Do I need to replace them all?

[MTNesters]

Our home has six somewhat old smoke detectors. Three of them are not functioning properly. Can I simply replace the three troublemakers with Nest Protect, or would I have to replace all six? What concerns if any would I have if I only replaced three of them? TIA

[DanCoco · Accepted solution]

I was a firefighter for several years.

From a fire safety position, Smoke detectors should get replaced every 10 years, 7 years for CO. Deciding to keep the remaining 3, or replacing all would depend on your specific situation. Can you replace 3 detectors with linked alarms that can be heard from anywhere in the house? 

Often times problems with electronics can happen in manufacturing batches. Staggering your replacements to half now, half in 2 to 4 years, could be better (if they are in decent shape.)

I would recommend against Nest Protect if you would like to use the app in any fashion, as it will not appear in Google Home for the forseeable future if at all. ("Soon, maybe" is the official answer.) I do not get accurate alarm notifications, they are very delayed if they come at all. No feature exists to allow detectors to control home functions like turn on all lights and unlock all doors. 

One advantage to Nest Protect is it is a linked alarm, meaning it will alert the other protects in the home, so they all go off, telling you where the smoke is. They also self test, so you wont cringe when someone asks you "when did you last push the monthly test buttons?"

In my house, i have 3 bedrooms on a second floor. Each bedroom has a basic non linked smoke detector, with a wired Nest Protect in the hallway, center of all 3 doorways. I have a second Protect at the bottom of the basement stairs. I was going to add another protect on the first floor, but refused to buy after Google Support broke my Nest account, crippling phone alerts to alarms, among other things. The alarms do still set each other off.

My reasoning for the mix of linked and "single station" alarms is that any floor could have a fire and the connected detectors would go off close enough to be heard. The 2nd floor hall detector is loud enough to be heard in any bedroom, with the in room detector as backup. And over 600 dollars in smoke detectors was outside my new homeowner budget at the time, hence the mix.

Unlinked alarm scenario:

If my basement door is closed, and a basement fire starts, i would not hear the basement alarm from the second floor bedroom in bed. The fire would need to grow to generate enough smoke to get thru the furnace ducts (if its running) or burn through the door or floor to allow enough smoke to get to the 2nd floor detector. My 2nd floor stairs are over the basement stairs, eliminating that exit. the escape time lost may be too great, possibly cutting off hallway access, plus needing to window evacuate.

Linked alarms:

That same basement fire generates smoke and rises, filling the basement stairway, setting off the basement detector. The 2nd floor detector goes off "Heads Up! There's SMOKE... In the BASEMENT."  Now not only do i have a few extra minutes to get out, i know what area the fire is in vs just hearing beeping. This might make the difference in being able to get into the hallway at all to access the other bedrooms and see if the stairs are still a safe exit, vs having to go for the backup exit, not being able to wake anyone else up.

This would work with any brand of connected alarms. Sit down and think of your layout. You want a detector per bedroom, one in each bedroom hallway, and one minimum on each floor. Keep into account doors that are typically closed, cathedral ceilings, creating different "air pockets" Then determine if you want/can afford to have a fully connected system or a mix like me. 

(And close your bedroom door at night unless pets need in or out.)

[MTNesters]

@DanCoco:  Thank you very much for your prompt, thoughtful, and thorough reply.

[Natewagner]

It is recommended that you have the same type of smoke detector in every room, that way in an emergency they communicate to each other and they all go off in every room instead of just 3 rooms. Nest protects can be expensive so I’d either get 6 nest protects or 6 standard smoke alarms

[DanCoco]

This would be fine as long as they are linked alarms. Otherwise, it is safer to have 3 linked alarms, and 3 single station  (unlinked) alarms for the reasons listed above, rather than 6 single station alarms.

[aatienza]

Hey folks,

Checking in — we hope you've got the answer you're looking for. Let us know if you have more questions in mind.
 

I appreciate the help, DanCoco.

Thanks,

Archie

[MTNesters]

As the OP, I'd say I got all the information I was looking for and more. If you're looking to close this thread, I wouldn't object. 

[aatienza]

Hey there,

Got it — let us know if you have other questions as I'll be locking the thread after 24 hours.

Thanks,

Archie

[MTNesters]

Lock away, sir. 

[janthadeus]

Hi MTNesters,
 

As you’ve requested, I'm going to close this thread and mark it as complete. Feel free to create a new one if you have more questions or have other concerns in the future. 

Thanks for the help here, everyone!

Best,

JT

[MTNesters]

@Natewagner: Makes sense. Thanks to you as well.