It's time to change the batteries in all of your CO2 and Smoke Alarms.
Why
Do we really need to tell you why?
How
It's a good idea to synchronize changing your smoke and CO detector batteries with the changing of the clocks. Once the new batteries are in, hit the "test button" to make sure the alarm is functioning properly. If it isn't working properly, run (don't walk) to your nearest hardware store and replace it. Vacuum dust off of the units and wipe clean if necessary.