Alarming Smoke Alarms

[xl5]

A few weeks ago my Daughter's smoke alarm decided to go off at 3am (no obvious cause) wakening all including neighbours now this is a mains driven device with back up batteries ( button type) situated at the top stair landing the 2nd one is located in the downstairs Hallway.

My Daughter lives almost next door from us and we were rudely awakened by her saying the alarm could not be silenced, being still in a haze and with many decibels right next to my ear i snipped the output source wire until the 24 hour service arrived to rectify the problem and when they eventually came they replaced the whole unit.

Very recently the same scenario happened about the same time in the early morning except both smoke alarms sounded

Even sleepier than the previous encounter snip snip phone 24 hour service arrived hours later and replaced both units.

Summing up;. The mains supply was not interrupted on both alarm occasions.
If the batteries had failed would the mains continue to supply the detectors without sounding the alarm ? and surely if the mains supply failed the backup batteries will take over with no alarm sounding this is intriguing to me, can someone explain! Bearing in mind that both alarms went off at the same time few week's later with new batteries fitted.

NB: Both smoke alarms are now replaced and i am sleeping better.

 

[Sceadwian]

I don't like the idea of mains powered smoke alarms, it's adding a failure point to something that is already as simple as it can get. If it has backup batteries they'll have to be replaced every 5 years minimum, it's a better habit to get into changing the primary cell out of a battery powered unit once a year every year forever.

Obviously the smoke detector units in your house are faulty, again this is why battery units are superior in every way.
You replace the battery once a year, you replace the unit once every 5, outside of freak failure you're as covered as you can get.

Considering the cost of the units and batteries even over an entire lifetime, no insurance policy can cover those extra few seconds warning a basic reliable unit can give if your more complex system fails (as it did) in gloriously false alarm fashion.

 

[Gary B]

Is there any chance that the alarm also monitors CO? If two go off, it is time to investigate the possibility that they are working and there is something dangerous in the environment.

 

[Reloadron]

I could understand a failure of a single unit but two at the same time leaves me wondering. I would take to heed what Gary B mentions and look for any other hazards that could be triggering the alarm(s). This is especially true if the new units begin to fales trigger as the false may be a true for a hazard.

There is no mention if the dwelling is an apartment, condo, or private residence which brings us to Sceadwian's comments regarding power. I agree and have seen countless smoke detectors installed in apartments powered by mains power. Actually there is a reason for it.

The 2007 Residential Code of New York State reads in part:

[F] R313.1.2 Power source. In new construction, the required smoke alarms shall receive their primary power from the building wiring when such wiring is served from a commercial source, or an on-site electrical power system and when primary power is interrupted, shall receive power from a battery. Wiring shall be permanent and without a disconnecting switch other than those required for overcurrent protection. Smoke alarms shall be permitted to be battery operated when installed in buildings without commercial power or an on-site electrical power system or in buildings that undergo repair, alteration, change of occupancy, addition or relocation in
accordance with Appendix J .

The above quote taken from here.

Most states have similar codes for apartments and condos. Given a choice I want a battery in the thing!

Again, if the newly replaced units make so much as a peep I would be looking for the reason why.

Ron

 

[Sceadwian]

The bulk majority of smoke detectors use a radiation source to irradiate a gap, any particulates (dust/smoke) entering the gap ionize and provide a conduction path for the alarm circuit. If something is really setting off the alarms, that's what it requires, particulate matter of a certain overall density in the gap.

Could it be wall plug type scent dispersers used nearby? There could be a lot of other things that could in theory set off a smoke detector. The question is will the replaced units go off.

 

[ben7]

I don't like the idea of mains powered smoke alarms, it's adding a failure point to something that is already as simple as it can get. If it has backup batteries they'll have to be replaced every 5 years minimum, it's a better habit to get into changing the primary cell out of a battery powered unit once a year every year forever.

Obviously the smoke detector units in your house are faulty, again this is why battery units are superior in every way.
You replace the battery once a year, you replace the unit once every 5, outside of freak failure you're as covered as you can get.

Considering the cost of the units and batteries even over an entire lifetime, no insurance policy can cover those extra few seconds warning a basic reliable unit can give if your more complex system fails (as it did) in gloriously false alarm fashion.

The alarms in my house are mains powered, and they have had no problems.
they have backup 9volt batteries.

Also, my dad is a firefighter, and he says a false alarm is better than an actual fire!

 

[xl5]

Hi, there isn't a gas installation in this semi detached property (all electric) at 3am no cooking frying taking place also no scent spray dispensers or steam near the area's smoke detectors. still bamboozled but so far since both detector's have been replaced there has been no problems.

Thankyou to those who contributed to my post.

 

[ben7]

This is such a weird problem, besides the alarms being defective!