Smoke Alarms and CO2 Detectors: Battery or Hardwired?
Smoke alarms don't just save lives. They're also legally required in many parts of the country. Furthermore, newer homes might need to have hardwired smoke detectors. While hardwired smoke detectors still have a battery backup, they're connected directly to the house's main electrical system, meaning that, as long as you have power, they'll work even if you forget to change the batteries.
Battery vs. Hardwired
Homes built before 1992 generally aren't required to have hardwired smoke detectors. However, they still need to have smoke detectors installed, although battery-powered ones are adequate. Homes built in California after 1992 must have hardwired smoke detectors that also have a battery backup. This law also applies to homes built before 1992 that have been through major renovation projects.
Smoke Detector Locations
One smoke detector probably won't be enough to meet local ordinances, either. Generally, a dwelling needs smoke detectors outside of any area with bedrooms. If your house has two wings or has two floors with bedrooms, you'll need two smoke detectors. If the house was constructed after 1992, a smoke detector is required in each bedroom, and the smoke detectors must be hardwired.
Enforcement
When you own a house, you probably don't have to worry about a fire marshal coming into your home and inspecting it. However, when you sell your house, you will have to bring it into compliance with the laws for the number, location and installation type of smoke alarm. When you own a rental property or duplex, it's your responsibility to maintain operating smoke detectors that meet the law's requirements at all times.
Carbon Monoxide Detectors
Hardwired smoke detectors aren't enough, though. Since 2011, California homes that have anything that burns -- like a gas furnace, wood-burning fireplace, pellet stove or propane cooktop -- also need to have carbon monoxide detectors. The CO detectors need to be in any area with bedrooms and need to be hardwired in homes built after Jan. 1, 2011. Homes built before that date can have battery-powered detectors.