Furnace Warning Signs and What to Do

Know when to leave the home, when to arrange professional service and which routine care belongs in the equipment instructions. A furnace inspection or maintenance checklist is never a substitute for responding to an alarm or suspected gas leak.

If a carbon monoxide alarm sounds

1. Get everyone outdoors into fresh air immediately.
2. Call 911 from outside. Account for everyone and tell responders if anyone is missing.
3. Stay outside until emergency responders permit you to return.

Do not look for the source. If an appliance caused the alarm, keep it out of use until trained personnel have serviced it. If you suspect carbon monoxide poisoning even without an alarm, leave immediately, call emergency services and seek prompt medical care. See the CPSC carbon monoxide guidance.

If you smell or suspect a natural-gas leak

1. Leave the building and affected area immediately.
2. From a safe place away from the suspected leak, call 911, then your gas utility’s emergency line.
3. Keep others away. Return only when the emergency responders or gas utility say it is safe.

Do not investigate, attempt a repair or delay leaving to ventilate the building. In the affected area, do not use phones, operate switches or electrical equipment, smoke or use flames. A routine HVAC appointment is not the first response. DTE’s natural-gas emergency instructions explain the evacuation-first sequence; contact the utility that serves your property.

Place and test alarms using their instructions

CPSC recommends CO alarms on each level and outside sleeping areas, with batteries or backup battery power. Smoke alarms belong on each level and inside bedrooms. Follow the alarm manufacturer’s positioning instructions instead of assuming a location beside the furnace is appropriate.

Test alarms monthly and follow the manufacturer’s battery and replacement instructions. Review CPSC’s winter-heating safety guidance with your household and agree on an outdoor meeting place.

Leave cabinet, electrical and safety-device work to a professional

Do not open the furnace cabinet to test whether a door switch stops the equipment. Do not press, tape down, bypass or test an interlock or other safety device. Electrical connections, combustion components, gas piping and venting require appropriate training and equipment.

Arrange an annual professional inspection of the heating system and its venting. The CPSC indoor-air guide explains the need to inspect furnaces, flues and chimneys and follow the manufacturer’s maintenance instructions.

Keep routine filter care within the equipment instructions

A dirty or clogged filter can restrict airflow. Use the equipment and filter instructions for the correct filter, orientation, service interval and any required shutdown steps. There is no universal filter rating or change schedule suitable for every system.

Limit homeowner filter care to the safely accessible filter location and procedure identified in the instructions. If access is unclear, would require opening the equipment cabinet, or you are unsure how to proceed, leave it to a professional. Do not use a filter change as a reason to check wiring, burners or switches. The ENERGY STAR heating-and-cooling maintenance guidance explains why filter maintenance and airflow matter.

Report concerns without opening or testing the furnace

When there is no alarm, suspected gas leak or other emergency, tell a service professional what you have noticed: the room-temperature problem, unusual operating noise or repeated interruptions in heating. Report when it started and any recent service or filter change. Observations help describe the problem; they do not establish the cause.

Do not repeatedly restart equipment to see whether a problem returns, inspect a flame inside the cabinet or attempt a safety-switch test. Follow the equipment instructions and professional advice about keeping the system out of use while service is arranged. If an alarm sounds or a gas leak is suspected, use the emergency steps above immediately.