why do smokes randomly go off??

[RexT]

Hi guys,
I agree with the above comments and there are a number of reasons why a smoke alarm / detector may be triggered into alarm state.
One way to think of them is that they are designed to detect particles and as said above dust or any particles can cause this. The key is to use the correct type of detection in the correct location. Maintenance is an important issue and in domestic smoke alarms this is rarely done correctly.
Using a vaccuum to remove dust on a regular basis from around the entry ports of a detector normally is beneficial and gives the unit the most life. However once the unit is contaminated they are not designed to be easily opened and as such the damage will have been done. Most contaminated units react by being more sensitive than normal depending on the level of contamination.
I think Bill is right and replacing the batteries with good quality ones is a good thing on a regular basis. Most are designed to provide a warning when the battery becomes low or out of specification. Some units monitor the sensor and this also can give a single chirp alarm.
Hope this helps,
Best wishes
Rex

 

[Tillywolves]

I remember being called out to an old peoples complex. Fault was reported by occupier of room that the smoke alarm keeps going off...

Got there, and it was a conventional fire alarm system, not domestic smokes. The detectors didnt have an internal battery or sounder. Told tenant that it wasnt the fire alarm that was going off..

As I was leaving the home, the warden called me back, as the tenant, an old lady, had just called her on the intercom, and said the smoke detector is sounding again...

Bemused, I went back to the room, and the lady was adamant that the siren was going off.... I sat in her room to see what was causing the noise. Minutes later the woman said, "its there again, I can hear it." It turned out that the noise was her hearing aid feeding back...

Sometimes you just cant trust what someone is saying to you....

The smokes could be faulty. Are both going off, or just one. You could temporarily remove the link between the two units, to see if it still happens. Then replace the faulty one.

The majority of false alarms I get with opticals, are ingress of dust or insects.

 

[IQ Electrical]

Had a callout just before Christmas to a workshop using extra gas powered heaters to combat the low temperatures, the condensation at roof level was dripping from the steels and triggering the smoke detectors.

 

[manda]

I stripped and decorated a friends hallway last year, the dust totally wiped out the wired in smoke alarm, even though I'd disconnected it and put in another room. It still managed to get in the sensor! Luckily it was a council house so the council kindly fitted a new one. Next time I'll save myself the hassle and put them in a ziploc bag too!

 

[IQ Electrical]

Were you shot-blasting it?

 

[manda]

Lol. The walls were atrocious so there was plenty of filling, sanding and patch plastering going on. By the time it was done I was wishing I had never offered!

 

[Des 56]

Builder phoned me the alarms were going off at an house belonging to a gay couple
Told him to disconnect until I could get there

The builder being in his own home explained the procedure to the couple

He phoned me back a little later "They say the alarm is still going off "
I say "Did they disconnect them from the base"
"Yes said the builder but they are still sounding"
Then tell them to throw them out on the garden says I

Builder phones again "They have thrown them in the garden,but they are still going off"
Remember only the bases are left

Long story cut short,builder travels over and alarm is sounding
Its the old story of an unused battery alarm stuck in the bottom drawer and forgotten about

Its amazing that people can honestly believe that a base of a smoke detector can emit noise,but these 2 would not be convinced till the "fault" was sorted

 

[jaresquire]

On one of my commissioning jobs for a fire alarm in a multi million property refurb, the client decided to repaint (for about the third time) after the fire system was up and running and monitored. He found a box of latex gloves to act as dust covers for the optical smokes. Unfortunately there is something in the latex that triggers smokes, which cost two visits by the brigade. Still not sure what the chemical is but I could do with it in a test spray.

 

[millwall ken]

Builder phoned me the alarms were going off at an house belonging to a gay couple
Told him to disconnect until I could get there

The builder being in his own home explained the procedure to the couple

He phoned me back a little later "They say the alarm is still going off "
I say "Did they disconnect them from the base"
"Yes said the builder but they are still sounding"
Then tell them to throw them out on the garden says I

Builder phones again "They have thrown them in the garden,but they are still going off"
Remember only the bases are left

Long story cut short,builder travels over and alarm is sounding
Its the old story of an unused battery alarm stuck in the bottom drawer and forgotten about

Its amazing that people can honestly believe that a base of a smoke detector can emit noise,but these 2 would not be convinced till the "fault" was sorted

Are you really surprised Des that some people REALLY can be that thick?

 

[leeweimaraner]

thanks for pointing out the colours used today??????<<<<>>>>....the yellow that i am talking about comes on the smoke alarm it has a brown (phase) blue (neutral) yellow (monitoring cable) what i was trying to say he may have connected the yellow as an earth so when you plug this into the smoke alarm it creates an inbalance tripping your rcd.

 

[accordfire]

thanks for pointing out the colours used today??????<<<<>>>>....the yellow that i am talking about comes on the smoke alarm it has a brown (phase) blue (neutral) yellow (monitoring cable) what i was trying to say he may have connected the yellow as an earth so when you plug this into the smoke alarm it creates an inbalance tripping your rcd.

I see. That wasn't clear in your first post.

That said, I'm not aware of many smoke detector which have flying tails in them any longer. What brand of detector are you using?

And in principle, you're totally right - connecting an interconnect signal to earth will trip an RCD.