how to tell if your furnace is leaking carbon monoxideCarbon monoxide is impossible to spot just with your eyes or nose because it is colorless and odorless. However, it’s a dangerous gas, so it is important to familiarize yourself with the signs that you have a carbon monoxide leak. If you have a gas furnace, there is always the chance that you’ll have a carbon monoxide leak. So, here is how to tell if your furnace is leaking carbon monoxide.

Carbon Monoxide Alarm

Of course, your best friend in detecting a carbon monoxide leak is a carbon monoxide detector. You should check your carbon monoxide detector’s batteries regularly. You should also ensure that you have a detector installed everywhere you need to, according to your local bylaws. This can include in front of every bedroom and near the garage.

What if your carbon monoxide alarm isn’t working? Or, you want to know if your furnace or your fireplace is the problem? There are other ways to tell if your furnace is leaking carbon monoxide. Though you shouldn’t rely on them instead of a carbon monoxide detector, it is still a good idea to know these signs so that you can help protect yourself.

Signs on the Furnace

Your furnace may give off signs that it has a carbon monoxide leak. Here are a few of them:

  • Soot: Unusual soot-like stains around the furnace may indicate that there is a carbon monoxide leak. These may be black, brown, or yellow.
  • Smells: While carbon monoxide does not create a smell, the problem that led to a leak may create a smell itself. All unusual smells should be investigated by a professional.
  • Flame: If the pilot light in your furnace is yellow instead of blue, it may be burning carbon monoxide.

Unfortunately, there are very few signs of the leak directly near the furnace.

Symptoms of Carbon Monoxide

It’s important for you to know the physical symptoms of a carbon monoxide leak that you might experience, as exposure can be deadly. Here are some possible symptoms you may suffer:

  • Dull headache
  • Dizziness
  • Weakness
  • Nausea
  • Vomiting
  • Shortness of breath
  • Chest pain
  • Blurred vision
  • Confusion
  • Loss of consciousness


Remember that the severity of these symptoms will depend on the amount of carbon monoxide you’re breathing in. However, there is no safe exposure level to carbon monoxide. If you have any of these symptoms, you should talk to your doctor.

What if You Suspect a Leak?

What should you do if you suspect a carbon monoxide leak in your home? Get your family out of the home (including pets as they can also be affected by the gas.) Call both your HVAC professional and the gas company. Large leaks may also require the fire department to respond. Then, ensure that you are your family members are all assessed by doctors to be sure that you didn’t suffer any effects from the gas exposure.

Carbon monoxide poisoning is treatable, but only when it is caught early enough. Take a moment to check your carbon monoxide alarms right now.

If your alarms are working and your furnace isn’t currently leaking, but you’re worried that it might soon, then it’s a good time to call your your local furnace repair technician. We can assess the state of your furnace and help you determine if there is a reasonable risk of carbon monoxide exposure due to faulty or unmaintained equipment.