This checklist focuses on the hazards that matter most before they become emergencies.
01Moisture and Water
Foundation walls
A visual inspection of the foundation walls should happen every 6 months. Look for: white efflorescence (mineral deposits from water moving through concrete — a sign of moisture infiltration), horizontal cracks (structural concern, needs professional evaluation), and active staining or wet spots. Hairline vertical cracks in poured concrete are common and typically benign. Horizontal cracks in block foundations are not.
Sump pump
If you have a sump pump, test it annually — pour water into the pit until the float triggers the pump. Confirm the pump runs, the discharge line is clear, and water is actually moving to the exterior. A sump pump that runs but doesn't move water has a clogged discharge line. A pump that doesn't run at all has failed. Both should be addressed before the wet season.
Floor drain
The floor drain in a basement should have water in the trap. If it's dry, pour a cup of water into it. A dry trap allows sewer gases to enter the basement — a CO-adjacent hazard that most people don't consider.
02Mechanical Systems
HVAC filter
The furnace filter should be checked monthly and replaced every 1–3 months depending on filter type and household conditions. A clogged filter reduces efficiency, increases operating temperature, and can contribute to heat exchanger failure — which is a CO risk on gas furnaces.
Gas furnace and water heater
Visually inspect the flue connections on the furnace and water heater annually. Flue pipe joints that have separated or corroded allow combustion gases — including CO — to vent into the basement rather than outside. Any visible rust or separation at a joint warrants immediate attention.
Water heater
Check the temperature and pressure relief valve annually by lifting the small lever on the side of the tank — water should discharge from the pipe, then stop when you release the lever. A T&P valve that doesn't release or doesn't reseat is a replacement-level issue. A water heater without a properly functioning T&P valve is a pressure vessel without a safety mechanism.
03Electrical
Electrical panel
The electrical panel should be accessible, clearly labeled, and free of any signs of heat damage — discoloration, burn marks, or a burning smell near the panel. Breakers that trip repeatedly under normal loads are either overloaded or failing. A panel that trips frequently warrants an electrician's evaluation.
Aluminum wiring
Homes built between roughly 1965 and 1973 may have aluminum branch circuit wiring. Aluminum wiring requires specific handling at connections — standard outlets and switches are not rated for aluminum. If you're in this age range and don't know your wiring type, an electrician can verify during an inspection.
GFCI requirements
Finished basement areas require GFCI protection on outlets. Unfinished areas near utility sinks or wet locations also require GFCI. Confirm coverage and test each outlet.
04Carbon Monoxide
CO detector
A CO detector in the basement or on the floor directly above it is required if there are gas appliances in the basement. Install it at sleeping-area height — about 5 feet off the floor — not directly adjacent to the appliances, which can cause nuisance trips from normal operation.
Combustion air
Gas appliances require combustion air. A basement that has been recently weatherproofed or sealed may have reduced combustion air supply to the furnace and water heater, causing incomplete combustion and CO production. If appliances were installed or the basement was sealed after the appliances were installed, have combustion air evaluated.
05General
Egress window
A finished basement used as a sleeping area is required to have an egress window meeting minimum size requirements. If the basement has a bedroom, confirm the window meets egress standards — 5.7 square feet of opening, minimum 24 inches high and 20 inches wide, opening from the inside without special tools.
Staircase
The basement staircase should have a continuous graspable handrail on at least one side, a light switch at both the top and bottom of the stairs, and uniform riser heights (a riser that's noticeably different from the others is a trip hazard).
Every 6 months. Before and after the heating season. After any significant rain event if you have moisture history.
Ray Torres is a home safety writer based in Phoenix, Arizona. He writes about the slow, quiet hazards in residential buildings — the ones that have been sitting slightly wrong for long enough that nobody notices them anymore.