Yes. Gas, propane, oil, and other fuel-burning furnaces can produce carbon monoxide (CO). If combustion or venting is not working safely, carbon monoxide can build up inside a home. Because CO is colorless and odorless, you cannot rely on smell to know it is present.
An electric furnace does not produce carbon monoxide through combustion, but a home with electric heat can still have CO from other fuel-burning appliances, fireplaces, generators, or vehicles.
| If a carbon monoxide alarm is sounding now
Leave the home immediately and get everyone outside into fresh air. Call 911, the fire department, or local emergency services from outside. Do not go back inside to look for the source. Do not reenter until emergency responders say it is safe. |
The U.S. Consumer Product Safety Commission (CPSC) specifically advises people not to try to locate the source of CO before leaving the property. If a malfunctioning appliance is identified as the source, it should not be used again until it has been properly serviced.
How Can a Furnace Cause a Carbon Monoxide Problem?
Carbon monoxide is created when fuel burns. A properly operating fuel-burning furnace is designed to manage combustion and vent exhaust gases safely. Problems can arise when the combustion process, venting system, or equipment is not operating as intended.
The Centers for Disease Control and Prevention (CDC) lists gas- and oil-burning furnaces among household sources of carbon monoxide and recommends annual service by a qualified technician.
Combustion problems
A fuel-burning furnace needs the correct conditions to burn fuel safely. A combustion problem can increase CO production or indicate that the furnace is not operating normally. Combustion adjustments and burner work are not homeowner troubleshooting tasks and should be left to trained professionals.
Blocked, damaged, or disconnected venting
A furnace must vent combustion gases out of the home. A blocked, corroded, damaged, loose, or disconnected flue or vent can interfere with that process. The CPSC recommends having heating systems professionally inspected each year and checking chimneys and flues for blockages, corrosion, and disconnections.
Equipment problems, including heat-exchanger concerns
Deteriorated or damaged furnace components can create safety concerns. A damaged heat exchanger is one possible issue, but it is not the only reason a furnace-related CO problem can occur. Venting, combustion, installation, and other equipment conditions can also be involved. A technician should diagnose the actual cause rather than assuming one component is responsible.
Fuel-burning furnaces vs. electric furnaces
Gas, propane, and oil furnaces involve combustion, so they can produce carbon monoxide. Electric furnaces do not burn fuel to make heat and therefore do not create CO through their normal heating process. However, a CO alarm in a home with electric heat still requires immediate attention because another appliance or source may be responsible.
What Are the Warning Signs of Carbon Monoxide?
There is no single furnace symptom that proves carbon monoxide is present. That is why a working CO alarm and the correct emergency response matter so much. Some situations, however, should never be ignored.
A carbon monoxide alarm sounds
Treat a CO alarm as a safety warning, not as a furnace troubleshooting prompt. Leave the home, call emergency services from outside, account for everyone in the household, and wait for permission before reentering.
People in the home develop possible CO symptoms
According to the CDC, common symptoms of carbon monoxide poisoning include headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion. These symptoms can resemble the flu. If CO exposure is suspected, get outside to fresh air and seek emergency or medical assistance. Do not stay inside to diagnose the furnace.
The furnace is operating abnormally
Repeated ignition problems, unusual shutdowns, visible deterioration, venting concerns, or other abnormal furnace behavior deserve professional evaluation. These symptoms do not confirm a CO leak on their own, but they are reasons not to keep resetting or experimenting with the equipment.
Can You Smell Carbon Monoxide From a Furnace?
No. Carbon monoxide itself has no color or odor. A homeowner cannot safely confirm or rule out CO by smell.
A natural-gas odor is a different warning condition. If you smell gas or suspect a gas leak, leave the property and follow the instructions of your gas utility or emergency services. Do not remain inside to troubleshoot the furnace.
What Should You Do if Your Carbon Monoxide Alarm Goes Off?
The safest response is simple: get out first. Do not silence the alarm and continue normal activities, and do not try to inspect the furnace before leaving.
- Move everyone outside to fresh air immediately.
- Call 911, the fire department, or your local emergency service from outside.
- Make sure everyone in the household is accounted for.
- Do not reenter until emergency responders have said the home is safe.
- If a furnace or other appliance is identified as a possible source, do not operate it again until trained personnel have properly inspected and serviced it.
If you are experiencing symptoms that may be related to CO exposure, the CPSC advises getting to fresh air immediately and contacting emergency services and a doctor for proper evaluation.
When Should You Call an HVAC Technician?
Emergency responders come first when a CO alarm is active or exposure is suspected. A qualified HVAC technician becomes appropriate after the immediate safety issue has been addressed, or when you have furnace or venting concerns without an active CO emergency.
Schedule professional furnace service when:
- The furnace has recurring ignition, shutdown, heating, or operating problems.
- You have concerns about the furnace vent, flue, or other exhaust components.
- The system has not had professional maintenance in the past year.
- Emergency responders, the gas utility, or another qualified professional recommends appliance inspection.
- A CO alarm event may involve a fuel-burning furnace or another HVAC-related component.
- The furnace shows visible deterioration or has a repair history that raises reliability or safety concerns.
Oasis Services provides heating and furnace repair, maintenance, and installation for homeowners in Austin, Buda, Kyle, Bastrop, and surrounding Central Texas communities. If the situation is not an active CO emergency, our team can inspect abnormal furnace operation and explain the appropriate repair or replacement options.
| Need furnace service?
If your CO alarm is not sounding and there is no immediate exposure emergency, schedule a professional heating inspection with Oasis Services. Request service online or call (512) 569-5957. |
Request Heating Service | Call (512) 569-5957
How Can You Reduce the Risk of Furnace-Related Carbon Monoxide?
Have fuel-burning heating equipment serviced regularly
The CDC recommends having gas-, oil-, or coal-burning heating systems and appliances serviced by a qualified technician every year. Regular service gives a technician a chance to evaluate operation, identify deterioration, and check safety-related components before a small problem becomes a larger one.
Maintain working carbon monoxide alarms
The CPSC recommends CO alarms on every level of the home and outside sleeping areas, following the alarm manufacturer’s installation and replacement instructions. Do not place furniture or drapes where they can block an alarm.
Keep venting systems maintained
Heating-system inspections should include the venting path where applicable. Chimneys, flues, and vent connections can develop blockages, corrosion, loose connections, or damage that needs correction by a qualified professional.
Do not ignore recurring furnace problems
A furnace that repeatedly fails to ignite, shuts down unexpectedly, or cannot heat the home consistently needs diagnosis. If your problem is that the system is running but the air stays cold, read our guide to a furnace blowing cold air for safe first checks and guidance on when to stop troubleshooting.
Furnace Safety During Central Texas Cold Snaps
Central Texas does not experience the same length of heating season as colder parts of the country, but that can make heating-system readiness easy to overlook. A furnace may sit relatively idle for months and then run heavily when a cold front arrives.
Before the next cold snap, make sure CO alarms are working, replace alarms or batteries according to manufacturer instructions, and address furnace problems before you depend on the system overnight. Homeowners who need broader heating, cooling, thermostat, or HVAC support can also review Oasis Services’ Central Texas HVAC services.
The Bottom Line
A fuel-burning furnace can be involved in a carbon monoxide problem, but you cannot reliably detect CO by smell or diagnose its source from one furnace symptom. Working carbon monoxide alarms, prompt emergency action, and professional heating-system maintenance are the safest combination.
If a CO alarm is sounding, leave the property and contact emergency services first. If the immediate safety issue has been cleared and your furnace needs inspection or repair, contact Oasis Services to schedule heating service in Central Texas.
Frequently Asked Questions
Can a gas furnace leak carbon monoxide?
A gas furnace can be associated with a carbon monoxide problem if combustion or venting is not functioning safely. If a CO alarm sounds, leave the home and contact emergency services rather than trying to inspect the furnace yourself.
Can an electric furnace produce carbon monoxide?
An electric furnace does not burn fuel, so it does not produce carbon monoxide through its normal heating process. Other fuel-burning appliances, fireplaces, generators, or vehicles can still produce CO in a home with electric heat.
Can you smell carbon monoxide from a furnace?
No. Carbon monoxide is colorless and odorless. A natural-gas smell is a separate safety warning and should also be treated seriously.
What should I do if my carbon monoxide alarm goes off?
Leave the home immediately, move everyone to fresh air, call 911 or the fire department, and do not reenter until emergency responders say it is safe. Do not remain inside to search for the source.
What are common symptoms of carbon monoxide exposure?
The CDC lists headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion among common symptoms. Suspected exposure requires fresh air and prompt emergency or medical attention.
Can a cracked furnace heat exchanger cause carbon monoxide problems?
A damaged heat exchanger can be one furnace safety concern, but it is not the only possible cause of a CO problem. Combustion, venting, installation, and other equipment conditions may also be involved. A qualified technician should diagnose the system.
How often should a furnace be checked for carbon monoxide safety?
The CDC recommends having fuel-burning heating systems and appliances serviced by a qualified technician every year. The CPSC also recommends annual professional inspection and service of heating systems.
Can I keep using my furnace after a carbon monoxide alarm?
If a malfunctioning appliance is identified as the source of CO, the CPSC says it should not be operated again until it has been properly serviced by trained personnel. An active CO alarm should be treated as an emergency, not a normal repair appointment.
