Two technologies do more to prevent electrical injuries and fires in residential buildings than anything else the NEC requires: ground-fault circuit interrupters (GFCI) and arc-fault circuit interrupters (AFCI). If your Denver home was built or renovated in the last five to ten years, you probably have them in the right places. If it predates the mid-2000s and has never been updated, it almost certainly does not.
The distinction matters because GFCI and AFCI protect against different hazards. GFCI detects when current is flowing somewhere it should not — through a person, through water, through a ground fault — and interrupts the circuit within 25 milliseconds, fast enough to prevent electrocution. AFCI detects the electrical signature of an arcing fault — a loose connection, a damaged cord, a staple driven through a wire — that creates intermittent sparking that can ignite insulation.
GFCI requirements by room (2023 NEC)
Kitchens: all outlets serving the countertop must be GFCI-protected, including small appliance circuits. Bathrooms: all outlets. Garages: all 120V outlets. Outdoors: all 15A and 20A outlets. Unfinished basements: all 15A and 20A outlets. Crawl spaces: all outlets. Within 6 feet of a sink in any room: any 15A or 20A outlet. Laundry rooms: the outlet serving the washing machine. Near boilers and HVAC equipment in unfinished spaces.
AFCI requirements by room (2023 NEC for new construction; Colorado has adopted the 2020 NEC with Denver amendments): bedrooms — this is where AFCI started, and the original requirement has been in effect since NEC 2002 in many jurisdictions. Living rooms, family rooms, parlors, libraries, dens. Hallways and stairways. Sunrooms and closets. Dining rooms and kitchens (as of 2014 NEC). Laundry rooms.
What older Denver homes are missing
A home from the 1990s in Park Hill or Globeville likely has GFCI in the kitchen and bathrooms — that requirement is older. What it probably lacks is AFCI protection on bedroom and living room circuits, GFCI in the garage, and GFCI within 6 feet of the laundry sink. None of that is grandfathered as acceptable — existing violations do not become code-compliant simply because the home was built before the requirement. They only become enforcement issues during a permit inspection or when a home is sold.
Upgrading individual outlets to GFCI runs $80–$150 per location including labor. Replacing a standard breaker with a combination AFCI/GFCI breaker (which protects the entire circuit) runs $120–$250. A full compliance audit of a typical Denver home takes two to three hours and produces a written list of every location that needs attention — something many homeowners find useful before listing a property.