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I've viewed dozens of "top X smoke detectors of 2020" sites, and scoured the leading brands' sites (Kidde, First Alert, and Nest), but I can't find any that are battery operated, dual sensor (ionization and photoelectric), and interconnected (wirelessly). I can't install hardwired detectors in my home due to lack of access inside walls and ceilings. Many resources say dual sensor is recommended because they cover both smouldering and fast flaming fires. Additionally, it's now law that all new homes have to have interconnected alarms so a fire detected in a distant part of the house will be heard, which is a concern I have even though I don't own a new home. So why don't they exist with those three?

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  • Is[ this one](amazon.com/…) good or is it not dual sensor? It is wirelessly, battery powered, detects smoke heat CO etc...
    – Kris
    Dec 27 '20 at 2:13
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    Keep in mind that there's been some innovation in photoelectric smoke detection (using dual wavelengths to discriminate between particle types), in addition to updates to the UL 217 testing standard (where they now burn standardized hamburgers in an oven, make sure none of the smoke-alarms-under-test go off from the burger smoke, and then proceed to light a test PU cushion on fire and make sure the smoke-alarms-under-test do go off within a set time after the cushion is ignited), that make dual-sensor technology no longer as much of a requirement for nuisance smoke rejection as it used to be Dec 27 '20 at 2:14
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No Demand

The demand for interconnected is associated with new homes in many jurisdictions. I don't know of any places (there may be exceptions, probably California if anywhere...) where they are required to be interconnected unless a home is new or, possibly, substantially renovated. When a home is new or is substantially renovated, it is easy to run wires between the detectors and to add wires from the first detector back to a power source.

So the need for "battery" is made obsolete by the need for "interconnected". You don't need battery if they are interconnected, you don't need interconnected if you are in a situation where you don't want to run wires back to a power source (because if you don't want to connect to power, you probably don't really want to run wires for interconnecting them either).

End result:

  • Battery power for individual detectors in older homes. (Unrelated, but now typically "10-year batteries" instead of "replace battery when you hear the chirp").
  • AC-powered for interconnected detectors in newer homes.

I don't think dual-sensor has much to do with it, though due to power requirements (and possibly a higher price-point) that may be more common with AC-powered, interconnected detectors.

I didn't catch the "wireless" part originally. For a bunch of reasons, I would prefer wired to wireless for smoke detectors. Wireless at many levels (from Bluetooth to WiFi to cell phones...) has enough problems that for life-safety I'd prefer wired, when practical. As long as this is new construction, wired seems quite practical, and new construction is the primary demand source for interconnected.

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  • Look, the point is "interconnected" means when one goes off they all go off, not that they're hardwired. If an alarm goes off in the basement and our bedroom is on the third floor with white noise machine on, we want to hear the alarm, so we want the one in our bedroom to go off too. You didn't say anything worthwhile about dual sensor either, despite the NFPA recommending them "for the best protection [from fires]".
    – rory.ap
    Dec 28 '20 at 1:17
  • Also, and more importantly, you didn't even try to answer the actual question: "Is there a technical reason why there are seemingly no smoke detectors that are battery operated, dual sensor, and interconnected?"
    – rory.ap
    Dec 28 '20 at 1:28
  • My point is that it is not a technical reason - a company could make such a thing if they wanted to. But for bulk consumer products (and smoke detectors in for anything < $ 100 each are "bulk consumer products"), mass market rules. Mass market is for (a) single detector photodetector currently due to laws in several states (whether the laws make sense or not is immaterial, companies want to sell one product line nationwide) and for either battery powered (simple replacement of existing detectors) or wired/AC-powered (new construction). Market driven, not technical. Dec 28 '20 at 2:12
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Vermont actually requires photoelectric-ONLY and CO. (Yeah, sure, you may not be in Vermont.) But the stated reasoning for the law being that way is "outdated ionization type alarms" so you may be applying outdated logic to alarm selection. I found it a bit surprising myself when I noticed that language in the requirements. You might want to check the details of the rules that apply to your area... (Three Phase Eel's comment seems to shed some light on what may be up with that.)

In any case, I found none of the "usual run of home center consumer alarms" (what you call "leading brands" - which they are not, if you include the much larger market of dedicated alarm system manufacturers) suited me, so I'm installing a "central" type with one rechargeable backup battery and a clear indication of which head went off, rather than going through the utter [expletive] of individually AC powered, individually disposable battery backed-up, interconnected but not at all clear where the alarm was actually coming from crud that seems to be what's on offer at home centers. Those make false alarms incredibly annoying (run around in the din trying to find which head has a light on.)

I'm hardwiring, but there are wireless versions of those, too (which I don't particularly trust with life-safety as a person who does wireless professionally, plus I am building the wiring into the building, not trying to add it to a finished building. But there are ways to do that...)

If you want a "smoke and dust insensitive" detector that still responds to fires, heat detectors are available (and inexpensive.) Combination smoke and heat detectors are also available.

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    I have to wonder if the Vermont "no ionization" is based on an overreaction to the incredibly tiny bit of radioactive material inside an ionization detector. Because if it is about detection capability then it shouldn't matter if it is photoelectric, ionization or a bunch of tiny elves with sensitive noses (no offense to the elves). Dec 27 '20 at 3:13
  • I've noticed that I don't see ionization detectors when I'm shopping central alarm smoke detectors, either. So I doubt that's it...
    – Ecnerwal
    Dec 27 '20 at 3:20
  • @Ecnerwal -- yeah, ionization detectors have been largely phased out of central alarm use, probably partly due to disposal concerns and partly due to their poor..."tunability" compared to photoelectric (esp. modern multi-wavelength) detectors Dec 27 '20 at 3:24
  • A quick search finds some reference (on lawyer sites...) to ionization being slower reacting. But NFPA says both are good and ionization faster for certain types of fires. I have a feeling (but can't prove it) that the reality is a mix of misinformation and stupidity. If the issue is speed of reacting/alarming, then make specific requirements "alarm within 'x' seconds to 'y' standard test fire". Imagine if CFLs were mandated in such a way that LEDs were technically prohibited (I could see ways to write such a regulation) and then a better technology would get pushed aside. Dec 27 '20 at 3:25
  • I'm not saying ionization is a better technology than photoelectric, but write the regulations based on the desired outcome and not based on "current technology". Annoys me in many other realms as well, especially a lot of regulations that have been added (and removed and updated...repeatedly) in the past 9 months or so... Dec 27 '20 at 3:26

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