[HH] Spam (7.632):Re: Smoke detectors self-destruct

[Federico Lucifredi]

Hello Ethan,

> On Apr 13, 2017, at 7:24 AM, Ethan Schwartz <ethan.boston at gmail.com> wrote:
> 
> 
>> On Apr 12, 2017, at 11:53 AM, Greg Rundlett (freephile) <greg at freephile.com> wrote:
>> 
>> I bought a house 6 years ago, and I was perplexed this week as ALL the First Alert combo smoke + CO detectors started chirping and went bad.
>> 
>> The First Alert smoke detectors have and "End of Life" feature that: [1]
> 
> I don't think this is sinister or planned obsolescence--
> 
> All CO sensor types have finite lifespans, after that point they may not alert to dangerous levels of CO.  

On the technical level, you are 100% correct, and I have to agree with you. Until someone sells me a CO sensor that does not decay (and the economic incentives are against it right now), anyway.

I know that besides NDIR (gas-filled tube IR-illuminated, filter window blocks light frequencies not relevant to CO, measure light level) there are biomimetic (a gel changes color, the color change is detected), Metal-Oxyde Semiconductor (change in resistance, circuit detects), and electrochemical (electrodes in a chemical bath) variants of CO sensors. These decaying home versions… I could not find out which they are. Does anyone know?

My hunch is they are chemical bath versions, and that the chemical reaction only goes so far in reverting (chemistry is pesky that way). I also found a teardown of a detector model confirming this: http://www.robotroom.com/Inside-Carbon-Monoxide-Detector.html

Conversely, does anyone know of a home CO) sensor without expiration (don’t need it that bad, but it would point to the tech inside!). First Alert and Nest are 10-year service life. I see decaying lifespans even on furnace (inside - NDIR) and combustion engine (injection computer - NDIR) sensors as well, so this is hardly unusual.

> 
> This end of life feature is to prevent people from installing them and never replacing them as long as they don't chirp.
> 
> A well rated combination detector costs between $25-50.  Even if you have a dozen in your home that's $300-600 every 5-6 years.  As far as home maintenance costs and effort goes this is not very high, you should probably be replacing or servicing fire extinguishers around the same timeframe too.

On the business level, I do not agree: these detectors cost $25-50 because they have a government-guaranteed demand curve, and vendors are just waiting for the money to come in. While the government clearly has good reasons here, the combination of that with limited competition gives you… pricey sensors. I could be paying $50 for all sort of parts of my house that come for $4.50 today… like my basement flood sensor, which folks have to sell to me without a government mandated demand. I hope we get there soon for these as well, I see no reason for something produced in the tens of millions to be this pricey — It is not an iPhone!

> 
> If you have gas appliances in your basement I'd have an explosive gas alarm down there too.

Now this is actually interesting. I have all of the above already but not the explosive gas alarm (I am a sensor guy, I get these even when I don’t need them to learn more about them), do you have a model you use/recommend?

Thanks for sharing!

Best -F

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_________________________________________
-- "'Problem' is a bleak word for challenge" - Richard Fish
(Federico L. Lucifredi) - flucifredi at acm.org - GnuPG 0x4A73884C