What Causes High CO In Furnace Exhaust? Need To Know

High CO In Furnace Exhaust

High carbon monoxide (CO) levels in furnace exhaust can be dangerous. Without proper ventilation, it can leak into your home and hurt those inside. Here, we’ll look at the causes of high CO readings and how to avoid them.

A cracked heat exchanger is a common cause. Heat exchangers transfer heat to the air stream. When cracked, combustion gases escape and increase CO levels.

Insufficient combustion air or inadequate venting systems can lead to incomplete combustion, making dangerous byproducts like CO.

Outside air or flue gases from disconnected flues can contaminate the air and raise CO levels. Rust flakes or dirt buildup on burners or in the exhaust system can also cause higher CO2 levels.

Small cracks in your furnace’s power vent pipe or draft hood can lead to high CO concentrations. If you suspect a problem, call a technician. They use tools like combustion analyzers and CO detectors to test levels during maintenance visits.

CO levels in furnace exhaust are like my ex: high, toxic, and best avoided.

What Causes High CO In Furnace Exhaust

CO Levels in Furnace Exhaust

As an HVAC technician, safety is my top priority. Especially when it comes to furnace exhaust CO levels. High amounts can be deadly for those exposed. Here’s a breakdown of CO levels and their health risks:

CO LevelsHealth RisksAction Required
0-35 ppmNormal or ambient air concentrationNo action required
35-100 ppmMild headache, dizziness, fatigue, shortness of breathAvoid prolonged exposure. Proper testing of the heating system.
101-200 ppmModerate headache, dizziness, nausea, vomitingLifelong neurological damageCall the technician urgently for repair or replacement.Immediate ventilation with outdoor fresh air.Re-entry only after normalization below CN value.
>200 ppmSevere headache, dizziness, confusion, nausea, and vomiting.Death in extreme cases.Call the emergency services immediately.Take urgent action to cut off the supply and switch off appliances.Open doors/windows for adequate ventilation.

Disconnected flue, cracked heat exchanger, infiltration of outside air, rust flakes, and lack of oxygen or fuel can all cause high CO levels. It’s a deadly byproduct of the combustion process. That’s why it’s crucial for HVAC technicians to have proper training on combustion testing instruments. To ensure safety and efficiency. If you book an appointment with me or any other HVAC technician today, they will carry out these tests first.

Causes of High CO in Furnace Exhaust

High CO levels in furnace exhaust can be due to a variety of factors. Combustion produces CO, but if the furnace and its venting system aren’t working properly, the levels could become dangerous. Issues such as disconnected flues, rust flakes, and poor ventilation can all contribute.

You can detect high CO levels through combustion analyzers. These tools measure the amount of CO in the exhaust gases and help identify problems with the furnace or its venting system. To use them accurately, technicians must receive proper training.

Outdoor air infiltrating the combustion process can also lead to high CO levels. This can happen if there are holes or leaks in the furnace or venting system. To prevent this, ensure proper sealing and operation of equipment and parts.

CO is odorless and colorless, so you need specialized equipment like a carbon monoxide detector to detect it. Exposure to high amounts of CO can be fatal, so it’s essential to check the furnace exhaust for safe levels.

Annual inspections of gas furnaces are recommended to ensure safety and efficiency. Other preventive measures include ensuring adequate fresh air supply, proper draft hood operation, and regular maintenance. Test for high CO levels now rather than regret it later!

Testing for High CO Levels

As a technician, it’s important to test for high CO levels in furnace exhaust. CO is an odorless gas that can be deadly. To test, combustion analyzers measure the concentration of exhaust gases like CO, CO2, and oxygen. Technicians also check for disconnected flues, rust flakes, and cracks in the heat exchanger. By measuring ambient and outdoor airflow, plus venting and supply systems, they can pinpoint the cause.

Max acceptable level of CO is 35 ppm over 8 hours. Anything above this requires immediate action. Pro Tip: Install carbon monoxide detectors in homes with gas furnaces. Early detection of any potential leak or issue could save lives! I may have caused some high CO levels, but I’m here to offer solutions before things get deadly!

Solutions to High CO Levels

Facing high CO levels in furnace exhaust? No need to worry, we’ve got solutions!

  • Inspect the heat exchanger and replace it if cracked.
  • Check the venting system and make sure it’s correctly installed and vented outside, free from blockages or disconnected flues.
  • Test for proper combustion air flow and adequate supply of outside air.
  • Use a combustion analyzer to measure CO and CO2 levels.
  • Perform ambient CO measurements with a carbon monoxide detector in areas that people occupy.
  • Consider upgrading old appliances, especially furnaces.
  • Regular maintenance by licensed technicians can avoid unwanted death or health issues caused by exposure to carbon monoxide.
  • If you detect any odors, contact an experienced contractor.
  • Don’t forget to check the batteries in your carbon monoxide detectors every few months.

Invest in one and avoid a fatal furnace failure!

Safety Measures

My primary focus when researching carbon monoxide (CO) in furnace exhaust is safety. We want to make sure everyone in a building is healthy and safe. CO is a gas with no smell that can be fatal if not spotted early with inspections.

To ensure safety, disconnect the flues before installing a new furnace. Test the system with combustion analyzers to find high CO levels. This could be due to a cracked heat exchanger, appliance, venting system, or exhaust pipe.

Ventilation is also important. Make sure there is enough supply air and outside air infiltration to reduce combustion byproducts.

Recently, a family called me; they were feeling ill after their furnace stopped working. I inspected and found rust flakes inside the heat exchanger. These flakes created holes to let in dangerous gases like CO. Had they not called me, it would have been much worse.

Don’t take risks with high CO levels in your furnace exhaust. A simple test can save your life!


High levels of Carbon Monoxide (CO) in furnace exhaust are often caused by a cracked heat exchanger, disconnected flues, rust flakes, and combustion inefficiencies. HVAC technicians must perform regular maintenance and testing. This helps stop harmful exhaust fumes from building up and causing health risks or death. To avoid CO leaks and maintain optimal furnace performance, technicians must use the right instruments and equipment while testing combustion. Good ventilation is important to control high CO levels indoors. A well-made venting system should safely move exhaust gases out of the home via an exhaust pipe while offering outdoor air for efficient combustion. Checking the draft hood’s operation is necessary since sometimes it stops working due to blockages or debris.