So at 3.30am this morning my wife wakes me up, stating that the smoke alarm in the upstairs hallway is making a noise about every 30 seconds, and that she wont be able to sleep until it stops. Despite looking, she cannot find any way to make it do so.

Sure enough - "CHIRP!". Not the, 'Get out of your house now', adrenalin-pumping alarm but the, 'This is going to annoy the hell out of you', intermittent chirp. After bemoaning the fact that it was interrupting a bizarrely interesting dream(*), I dragged my butt out of bed and went to look at it.

"CHIRP!". The sound reverberates around the small upstairs hallway, and rattles through my semi-conscious brain. There's definitely no smoke here, and it must be a fault code. Probably a dying battery. I examine and pry at the device but it doesn't easily open. Maybe it'd be easier if I could see what I was doing. I retreat to the bedroom to get my glasses.

Ah. Twist anticlockwise. With a simple pronation of my wrist, the body of the device separates from it's backing plate. Then I notice the wires extending into the wirebox behind and foggily remember that this is an AC smoke alarm, and connected to its brother in the basement. Still can't see the back up battery, or any hatch that might lead me to one. Puzzled, I wonder if maybe only one unit has a battery backup in it, and decide to check out the basement detector.

So I get dressed and visit the unfinished basement. Find the smoke alarm. Sure enough - there's a battery. I remove it and do the tongue test. Seems fine. Put it back in and hit the test button. I quickly release it due to the painful screaming in my ears. Oddly, this one appears to work fine.

Hang on...now I am awake, I notice that something is wrong. This smoke detector is attached directly to the underside of a 150 year old wooden beam and I can't see any wires protruding from it. Not only that. but it is quite obviously made by a different manufacturer.

Ok. So apparently we have two smoke detectors in the basement. I hunt around and locate another. I sanity check that it is mounted on a wirebox. Yep...and it's identical to the one upstairs. No obviously accessible battery either. No chirping, and the test button deafens me.

At this point, I decide that discretion is the better point of valor, and that the desire for sleep is beating back every geek tendancy in my body. I admit defeat and surrender to the RTFM urge. The only problem is that I don't know if we have it - the smoke detectors have lived here longer than me.

I memorise the model number and retreat to the office. Praying to Google, I soon locate the manufacturers web site and click on their tech support link. Then I find out that they only keep manuals online for their latest models, and the only information relevant to these ~8 year old detectors is their generic FAQ. This is about as useful to me as a chocolate teapot(**). It's trying to tell me why I should install a smoke detector and how the radiation source contained within is 1000 times less dangerous than background cosmic radiation from the sun. Hello! Earth to Major Tom. It's 4am in the morning and I'm not getting any sleep. Someone tell me how to shut this tucking fhing up.

I go back upstairs to take another look at the offending device. "CHIRP!". I wonder if maybe a bugs got into it and whether a blast of compressed air would help. As I study it closely, I notice that the body will separate further - there are some tabs hidden under the manufacturer labels. Hmm...Screwdriver job. Maybe it does have a battery after all. I unplug the damn thing from it's wires so that I can work on it in comfort downstairs. "CHIRP!". Aha! Battery!

I rush downstairs to my desk. I pull a small screwdriver out of a drawer, poised to attack, victory will soon be mine.

"chirp!". Whoa. Where did that come from? The basement?

My head spins. Has the basement detector decided to complain about my unplugging to the upstairs unit? Why? WTF could that mean? I want to find the engineers responsible for designing this thing and subject them to my pain. A month of 24x7 "Enter Sandman" at 90dB ought to do it. "chirp!". Again, the unit in my hand remains quiet.

I put down my screwdriver and wander towards the basement door, deciding upon the way that I'm just going to leave both detectors unplugged until the morning.

As I get close, "Chirp!", I realise that the sound is still coming from upstairs. WTF!?

At that moment I have an epiphany.

I walk upstairs and reconnect the smoke alarm. Then I turn around and pick up the carbon monoxide detector that hangs barely 4 feet away on the opposite wall. Low battery.



(*) It was strange. It was like at the end of a paintball match where everyone excitedly discusses their fortunes duing the match, who they shot, how they died etc. Only we were all in some kind of afterlife and the bullets had been real. The discussion was totally matter-of-fact, no negative emotions. It was simply ok - everyone there was friendly. Weird.

(**) Actually, less useful. I could eat a chocolate teapot.