HELP - smoke alarm going off but we can't find any smoke

[nearlythree]

Please help if you can. Our smoke alarm went off in th eearly hours but we can't find any smoke. We live in a chalet bungalow and have three kids under five and I am sick with worry. I've tried ringing th elocal fire service but keep getting answerphones. Can anyone give any advice on who to call or whether this is anything to worry about in the first place?

It might need a battery change or some unusual heat source might have set it off.

Was it light when it went off? The sun might have shone off a mirror onto it or something?

get a new battery as that does happen...

Thank you for all your replies. It doesn't have a battery as it's wired into the mains. There isn't a mirror nearby but the sun was coming up, maybe that could have done something?

the wiring might have moved - can you have a look to make sure a wire hadnt fallen out

It could be steam from the shower or it could be a tiny spider . I am not joking