Can a Blocked Filter Make a Furnace Leak?

Cause and Effect

• Carbon monoxide can only enter the occupied parts of a building if there has been a physical failure in the furnace; the heat exchanger must have cracked, which most frequently happens as a result of too-rapid cycling on and off of the flame. Peak-and-trough heating and cooling can split welds, through which combustion gasses escape. This can be a direct result of a dirty filter.

  A dirty filter obstructs the necessary air flow around and through the heat exchanger, which causes overheating. Overheating warps the metal, and welds crack. Once such damage has been sustained, the heat exchanger cannot be repaired; the system must not be used again until a replacement component has been installed.

Carbon Monoxide Poisoning

• Natural gas and propane are both carbon-based fuels, and as such give off carbon monoxide when they burn. Carbon monoxide is both without color and without odor, and can very quickly cause death by asphyxiation. Initial symptoms include a sleepy feeling accompanied by trouble concentrating and dizziness. If you experience any of these symptoms, get into the fresh air quickly then call a certified technician to diagnose the problem. Fit carbon monoxide detectors in your home.

Further Problems

• If the furnace is part of a heating, ventilation and air conditioning system, a blocked filter can cause other problems even in hot weather. Reduced air flow can result in the air conditioner coil icing over, which in turn can lead to ruptures in the system and a Freon leak. While Freon is not a hazard to health as is carbon monoxide, the leak will require a service visit and probably a costly repair.

  Another non-lethal but still serious issue is that blocked filters can increase your utility bill. As Alpine Home Air Products in Illinois observes, “When filters become clogged with dirt, the system must work harder to do its job.”

Other System Filtration

• Some floor registers are marketed with integral filters. If these are blocked, the effect can be the same as a blocked inlet filter; air cannot move freely through the system and identical problems can result.