Why do they always chirp at 2am?

A non functioning fire alarm. Ready to be retired.

A newer alarm in the same home. Tested and in good shape.

What is that noise?
Picture this, you are sound asleep and you hear a small chirp. In your sleepiness you decide to ignore it and it happens again. You think to your self, "I don't know what that is but it better stop." Then it happens again and now you are awake enough to recognize it as the dreaded sleep deprivation device......the smoke alarm. If you are married you might think to yourself "maybe they will get it." They are likely thinking the same thing. Finally you have had enough and decide the best course of action is to remove the offending life saving device by methodically hitting it with  broom until it is laying on the floor, silent. Mission accomplished and back to bed you go. 

This can be a common scenario for many households but it does not have to be. Smoke alarms are when properly maintained and tested have the capacity to help save our lives and the lives of our loved ones. Think of them as having a full time fireman that works 24/7 365 and all they ask in return are fresh batteries, be tested once a month, and to reach retirement in 10 years. They are not asking a lot in return for performing a very important task. 

Things to keep in mind:
Test each smoke detector at least once a month. If you haven't tested them recently, do it now!  
Have the batteries been changed in the past year? If not change them now. (Some alarms do not have replaceable batteries.)
Check the expiration date. Are they ready for retirement? If you can't tell, replace them. 
Note where they are in the home. Are they in every bedroom, outside of each sleeping area, on every level and the basement?
Are they wired together and all sound at once or do they operate individually? 

ProTip - A few minutes a month of preventive maintenance and testing can and has saved lives. You and your family are important to all of us. Please check your smoke alarms. 

More info can be found at:
https://www.usfa.fema.gov/prevention/outreach/smoke_alarms.html
https://www.usfa.fema.gov/downloads/pdf/publications/infographic_2016_fpw_custom.pdf