No equipment response
Thermostat, power, controls and safety states remain different possibilities.
Notice next: Record display and model-manual indicators without opening equipment.
United States guidance50 states + DC context
Loss of home heat
Reviewed and updated September 21, 2026
What should you do when the furnace is not heating?
Put safety before diagnosisCO, suspected fuel gas, fire, electrical warning and dangerous cold come before any attempt to restore heat.
Leave for fresh air and call emergency help for a sounding carbon-monoxide alarm or suspected CO symptoms. If you suspect a gas leak, leave without operating switches or creating an ignition source and contact the gas emergency authority from a safe location. Smoke, flame, burning odor, sparks, shock or repeated breaker trips also stop checks. During dangerous cold, protect occupants and use only safe, approved temporary-warmth guidance.
After those gates are clear, identify whether the system is gas, oil, electric or a heat pump; record thermostat display/mode/setpoint, whether equipment starts, filter condition, open vents and any exact owner-manual code. Do not relight a pilot, manipulate fuel valves, bypass a safety switch, repeatedly reset power or open panels based on generic instructions. The same no-heat symptom can require different model-aware diagnosis.
Separate life safety, system behavior and comfort symptoms
Which situation best matches the home?
Air moves but is not warm
Fuel/system type, operating stage and equipment state matter; airflow alone does not identify the cause.
Notice next: Note timing, mode and whether the system shuts down or repeats.
System starts and stops or shows a code
A repeated shutdown may be protective and should not be defeated.
Notice next: Copy the exact code and stop repeated resets.
Safe observation
What should you record before the call?
A short, factual description helps the next professional choose the right first inspection without treating a symptom as proof.
Basic observations do not diagnose ignition, fuel, heat exchanger, electrical, control, blower or heat-pump faults and do not authorize internal work.
What to record
- System type, fuel/energy source, brand/model and safely visible code.
- Thermostat display, mode, setpoint and call indication.
- Equipment start, fan operation, filter and open vent observations.
- CO alarm/symptoms, gas odor, smoke, flame, electrical warning and repeated trips.
- Indoor temperature trend and people at risk from cold.
Stop and get appropriate help
- A CO alarm sounds, people have possible CO symptoms or fuel gas is suspected.
- There is smoke, flame, burning odor, sparks, shock or repeated breaker trip.
- Indoor cold creates an urgent risk or safe temporary heat is unavailable.
Short answers
Questions people ask before the call
Should I relight the pilot myself?
This national guide does not give a universal relight procedure; fuel controls and model instructions differ, and any gas concern is a leave-and-call boundary.
Can I use the oven to heat the home?
No. Use only temporary-heating methods approved for the space and follow fire and CO safety guidance.
Does cold air prove the furnace burner failed?
No. The system type, timing, controls and equipment state need proper evaluation.
Where this guidance applies
The safety and observation sequence on this page is general U.S. guidance.
Emergency resources, adopted mechanical and electrical codes, permits, contractor licensing, climate loads, utility programs, prices and provider availability must be checked for the exact property.
A ZIP helps identify possible HVAC service areas and utility territories, but it does not prove jurisdiction, address-level coverage or an available qualified HVAC technician.
Sources and boundaries
What supports this guide?
- National Fire Protection Association — NFPA Educational Messages 2026 Edition Desk Reference for the Fire Service and Fire and Life Safety EducatorsStandards-owner consumer messages for CO alarm response, fresh-air and 911 escalation, annual fuel-burning-equipment inspection and fuel-gas emergency actions. Scope: national. Source checked 2026-09-16.
- National Fire Protection Association — Heating SafetyStandards-owner heating-safety boundary to leave immediately and call the fire department or gas company when gas is smelled at a gas heater. Scope: national. Source checked 2026-09-16.
- NOAA National Weather Service — During Extremely Cold WeatherNational cold-exposure, frostbite, hypothermia and safe power-outage warmth guidance when home heat is unavailable. Scope: national. Source checked 2026-09-16.
- U.S. Fire Administration — Heating Fire SafetyFire-safety boundaries for heating equipment and temporary heat without authorizing repair steps. Scope: national. Source checked 2026-09-16.
- U.S. Department of Energy — Consumer Guide to Home Heating and CoolingNational system-type, maintenance, filter, duct, thermostat and owner-manual context without fault diagnosis. Scope: national. Source checked 2026-09-16.
Educational information only: this page cannot inspect the property, diagnose hidden work, provide legal advice, quote a repair or promise service availability.
Sources support the general guidance shown here. Address-specific rules, responsibility, price and availability still require current local confirmation.
If conditions are unsafe or rapidly worsening, stop troubleshooting and contact the appropriate emergency service or qualified local professional.