This morning at 5:10 all our smoke detectors went off. We all bolted out of bed and tried to figure out what was going on. No smoke, no fire. Our CO2 detector didn't detect anything. Regardless, we rounded up the kids and cats, jumped in the van and parked at the end of our driveway. DH called the fire department (non emergency #). They showed up with 3 trucks and about 10 fire fighters. No sirens, thank God, or our neighbors wouldn't have been pleased. They went through the house with their smoke/CO2 meters and found nothing, but did find a defective smoke detector. Our house is set up so that if one detector goes off they ALL go off. Very loud and annoying, but good in the event of a true emergency. I'm glad it was a false alarm, but my goodness, what a rude awakening!