Can carbon monoxide come from a furnace that is off

Q: What happens if you turn off your furnace?

A furnace can encounter problems if its turned off. These problems include the build-up of moisture which leads to rust forming. Corrosion can also happen, due to a build-up of water and soot.

Carbon monoxide poisoning is one of the major things people with gas furnaces should worry about. And when we say “major” that’s not because of the high likelihood of carbon monoxide (CO) poisoning but because of how devastating the gas’ effects can be.

Table of Contents Show

Health advisory
Key messages
What is the issue?
Who is at risk?
Recommendations
Carbon monoxide alarms
More information
How do I know if my furnace is leaking carbon monoxide?
What gives off carbon monoxide in your home?
What happens if you turn off your furnace?
What causes carbon monoxide to leak from furnace?

So, can your furnace leak the odorless and colorless carbon monoxide in your home without you realizing? Yes, it can.

Is it likely that your furnace leaks that deadly gas? If you take good care of your device, no. If you don’t take care of it – pretty much, yes.

Taking care of your gas furnace includes a series of simple but vital steps:

Perform a routine annual (preferably professional) maintenance of the unit before the start of the winter season.
Clean the furnace regularly and protect it from physical harm.
Change the air filters of the furnace often (depending on usage).
Install carbon monoxide detectors in your home.
Look out for the symptoms of monoxide poisoning such as fatigue and chest pain.

Here are a few others of the most frequently asked questions about CO leaks:

How do I know if my furnace is leaking carbon monoxide?
The easiest way to catch a carbon monoxide leak early is to have CO detectors installed in your home. If you’ve skipped that precaution, look out for soot, smoke, and fumes build-up, insufficient upward draft in the chimney, brown-yellow stains around the furnace, fires burning slower than normal, the pilot light blowing out too often, as well as physical symptoms such as chest pain and fatigue.
Can carbon monoxide leak if the furnace is off?
Technically – no. It’s the burning of a fuel that produces carbon monoxide, so if the furnace is off it won’t produce CO. However, there may be CO already distributed throughout your HVAC system which can keep leaking even after the furnace has been turned off. Plus, other fuel-burning appliances can also produce carbon monoxide while your gas furnace is off.
Can an electric furnace produce carbon monoxide?
No, carbon monoxide is produced by the burning of fuels, electric furnaces and other electric appliance don’t do that
Can a broken furnace cause carbon monoxide?
Broken furnaces are indeed the main cause of carbon monoxide leaks. That’s why routine maintenance and good care are essential – to prevent your furnace from malfunctioning.
If you mean “broken” not as malfunctioning but as “not working at all”, then – no. A non-operational furnace that doesn’t burn fuel can’t produce CO. But if your furnace burns fuel and isn’t operating at its optimal capacity, the likelihood of a CO leak should not be ignored.
Can a dirty furnace filter cause carbon monoxide?
Dirt build-up is indeed one of the main symptoms of a carbon monoxide leak. Dirty air filters, in particular, make CO leaks very likely.

Health advisory

Status:

Resolved

Advisory number:

210506

Date issued:

05 May 2021

Issued by:

Dr Angie Bone, Deputy Chief Health Officer (Environment), Victoria

Issued to:

Health professionals and the community

Key messages

Carbon monoxide is an odourless, colourless gas that may cause a range of symptoms including headache, nausea and vomiting, flushing, muscle pain, weakness, shortness of breath, dizziness, coordination difficulties, confusion, or chest pain if inhaled.
Symptoms of poisoning are non-specific and can be mistaken for a flu-like illness or even food poisoning. Very high levels of carbon monoxide can cause loss of consciousness, seizures and death.
Medical professionals are therefore requested to exercise a high level of suspicion if compatible symptoms are related to the use of gas heaters and to follow the recommendations in this Advisory.
Read the guide: Could it be carbon monoxide poisoning? to assist in the diagnosis and management of carbon monoxide poisoning.
Colder weather will increase the use of gas heaters and potentially increase the risk of carbon monoxide poisoning, where an open flued gas heater is faulty.
As any gas heater can become faulty, Energy Safe Victoria recommends all are serviced and tested at least once every two years by a licenced or registered gasfitter with an endorsement to service Type A gas appliances.
Gas heaters should not be left running continuously overnight.
Installing a carbon monoxide alarm is a useful back-up measure but does not replace the need for regular servicing of gas heaters.
Portable outdoor gas appliances should never be used indoors. Remember BBQ heat beads produce carbon monoxide and should never be used inside for cooking or heating purposes.

What is the issue?

Any gas heater has the potential to leak carbon monoxide into the indoor living area. This includes old and new heaters, central heating units, space heaters, wall furnaces and decorative appliances such as decorative log fires.

Patients may attend general practitioners or emergency departments with symptoms or concerns about carbon monoxide poisoning. As these symptoms are non-specific and frequently occur as a result of other more common conditions, it is possible carbon monoxide exposure is not considered and the patient sent home with serious or potentially fatal consequences. The source of carbon monoxide may be in the home, in the car due to a leaking exhaust system, in the workplace, or in caravans. Malfunctioning gas heating and cooking appliances are the most common sources in the home.

All gas heaters and decorative log fires need to be serviced at least every two years by a licenced or registered gasfitter with an endorsement to service Type A gas appliances. A licenced gas fitter checks the installation including testing for carbon monoxide leakage.

Open-flued gas heaters, especially models on the Energy Safe Victoria's safety alert list, may increase indoor carbon monoxide levels under certain conditions. The combination of inadequate room ventilation, and operating bathroom or kitchen exhaust fans at the same time as an open flued gas heater, may draw unsafe levels of carbon monoxide into the living area. The risk is further increased if the heater is faulty or the flue is blocked.

Who is at risk?

All people and pets are at risk of harm from carbon monoxide if exposed.

Children, pregnant women and unborn babies, older people and those with chronic illnesses are at increased risk from carbon monoxide exposure.

People may be exposed to carbon monoxide as a result of a fault or blockage of any type of gas heater or decorative log fire. This risk is reduced with regular biennial servicing.

In certain homes with an open flued gas heater, running a bathroom exhaust fan or kitchen rangehood can generate enough negative room pressure to draw exhaust gases that would otherwise rise out of the flue/chimney, into the indoor living area. Checking for this forms part of the heater’s regular service and testing. Airflow through clear wall vents or a partially opened window may prevent this from occurring.

Some specific models of open flued gas heaters are currently subject to a safety alert and must be rectified as well as serviced and tested before use.

Symptoms

Carbon monoxide is an odourless, colourless gas that may cause a range of symptoms including headache, nausea and vomiting, flushing, muscle pain, weakness, shortness of breath, dizziness, coordination difficulties, confusion, or chest pain. Symptoms are non-specific and can be mistaken for a flu-like illness or even food poisoning. Very high levels of carbon monoxide can cause loss of consciousness, seizures and death.

Anyone concerned about carbon monoxide poisoning should:

immediately turn off all gas appliances (heater, stove)
open the doors and windows to ventilate the area
leave the property, keeping the doors and windows open if possible
seek medical advice immediately or call NURSE-ON-CALL on 1300 60 60 24 (24/7). In an emergency call 000
have gas appliances urgently tested safety by a licenced or registered gasfitter with an endorsement to service Type A gas appliances.

Long-term exposure to low levels of carbon monoxide can also lead to impaired thinking and concentration, emotional lability, irritability and impulsiveness.

Diagnosis

Diagnosis can be challenging as symptoms are non-specific and occur with other more common conditions.

Health care workers should exercise a high level of suspicion if:

symptoms are temporally related with the use of a gas heater
symptoms also occur in other occupants of the household (including pets)
symptoms improve when outside the house
there are concerns about the functioning of the heater - heater appears faulty or has not been maintained/ serviced
there has been new installation of an exhaust fan or the recent blocking of wall vents.

The diagnosis of carbon monoxide poisoning is based on history and examination, in conjunction with an elevated carboxyhaemoglobin level as determined by venous blood analysis or where available a fingertip carboxyhaemoglobin monitor. Measure carboxyhaemoglobin levels in any case of suspected carbon monoxide poisoning when the patient is first seen as levels decline over time.

Seek advice from the Victorian Poisons Information Centre on 13 11 26. This is a 24/7 service that can assist in diagnosis and management of any suspected case.

Advise the patient to arrange an urgent service and test of their gas appliances before they are used again.

Advise the Environmental Health Unit, Department of Health on 1300 761 874 of all elevated results.

Recommendations

For medical professionals:

exercise a high level of suspicion if symptoms are temporally related with the use of a gas heater, occur in other occupants of the household (including pets), or the patient reports feeling better when away from their home
test for carboxyhaemoglobin levels in any person with suspected carbon monoxide poisoning
ensure the patient is aware of a possible faulty gas appliance which is urgently checked before reused
advise the Environmental Health Unit, Department of Health on 1300 761 874 of any cases of confirmed carbon monoxide poisoning in the home.

For homeowners:

Conduct regular maintenance of gas heaters (at least every two years) to reduce the possibility of carbon monoxide poisoning in the home. For more information go to Energy Safe Victoria - is your gas heater safe?

The new Residential Tenancy Regulations 2021 require rental providers to arrange gas safety checks of all gas installations and fittings in rental properties by a licensed or registered gasfitter every two years.

Gas heaters that are subject to a safety alert from Energy Safe Victoria should not be used unless these heaters have been rectified and serviced by a licenced or registered gasfitter. To view these models, go to Safety alerts - Gas open flued gas heaters.

To check whether you have an open-flued gas heater, contact the manufacturer for advice or check with your local gasfitter.

Carbon monoxide alarms

Carbon monoxide alarms can be a useful back-up precaution but should not be considered a substitute for the proper installation and maintenance of gas heating appliances. Select alarms that meet US or EU carbon monoxide standards (UL2034 (US) or EN50291 (EU), and carefully follow instructions for installation, maintenance and use.

More information

Clinical information

The department has developed a guide Could it be carbon monoxide poisoning? to assist GPs in the diagnosis and management of carbon monoxide poisoning.

For more information about diagnosing carbon monoxide poisoning - Think carbon monoxide (The Medical Journal of Australia)

Consumer information

Energy Safe Victoria: Heating your home with gas

Better Health Channel: Gas heating - health and safety issues

Department of Health - Carbon monoxide poisoning in the home

Clinicians should advise the Environmental Health Unit, Department of Health and Human Services on 1300 761 874 of any cases of confirmed carbon monoxide poisoning.

Public housing tenants with gas heating can contact the Department’s Housing hotline on 1800 148 426 for information.

Other consumers with open-flued gas heater models on the Energy Safe Victoria safety alert list need to contact the supplier (or manufacture) for servicing.

Anyone experiencing symptoms that may be due to carbon monoxide exposure should seek medical advice or call the NURSE-ON-CALL on 1300 60 60 24 (24/7). In an emergency call 000.

How do I know if my furnace is leaking carbon monoxide?

Signs of a Furnace Carbon Monoxide Leak.

Pilot Light Frequently Blowing Out..

Fallen Soot in Fireplaces..

Soot-Colored or Brown/Yellow-Colored Stains Around the Leaking Appliance..

Solid Fuel Fires Burn Lower Than Normal..

Smell of Gas (carbon monoxide is odorless, but a leakage may be accompanied by exhaust gases you can smell).

What gives off carbon monoxide in your home?

Carbon Monoxide Sources in the Home Clothes dryers. Water heaters. Furnaces or boilers. Fireplaces, both gas and wood burning.

What happens if you turn off your furnace?

A furnace can encounter problems if it's turned off. These problems include the build-up of moisture which leads to rust forming. Corrosion can also happen, due to a build-up of water and soot.

What causes carbon monoxide to leak from furnace?

The air from the furnace circulates around the outside of the heat exchanger. If there's a crack in the exchanger, the air runs across the burner and causes incomplete combustion and, in turn, creates a carbon monoxide buildup. Older appliances typically have poorer ventilation than newer units.