Smoke detectors, Ionization vs Photoelectric

[Sid 03]

Looking to install some new smoke detectors. I was going to install Ionization type smoke detectors in the lower floors and then a combination smoke and CO detector on the 3rd floor where the bedrooms are located.

I noticed that most of the combo detectors do not use ionization to detect smoke, but use photoelectric type sensors. Is this a a big deal or should I stick with the most popular ionization type ? Years ago I was told by a contractor to not install combo detectors, but to keep the CO and Smoke detectors separate ? Does anyone have an opinion on that ?

If the CO detector has an interconnection wire for other alarms, should you connect it to the interconnection wire for the fire-Alarms ? All this stuff is manufactured by Kidde, so I am assuming that is all compatible ?

Thanks Sid.

[Ed Pawlowski]

My house has combo units installed by the builder. No particular opinion on them., they seem to work. In my last house they were separate.

One question though, give where you plan to locate the CO detectors you are taking precaution not to die in your sleep at night. Do you thi k it is better to fall asleep on the sofa and die fro CO there?

There should be one on each floor including the basement. Not right next to the heater though. If you have a garage in the house put one near the door to the garage. People have left cars running and died.

[Dean Hoffman]

This is what Consumer Reports has to say. They haven't tested them for a couple years.

This is as of June 2018.

Consumer Reports wasn't satisfied with any combination smoke and carbon monoxide detectors they tested then.

These are the dual sensor smoke alarms. First Alert 3120B $30 Score 91 Kidde P12010 $30 Score 91 First Alert SA320CN $23 Score 87 Kidde P19010 $25 Score 87

Ionization smoke alarms. First Alert SA9120BCN $25 Score 55 Kidde KN-COSM-1B $35 Score 55 Note 1 Kidde RF-SM-DC $40 Score 53 First Alert SA303 $12 Score 51 First Alert SA304LCN $24 Score 51

Photoelectric smoke alarms First Alert 7010B $25 Score 55 Nest Protect $129 Score

55 Note 1,2 Nest Protect $129 Score 55 Note 1,2 First Alert SA501CN $60 Score 53 Note 2 First Alert SC051CN $70 Score 53 Note 1,2

1 Combination smoke/carbon-monoxide alarm, also rated as CO alarm.

2 Interconnects wirelessly.

[invalid unparseable]

I knew that CO detectors had a finite lifetime, 7-10 years, and now note that smoke detectors are recommended to be replaced by 10 years. Still not sure a combo appeals to me since I got over 20 years out of two smoke detectors before I replaced them.

[hubops]

I think the 10 year "lifetime" is a recommendation that will provide acceptable reliability - beyond that, the device may still be OK but the crucial reliability begins to decrease. I'd be OK stretching it to 12 years, not 20. John T.

[trader_4]

I don't understand the scoring. The combo ones are all way higher than the smoke only. Does that mean that the scores for the dual units were a number for smoke plus a number for CO so those numbers don't directly compare? Did they have some explanation or reasoning as to why the dual units were not as good?

[FromTheRafters]

Sid 03 expressed precisely :

CO is heavier than 'air'. Smoke is generally in hot air and rises.-- follow their instructions for placement.

[invalid unparseable]

Yes, from what I read now, that was a stretch. I recall my wife accidentally testing the first floor unit on occasion with inadequate stove ventilation. Also the finite battery lifetime gave a test that they still worked by alerting us with beeps of impending battery failure.

[invalid unparseable]

Heavier?

CO 28.01 g/mol N2 28.0134 g/mol O2 32.00 g/mol

[FromTheRafters]

I stand corrected. Smoke rises, and CO, generally, does not.

[danny burstein]

[snip]

Carbon Monoxide has an atomic, well molecular, weight of Carbon [12] + Oxygeb [16] ==> 28

Air is a mix of lots of stuff, but if we just look at nitrogen, which is 78 or so percent of it, N2 => [14 times 2] => 28

plus, of course, these gases don't remain as discrete entities but mix in with each other.

So CO is going to be pretty much diffused throught the air.

[FromTheRafters]

danny burstein submitted this idea :

Yes, thanks to you and Frank for making this clear.

[Sid 03]

Thanks for all that info. What about the interconnection wire ? Does that have to be the same gauge as the other wires in the box ? I believe the harness is 18 gauge. Why can't I just run a piece of bell wire between the detectors ?

[FromTheRafters]

Maybe their online manual will help?

[AJL]

I bought detectors with 10 year permanent batteries installed. When the batteries finally complain or the 10 years is up I'll replace them with another ten year bunch. Unless of course they outlive me.

[Sid 03]

I went out and read the entire user manual from Kidde and it does state that the max distance between interconnected-wired units is 1000 feet, but nothing about the type of wire or wire-gauge that can be used.

[Wade Garrett]

One other thing to make clear. Avoid the Kidde 10 year battery models. I've had several and most only last a few years.

The good news is they (used to) replace them via warranty. The bad news is they are on back-order now. Mine died two months ago and I called them but they told me it will be several months to be able to send me a new one.

Screw Kidde. I went to the store and bought a competitor's product. It's working fine!

[AJL]

My 10yr battery models are First Alert. After 3+ years so far so good. Dunno what the warranty was but I'm probably SOL if they quit now.

[micky]

You should use at least one of each. They are different and they detect fire differently. If you want to detect all your fires as soon as possible, and not just some of them, you want both kinds.

I had a problem for a while when I started cooking meat in frypan. It would set off the smoke detector which would set off the siren and call the alarm monitoring company, which woudl have called the fire department if I were not home, but of course I was home or I wouldn't have been frying at home.

But by not making the pan quite as hot, I still cooked the meat, it came out the same and no more men in big brim hats visited me.

Well if half breaks, you're torn between keeping both halves or throwing away both halves, but I don't know how often half breaks that the other doesn't

[micky]

I think they sell ones with 6-year batteries for 104-year olds.