1. Absence of a Carbon Monoxide Detector: If you don’t have a functioning carbon monoxide detector installed in your home, it increases the risk of not being alerted to a CO leak.

2. Malfunctioning or Expired CO Detectors: If your carbon monoxide detectors are not working correctly or have expired batteries, they may fail to detect CO leaks. Regularly test and replace batteries according to manufacturer guidelines.

3. Yellow or Flickering Gas Burner Flame: A gas burner flame should burn blue. If you notice a yellow or flickering flame, it could indicate incomplete combustion and the potential presence of carbon monoxide.

4. Soot or Stains Around Appliances: Accumulation of soot or black stains around gas appliances, heating systems, or chimney flues can signify incomplete combustion and a possible carbon monoxide problem.

5. Excessive Condensation on Windows: If there is unusual and persistent condensation on the interior surface of your windows, it could indicate high humidity levels resulting from improper ventilation caused by a CO leak.

6. Stale, Musty, or Unusual Odors: Carbon monoxide is odorless, but other byproducts of combustion might produce stale, musty, or unusual smells. If you notice persistent odors, especially near fuel-burning appliances, it’s worth investigating further.

7. Headaches, Dizziness, Nausea, or Fatigue: Carbon monoxide poisoning symptoms often resemble flu-like symptoms, including headaches, dizziness, nausea, or fatigue. If these symptoms improve when you leave your home and reappear upon returning, it may indicate a CO leak.

8. Increased Incidents of Illness in Household Members or Pets: If multiple household members or pets experience unexplained and recurrent flu-like symptoms, it could be a result of carbon monoxide exposure. Pay attention to patterns and consult a medical professional if needed.