Our smoke detector started randomly beeping last night about midnight so I immediately changed the battery, but it's still beeping! I'm pretty certain it's not hooked up to mains power or the security system.

I took out the battery to clean it and it beeped even without the bloody battery! I gave it a dust but couldn't get all the dust off.

Is it just old? I tried taking the battery out and pressing the test button to reset it (as per googles instructions) but nothing happened.

It's driving me insane and I worry about it not working.