There are 4 things you could do to fix the annoying every 30 seconds beeping coming from your hard wired smoke detector. Before you actually do any fixes, make sure you have turned off electric power to that hard wired smoke detector by switching off the power supply from your main electric boxes. You do not need to turn off all the power in your house, only turn off the one switch controlling the power to that hard wired smoke detector.
You can fix the 30 seconds beeping problem for your hard wired smoke detector as below:
1. Try resetting your hard wired smoke detector by locating the reset button and press holding it for about 20 seconds and then releasing it. The reset button is usually located on the front surface of your hard wired smoke detector. Wait for a minute and see if the chirping or beeping noise remains.
2. Even though your smoke detector is a hard wired one, you will be surprised it actually has a 9 volt battery connected inside the unit. This battery is a backup option in case of a loss of electric power supply. You will need to replace this 9 volt battery and the chirping will stop. This battery replacement is needed about once in a while.
3. Dust may have collected inside your hard wired smoke detector. When dust gets inside the unit, it detects the dust and sends out chirping noise or beeping noise. You will have to remove the cover of your wired smoke detector and either use Air Spray Can or vacuum cleaner hose to clean the inside of your smoke detector unit.
4. Your hard wired smoke detector is getting old and way past it's expiry date. Smoke detectors usually have a life of about 10 years. You will need a new smoke detector. It is better to buy a battery operated smoke detector than hard wired smoke detector, because it is easier to service the battery operated smoke detector unit and you don't have to deal with the wiring for a new replacement smoke detector.