They have about a ten year lifespan so id imagine that one doesnt work.

Is it hard wired? just rip it off.

Does the house have new / working smokes?

They need to be replaced every 10 years in any event. Use a bigger hammer. (Chances are good it will come off if you twist hard enough.-- put a strap wrench on if if you're not strong enough)

• What it is
• How to open it (it's likely attached to an electrical box in the wall)

@Dave: Thanks. Yes the house do have new / working smoke detectors in the hall ways and in the bedrooms, etc. But not in the main living room. I think it is hard-wired but I'm not 100% sure... Thanks!

Why did you say that a smoke detector has 10 years of lifespan? Is it planned obsolescence (that they will just go bad after 10 years, even with good maintenance and regular changing 9v batteries)? For the new lithium battery type of smoke detectors, I can understand why they have 10-years of lifespan, but for 9v battery operated smoke detectors and hard-wired type of smoke detectors, shouldn't they last for much longer? Thanks!

@wdccruise: WOW! You are amazing! How did you find out the model# of my smoke detector? I tried to use the Google photo "Lens" feature and was only able to find some closely matched smoke detector, but you actually was able to find the identical one with the correct model# (ESL model 445CT)!! Amazing!!!

Do you know when (roughly) it was made (just curious about its age)? Also between ESL 445C, 445CT, 445CR and 445CRT, do they all look the same? It looks like it's a four-wire system. Can it be easily replaced by a modern Smoke Detector like the Amazon best seller First Alert 9120B Smoke Detector (hardwired)?

@Stax: Just a quick FYI - eBay is selling these vintage smoke detectors for $80 a piece! :)

Thanks!

Smoke detectors all just have a 10 year lifespan. There are more wear parts in them that just a battery. The sensors may not perform as well after a certain amount of time.

" Is it planned obsolescence (that they will just go bad after 10 years, even with good maintenance and regular changing 9v batteries) "

Life safety is a bit more important that why they have a lifespan limit.................

The sensors lose sensitivity with time, apparently the failure rate of the electronics is about 3% per year. Since pretty much no one tests their home fire alarms, the folks who worry about such stuff (like NFPA) decided that replacement every 10 years (~25% of detectors no longer working properly) was a reasonable compromise, especially given current code requirements for redundant coverage with multiple detectors.

By the way, Is it better to replace a hardwired smoke detector/alarm with a non-wired lithium-ion battery smoke detector/alarm? Why and why not? And yes I have existing wiring. Thanks!

Generally the hardwired detectors connect to each other so that when one triggers they all sound. This ensures that you hear it when one at the far end of the house goes off and you're at the other end sleeping behind a couple of closed door. So yes, I'd definitely go with interconnected alarms, certainly if the wiring is already in place.

If theyre already hardwired, theres no reason to switch to battery only. Hard wired all talk to each other and thats the benefit.

@rwiegand @Dave: For older houses (built in 1937), can the existing wire go bad for these hardwired smoke alarms? How do i test the wires? Also, if the house already have some wireless lithium battery operated smoke detectors installed (Kidde brand), is it better to stay with Kidde (home depot) branded hardwired smoke alarms, or it doesn't matter? I guess there is no way (and probably not a good idea) for all the wireless (lithium battery or 9v battery operated) and hardwired smoke alarms to "connect" to each other and have ALL of them sound the alarm at the same time, right? That would probably be super loud, and it can be difficult to identify which room actually has the smoke? Thoughts? Thanks!

Also, the original owner installed an old "hardwired" small smoke detector (alarm?) right above the range hood. I think the location is kind of weird. Given the modern/new smoke detectors might be more sensitive (using latest technology), I don't know if we replace a new/modern one, it would be triggered all the time. Thoughts? I'm also curious about what's the model# and manufacturer (as well as the possible year of manufacturing) of this smoke alarm? Is this a standalone smoke detector, or is this something that would connect to a central security/alarm system that was used in older houses? Thanks!

That's a heat detector. Smoke from burned toast or broiling won't activate it but when heated air reaches a certain point (maybe 135F) it will go into alarm, the rating is probably marked on the outside on the thing that looks like a label on the right edge. They usually can't be reset, they are single-use only.

W Chuang, I have the same smoke detector and I'm trying to replace it as well but cannot get it open or twisted to remove. Did you have any luck in getting your detector off the wall? If so, what did you do?

"Try opening the cover on the detector. It should snap open and swing out like a door.

"Don’t forget to put a paper clip or tiny flathead screwdriver in the slot on the side of the black base opposite that silver dish...to release the cover." -- Reddit

" Ten-year sealed battery smoke alarms are powered by sealed lithium batteries that have a life span of ten years. These alarms provide 10 years of continuous protection with no need to replace the battery for the life of the device."

Some locales prohibit the installation of detectors with 9V batterys and mandate replacement with 10 year batteries!

There is a little slot on the side on the black part. A small punch iror awl pressed in and it will swing down. If you can tell which side the hinge is on then the slot will be on the opposite side.