We recently replaced a unit for a customer because it was putting high levels of carbon monoxide into the home. Once the unit was removed and the heat exchanger was pulled out to inspect it further we found several large areas where it was completely rusted through. When holes or cracks develop in the heat exchanger there is a potential for carbon monoxide to enter the living space. Carbon monoxide is known as the silent killer. Luckily the customer realized there was an issue and shut the unit down until we arrived to check it out or this could have been a lot worse. This goes to show that it is very important to get your furnace checked yearly. If you have gas appliances be sure you have a working carbon monoxide alarm installed! Especially if you have an older furnace! If you have any concerns about the safety of your furnace please call us to come inspect it for you. Stay safe and remember to change your air filter!