Can An Oil Furnace Cause Carbon Monoxide Poisoning?

Carbon monoxide (CO) is a poisonous, odourless, and colourless gas that may build up in a home with an oil furnace, resulting in dangerous levels in the air—it can even be deadly if enough of the gas accumulates in your home. 

The risks and dangers of carbon monoxide poisoning are real, meaning you should take steps to reduce your chances of being exposed to too much CO from your oil furnace. The health and safety of you and your family depends on it! 

This blog will walk you through how oil furnace carbon monoxide leaks happen, the warning signs, and explain how preventative furnace maintenance can help. 

💡 Read more: The Ultimate Guide to Buying a Furnace for Homeowners

Oil Furnace Carbon Monoxide Poisoning Explained 

Like other fuel-burning appliances—including boilers, gas stoves, and heaters—an oil furnace can produce dangerous levels of CO. It happens when the furnace is not vented correctly, when it’s burning fuel inefficiently, or when the burner becomes clogged.

Some carbon monoxide from your furnace is normal, as all appliances that burn fossil fuels produce a small amount of CO as a byproduct. This is expected and is not dangerous if the appliance is functioning normally.

However, oil furnace carbon monoxide poisoning occurs when the levels of CO in your home get too high, especially if it’s contained in a small area. In these cases, CO can quickly reach dangerous levels and cause symptoms of carbon monoxide poisoning.

The Canadian Hospital’s Injury Reporting Prevention Program (CHIRPP) recorded around 767 unintentional CO-related events between 2011 and 2023. Most happened during the cold seasons, with furnaces ranking as the fourth leading cause.

There are several reasons for this, which include:

• Improperly installed and unmaintained furnaces
• Wrong furnace size
• Blocked ventilation systems 
• Heating system malfunctions (i.e. cracked heat exchanger and exhaust pipes)
• Age of furnace

Symptoms of Carbon Monoxide Poisoning 

In general, the maximum indoor safe CO level is 9 ppm over eight hours. 

Given how CO is a colourless and odourless gas, installing a carbon monoxide detector is the best way to monitor levels. There should be CO detectors on every floor of your home—including the basement—located within 10 feet of each bedroom.

Elevated levels of carbon monoxide from furnaces can lead to poisoning and the following symptoms:

• Headaches
• Dizziness
• Nausea
• Confusion
• Fainting
• Shortness of breath
• Fatigue
  

In extreme cases, prolonged exposure at high concentrations can result in death. 

How to Spot a Carbon Monoxide Leak 

The key to preventing carbon monoxide leaks is being proactive. The warning signs indicating that your furnace may be leaking include: 

• Soot or stain around the vent pipe on the outside of your home
• A yellow flame burning inside your oil furnace (instead of a blue one)
• The pilot light frequently blows out
• Excess moisture on walls and windows near the oil furnace
• Pets suddenly falling ill
• An increase in headaches, nausea, dizziness, confusion, and fatigue (especially if they disappear after you leave your property)

As soon as you observe any of these signs, get your oil furnace inspected for carbon monoxide emissions by a qualified technician. 

Can Carbon Monoxide Come From a Furnace That Is Off? 

Technically, your unit won’t produce carbon monoxide if it’s off. 

However, your oil furnace may pull in some CO from other sources in your home like your water heater or gas appliances. This residual CO circulates throughout your house, especially if you have holes in your air ducts. It can then be distributed through your furnace ducts even if the leaks come from outside your system. 

So, no matter how well you maintain your furnace, there is still a risk if you have other sources of carbon monoxide in your home. Always check your appliances regularly to ensure they are functioning correctly and seal any air ducts that may be leaking.

Don’t Forget Your HVAC System 

Your HVAC system is also at risk of CO leaks if it’s not maintained properly. Though modern systems have safety features to shut off the system if CO levels become too high, these will only work correctly if the system is regularly checked and maintained.

Regular maintenance is critical in preventing furnace carbon monoxide poisoning, and this job requires the attention of professionals. Licensed HVAC technicians are experts in diagnosing and repairing potential issues in your heating and cooling systems. They’ll effectively clean vents, replace broken parts, and fix faulty wirings. 

DIY furnace repair is a bad idea, as it often creates new problems or worsens existing ones. However, you can do your part by keeping the area around your furnace clean, replacing air filters regularly, and keeping your eyes and ears open for signs of a furnace leak.

💡 Read more: The Ultimate Seasonal HVAC Maintenance Guide for Homeowners

Tips to Prevent Carbon Monoxide Leaks 

You can prevent carbon monoxide poisoning by taking a few simple steps.

• Have your furnace, boiler, and water heater serviced regularly by a qualified technician. While you can physically check your appliances for any visible damage, only a qualified technician can ensure that your furnace is burning fuel efficiently. They have the knowledge, tools, and experience to detect and repair any underlying issues.
• Install carbon monoxide detectors in your home. Choose a detector that is certified for its smell, accuracy, and sensitivity. Replace your carbon monoxide alarm every five to six years or as specified by the manufacturer.
• See to it that your air vents are clear and not blocked. Check your vents and the area around them for any blockage or debris. If you find anything that might be blocking airflow, carefully remove it or contact a qualified technician to do this.
• Check your chimney regularly. It should be clean and free of creosote buildup, and the flue should be open. If you have a gas-fired furnace, check all your connections to ensure they are secure and there are no leaks.
• Replace old appliances with newer, energy-efficient models. Newer furnaces and appliances are built with better combustion technologies that produce less CO. On average, you should replace them every ten years as they become less efficient.

Prepare For the Winter with Professional Furnace Maintenance 

Installing carbon monoxide detectors is a great start, but the best way to avoid dangerous CO leaks is with regular maintenance from LG Home Comfort. 

Our licensed technicians are available around the clock to inspect your oil furnace and make sure everything is running right. However, if you do encounter a potential leak, we’re only a call away to get the problem resolved quickly. 

An oil furnace carbon monoxide leak is no joke—be proactive by scheduling a maintenance visit today.