Chapter 1 — What You’re Actually Solving

Detector upgrades / replacements are one of the simplest electrical jobs and one of the most important. Your situation is probably:

• Beeping detector — 10-year end-of-life alarm. Replace all on the interconnect chain at once.
• Expired detector (manufactured date > 10 years ago). Replace.
• Battery-only upgrade to hardwired — more involved; requires running cable.
• New-construction spec — builder delivered minimum; you want better.

The replacement job takes 20 minutes per detector once you’ve got the first one done.

Code requirements (typical)

• Every bedroom.
• Outside every sleeping area (hallway).
• Every floor of the home including basement.
• Every attached garage.
• Every 10–12 feet along a hallway.
• CO detectors on every floor with a sleeping area (most states).

Hardwired on new construction after 1994 in most jurisdictions. Older homes are grandfathered but replacements are a chance to upgrade.