Furnace heat exchanger cracks and carbon monoxide risk

What the safety sources say about the heat exchanger

In plain words, the heat exchanger is the furnace part that sits between the burning fuel and the air in your home. The government pages we read do not define it, but they do show where the part sits in the safety picture. Flue gases are the exhaust that comes from burning fuel.

The Environmental Protection Agency (EPA) lists gases and particles from burning fuel (called combustion) that come from chimneys and flues that are improperly installed or maintained, and from cracked furnace heat exchangers. A federal recall notice says a separated heat exchanger tube could leak flue gases, including carbon monoxide.

The ENERGY STAR maintenance checklist says a dirty burner or a cracked heat exchanger causes improper burner operation. It places the heat exchanger among the items a heating check should cover.

What carbon monoxide is

Carbon monoxide, written CO, is a colorless, practically odorless, and tasteless gas, according to the EPA. The EPA says it comes from incomplete burning of carbon-containing fuel. In plain words, the fuel burns without enough oxygen to burn fully.

The Centers for Disease Control and Prevention (CDC) calls CO an invisible, odorless, poison gas that kills without warning. It also says that gas- and oil-burning furnaces produce carbon monoxide, along with portable generators and charcoal grills.

How heat exchanger cracks can form

The sources we read point to two routes. None is a full engineering explanation, and we do not add one.

The first route is overheating. A 2004 recall notice from the Consumer Product Safety Commission (CPSC) for York's gas furnaces, under the Coleman, Coleman Evcon and Red T names, says these furnaces can overheat, causing heat-exchanger cracking. A 2012 CPSC notice about a fire hazard says an overheated furnace can crack the heat exchanger and create openings.

The second route is a failed weld. An older federal warning about certain oil and wood combination furnaces cited a pattern of weld failure that could allow carbon monoxide to escape and be drawn into the home.

Corrosion is a separate concern, and the sources do not tie it to cracking. The EPA says proper maintenance is important even for new furnaces, because they can also corrode and leak combustion gases, including carbon monoxide.

These recalls covered specific products and are dated. They show how cracks have been described, not how common they are today.

Why a cracked exchanger can put carbon monoxide in the home

The CPSC says that under certain conditions, all appliances that burn fuels can leak deadly levels of CO into the home. It also says improvements in modern furnaces do not protect against all conditions that can lead to CO exposure.

In another release, the CPSC says heating systems can cause CO poisoning if they are improperly installed, poorly maintained, have defective or blocked venting systems or are misused. Venting systems are the pipes and chimneys that carry exhaust gases out of the home. The EPA adds that worn or poorly adjusted and maintained combustion devices can be significant sources.

The takeaway is not that every furnace will crack. It is that the agencies treat the heat exchanger as a part that deserves a trained look every year.

Symptoms and what to do

The sources we read give no sign a homeowner can use to tell that a heat exchanger is cracked. They do list symptoms of CO poisoning.

The CDC says the most common symptoms are headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion. It adds that people who are sleeping, drunk, or under the influence of other substances can die from CO poisoning before they have symptoms.

If you have symptoms you think could be from CO poisoning, the EPA says to get to fresh air immediately and seek medical attention. The CPSC says to get outside to fresh air immediately and then leave the home and call your fire department, because you could lose consciousness and die if you stay in the home. If a doctor confirms CO poisoning, the CPSC says a qualified service person should check the appliances before they are used again.

If a CO alarm sounds, the CPSC says not to try to find the source of the CO. Move outside to fresh air, then call emergency services, the fire department, or 911. Do not go back in until emergency responders give you permission.

The CDC also says to install battery-operated or battery back-up CO detectors near every sleeping area in your home. The EPA says to test alarms once a month. For placement, see carbon monoxide detector placement.

Yearly service and Florida alarm rules

The CDC says: "Have your heating system, water heater, and any other gas, oil, or coal burning appliances serviced by a qualified technician every year." See what a heating tune-up covers for that visit.

A federal technical brief is written for crews doing weatherization, which is work that makes homes more energy efficient. It says that if cracks or holes are found, the heat exchanger is replaced if a new one can be found, or the unit is referred for replacement. That is a procedure for trained crews, not a homeowner task.

Florida Statutes section 553.885 covers every separate building, or addition to an existing building, constructed on or after July 1, 2008. It applies if the building has a fossil-fuel-burning heater or appliance, a fireplace, an attached garage, or another feature that gives off carbon monoxide when fuel burns. Such a building shall have an approved operational carbon monoxide alarm installed within 10 feet of each room used for sleeping purposes. The statute as we read it does not cover every existing home.

If you are weighing a gas furnace against electric heat, see gas furnace versus electric heat.