green-foam

I agree with Tom, Carbon monoxide is generally considered to be the same density as air, but since it is often hot, it rises. I would guess (and it is only a guess) that your electrician is either confused or misunderstanding about carbon monoxide, allow me. Carbon monoxide is the same density as air and so it generally sits there. Its chemical formula in words is CO Carbon dioxide is heaver than air and will always fall to the lowest point that it can. Its chemical formula in words is CO2 I often find that people do not realise this fact and will often call a carbon monoxide detector a carbon dioxide detector or label its supply as "CO2 detector" when it should be "CO detector" I am guessing your electrician thinks that any carbon monoxide produced will "fall through the gap in the loft hatch" and activate the alarm. As I said carbon monoxide will not do that but carbon dioxide would fall through the gap. (But not set off a carbon monoxide alarm) Carbon dioxide is what makes fizzy drinks fizzy. And is only lethal in large volumes Carbon monoxide is the product of improper combustion and is lethal in minute volumes.

I would take that further and say anyone who is NOT a fire alarm engineer gets a "Frosty reply"

If you could add non addressable call point to the system (I don't think you can) would that not defeat the whole idea of it being addressable? (You would not know which call point had been operated)

I have to ask, what is this refillable air cylinder for, and what regulator and hoses have you got (what are they for)

I would suggest this is more of a legal matter than anything else. My thought would be to ask them to look at your device and take it from there / seek legal advice.

Poking wires back into the ceiling? what would happen if there was a fire? Nothing because you had poked the wires back in the ceiling, Do as Harry suggests change just the detectors and have peace of mind

I for one do not believe it is your alarm making a noise. I am suggesting it is something entirely different which may or may not be supplied by the mains (I would say its not) The other suggestion would be to ask is there a loft space? and if so have you looked / listened in there.

I would be inclined to agree with Harry, but for similar reasons. The base has no sounder, but even a smoke detector does not have a "timer" as such, and as you say it happens at the same time once a day, that implies a timer of some description and what better timer / sounder than an alarm clock or maybe an old mobile phone, in a drawer maybe?

Without further information I can not see how any one can be of help to you. Information such as make / brand of light Is this light in a fitting or is a it "Just a huge single LED?" Has anyone been working on the lights Anything else you may think relevant

Stand alone battery smoke alarms will continue to sound until the air is clear from smoke or the battery runs flat. If you can not reach one that has activated for a known reason I can only suggest you "waft" something slightly solid (Folded newspaper at worst) under it to dissipate the smoke.

I would have to ask, are they "fire alarms" or are they "smoke alarms" I will guess you mean smoke alarms, the interesting thing is, you say they only went off at night, and several nights in a row. From that I have to ask would any one have been down stairs, may be making toast and forgot it and it got burnt? The other question is since you first asked your question, has it happened again? If the answer is no, I would say that what ever was causing the smoke alarm to activate is no longer there. If the answer is yes, next time it happens go straight to the detector and look at it , see if you can see / smell anything "odd"

Thing is..............the job has probably been done by now as it was asked back in 2016

To me your question seems some what vague, could you explain more? Audibility test of what? How would you know if this audible "thing" is audible enough? What is this audible thing your customer needs a certificate for?

If it helps a 6kg lasts around 16 seconds.

Wait for it to stop (It probably has by now)

The problem with carbon monoxide is it colourless and odour less (So you can not see it) As there are renovations going on below you and the CO alarm has been ok previously its safe to assume its something the people doing the renovations that produced carbon monoxide. But as I said, they would not know they are producing carbon monoxide because you can not see it.

Have you taken the battery out of each smoke detector? (You only mention removing the mains)

Doubtful it is the tube (I assume it has hardly ever been lit) So that means the batteries have probably failed, they only have a working life of 3 - 5 years at most. Safelincs can supply you with batteries from just under £12 Click here Or you can as you suggest change the whole fitting. Safelincs can supply EM lights starting from just over £15 Click here

Since one will work with out the other it would suggest an incompatibility problem. You say you changed two smoke alarms, are there any more interconnected? if so remove them and put the other new one back to see what happens. Also make sure the connections are the same at any detector and that there is no junction where the colours could have been swapped.

Chirping every 90 seconds indicates a low battery. You need to change the batteries, I would change the batteries in all of the detectors. Most folk do not realise that although a smoke alarm is often supplied by the mains most also have a back up battery.

Not wishing to as pedantic as it may sound, but I will say you found a CO alarm, not a CO2 alarm. CO is carbon Monoxide and is the same density as air, its a by product of incorrect combustion. CO2 is carbon Dioxide and is denser than air, it is also what makes fizzy drinks fizzy and is also used in fire extinguishers,

If any soft toys are affected you can clean them but it will take a lot of time and effort, that said some may be washable (read the wash care label, if it hasn't got one don't wash it) but if you dispose of the affected toys, there will never be any doubt.

If it helps, I have some CO2 extinguishers here at home that are old, they never get serviced, and they are still full of CO2. (I know they are full because as Tom points out, its easy to weigh them) As an aside, if the contents were to cease to be CO2 what would it be? I have also had one that leaked (after being used in a video) it was so bad you could actually hear it hissing / crackling.

People often say "oh it's faulty" (About most things) when in fact it isn't. Carbon monoxide itself is odourless and colourless I would suggest that your CO detector did indeed detect carbon monoxide and that is why it activated (It was doing its job) As for where the CO came from, no one can say, but I would check that your CO alarm is working by pressing its test button and making sure it is within its age limit. (They have a life expectancy of between 5 - 10 years, depending on make / model)

{thinking out loud} polyvinyl chloride is more commonly known as PVC or plastic, so although it may self extinguish, it would melt / disfigure so letting in smoke, also in the text it says would make them Fireproof, it does not say "does" make them fire proof. {Thinking out loud}