5 Signs It’s Time to Call for HVAC Repair

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You might expect the five signs that you need HVAC repair to be things like, reduced effectiveness of the heating or cooling, or frequent cycling, or error codes, but this blog is not about those heating system signs, it’s about the real environmental signs. Carbon monoxide (CO) is a colorless, odorless gas that can accumulate silently in your home due to malfunctioning or poorly maintained heating systems. While people often think of CO exposure in terms of health symptoms alone, there are multiple indicators—human, animal, environmental, and mechanical—that could point to a serious issue. Recognizing these early warning signs might not only save your HVAC system, but could save lives.

So, because of the reason of carbon monoxide showing up where it shouldn’t, here are five signs it’s time to call a licensed HVAC professional for repair:

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1. Unexplained Physical Symptoms in People

Feeling off at home—but better when you leave? It could be more than a coincidence. Early signs of carbon monoxide exposure in humans include:

  • Headaches
  • Dizziness or lightheadedness
  • Nausea or vomiting
  • Shortness of breath
  • Fatigue or weakness

These symptoms can mimic the flu or general exhaustion but typically improve when you’re away from the home, and can be an important clue that something’s wrong with your indoor air.

2. Odd Behaviour or Illness in Pets

Pets are often the first to react to CO leaks due to their small size and faster breathing rates. Watch for:

  • Irritable or anxious behaviour
  • Refusal to enter the house after being outdoors
  • Vomiting or loss of coordination
  • Drowsiness or trouble breathing
  • Bright red gums, ears, or lips

If your dog or cat is acting strangely or seems unwell without a clear cause, don’t overlook the possibility that your heating system may be at fault.

3. Dying Houseplants Without Explanation

Healthy indoor plants can be surprisingly sensitive to changes in air quality. If your houseplants are:

  • Wilting unexpectedly
  • Turning yellow or dropping leaves
  • Dying suddenly despite proper care

…it could indicate that carbon monoxide is displacing the oxygen in your home, creating an environment where even resilient plants can’t survive.

4. Condensation on Windows Near Heating Appliances

Excess moisture on windows or walls—especially near furnaces, boilers, or water heaters—can be a sign that combustion gases aren’t venting properly. When flue gases back up into the home, they often bring water vapor with them, leading to:

  • Persistent fogging on windows
  • Damp walls
  • Visible moisture near vents or exhaust outlets

This kind of condensation isn’t just annoying.  At best, it could indicate an air flow issue.  At worst, it could be a symptom of carbon monoxide entering your home.

5. Soot, Pilot Light Changes, or Appliance Shut-Downs

Visual signs around your appliances can also alert you to a dangerous condition. Watch for:

  • Excessive soot or dark staining on walls, ceilings, or around the appliance
  • Pilot lights that burn yellow or go out frequently (they should be blue and steady)
  • Appliances shutting off unexpectedly or not staying lit

These signs often point to incomplete combustion or improper venting, both of which can result in carbon monoxide leaks.

A Real Story: What a “Routine Service” Revealed

We were recently called to perform a standard maintenance service on a home’s boiler and hot water tank. During the initial inspection we uncovered a serious issue: the horizontal vent pipe that connected the heating appliances to the chimney was severely corroded, with large holes. That’s the lead picture on this blog.  

The problem? A long horizontal exhaust run caused the toxic gases to cool before reaching the chimney. This led to condensation inside the pipe. Over time, that condensation— highly acidic in nature—ate through the galvanized metal, creating gaps where carbon monoxide could escape directly into the ambient air inside the home.

This wasn’t just a maintenance issue—it was a life safety risk.

Crawl spaces, like the one in this home, can have these problems.  The location of the heating and water heating appliances may be located close to the access door for ease of installation and maintenance but the chimney where these appliances are often exhausted, might be on the opposite wall.  Poor access, low light and tight conditions may make it difficult for homeowners to see or notice issues themselves. That’s why regular inspections by licensed HVAC professionals are essential, especially when heating or hot water systems are installed in out-of-sight locations.

Don’t Wait Until It’s Too Late

Carbon monoxide gives no warning until it’s already affecting your health. Carbon monoxide is also the same density as air so it won’t raise up or sink to the floor.  Carbon monoxide detectors can be ineffective at low levels if not installed in the right locations.  If you suspect carbon monoxide has become an issue in your home, take action:  

  • Leave the home immediately
  • Call 911 or your local emergency services for health related intervention
  • Schedule a professional HVAC inspection with a licensed contractor and be sure to let them know why!  
  • Install carbon monoxide detectors on every floor of your home in accordance with the best standards.  

Routine maintenance isn’t just about comfort—it’s about safety. If it’s been more than a year since your last heating system inspection, now is the time to make the call.    

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