my life on it.

 

[bobrenwick]

Thanks for all your help.

 

[cbranter]

In your house I would change the detectors every 5 years or when you notice staining or excessive dust build up.
The cost is minimal and don't forget to change the battery operated ones at new years
Cheers