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Comment by jeanjq | Hacker News Reader

What is wrong with the $7.50 Kidde?

http://www.amazon.com/Kidde-Sentry-Battery-Operated-Ionizati...

Reviews seem good.

We have this exact brand in our apartment. They (like almost all ionization-based smoke detectors) go off at the drop of a hat. And they're ear-splittingly loud. The kill switch is hard to press, and needs to be pressed every few minutes if you're, say, burning incense. And one day, when the battery gets low, they'll start chirping in the middle of the night, leading to a game of "Which one is it?!" as they somehow manage to make noise frequently enough to prevent sleep but infrequently enough to thwart identification of the dying one.

(Smoke detectors' low battery alerts always go off at night because battery output sags when the temperature goes down.)

A smoke alarm being very loud and very sensitive is a feature to me, not a bug - I'd rather be annoyed from time to time than die of smoke inhalation in my sleep. As for 'hunt the low battery' - how many smoke alarms do you need in one area?

False dichotomy. With an extra ten cents' worth of technology, the smoke detector could do its initial chirping quietly and during daylight hours. If you ignore them, then later it can escalate to around-the-clock 85-decibel alerts.

Ditto sensitivity. At the first wisps of a problem, give a gentle sound. If it gets worse, or 60 seconds pass, then get shrill.

Re: "how many do you need in one area?" the last three words do not apply. The low-battery chirp is loud enough that a dying battery anywhere in the house can wake you up. For the record, though, we were required to put one in every bedroom and two in our small hallway -- and that's just on our upper level.

Have you seen how quickly an actual house fire takes hold? There are videos of fire department demonstrations on YouTube (http://www.youtube.com/watch?v=rUh4rCjuYDA for example). In sixty (or even ten) seconds of gentle sounds, you'd probably be dead. Not to mention that smoke can take time to rise up to smoke detector level - crucial seconds that you could be using to escape rather than comfortably waking up.

As for the low battery chirp, it should be annoying - that way you attend to it rather than leaving it until later. And chirping only during the daylight hours - how is that helpful if you're out at work? The battery will be dead before you even know about it.

Smoke alarms should be intrusive when they need your attention. That's how they save lives.

P.S. as for the last point - I was actually referring to how difficult it is to work out which smoke detector is chirping. Thus my question - I can't see how it's difficult unless you have lots of smoke alarms. Badly explained on my part, sorry.

> In sixty (or even ten) seconds of gentle sounds, you'd probably be dead.

Which is why I also said that, if the problem gets worse that just a few wisps, the detector should immediately escalate to full alarm.

> And chirping only during the daylight hours - how is that helpful if you're out at work? The battery will be dead before you even know about it.

Again, it can start quiet and polite, and then escalate to more aggressive notifications if you ignore it.

> Which is why I also said that, if the problem gets worse that just a few wisps, the detector should immediately escalate to full alarm.

Indeed, but personally I don't want a dumb electronic device to make that judgement for me - I'd like to do it myself. I'll know instantly whether or not the house is on fire and I'd like to know instantly whether or not it seems like it might be. False positives are, as I said earlier, infinitely preferable to "he'd have made it out if he'd heard the alarm earlier". Besides, how do you decide what's "house fire smoke" vs "burnt toast smoke"? if the fire isn't adjacent to the detector then smoke may only reach the detector slowly.

I get the drive to make devices more intelligent and thus more convenient but I strongly disagree that this philosophy should apply in all cases. Sometimes 'basic' really is better. Not to mention that there's less to go wrong.

> Indeed, but personally I don't want a dumb electronic device to make that judgement for me

But ultimately, you have no choice. Even the ideal smoke detector that you have in mind is going to be a dumb electronic device that has to make a judgement for you.

It'll have some sort of threshold before the loud alarm goes off. I'm not suggesting that be changed.

What I'm suggesting is that, in addition to that, at an even more sensitive threshold, there be a quieter alarm, too.

Usually smoke detectors are a 1 in each room (and 1 in the main hallway) thing nowadays.

And as for the hunt for the low battery it is a problem (though usually only one week a year if you install the same smoke detector in all rooms at the same time. And it is hard to find because it emits a high chirp every 30-60 seconds but that chirp echoes throughout the house and is hard to pinpoint (especially if you do have 1 in each room).

But I agree loud and sensitive better than the alternative and you can avoid accidental set offs by not having one located near the kitchen stove, though most of the time bad smoke detector locations are in apartments where you wouldn't have a choice to move them anyway.

> But I agree loud and sensitive better than the alternative

You don't have to choose! If you want the loud alarm to go off when it detects X PPM, have a gentle alert go off when it detects (0.9 * X) PPM.

The Nest is a photoelectric smoke sensor. The Kidde is an ionization sensor.

"Kidde strongly recommends that both ionization and photoelectric smoke alarms be installed to help insure maximum detection of the various types of fires that can occur within the home."

More info: http://consumerist.com/2010/08/25/fire-chief-most-smoke-alar...

Interesting. It's sad, then, that Nest does not emphasise that fact.

From a safety only perspective:

1) This doesn't detect carbon monoxide 2) One of the 1-star reviews states that Ionization alarms are old technology and unsafe compared to newer piezoelectric alarms.

Photoelectric.

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