5 Signs You Should Have Your Ducts Cleaned 1. You haven't changed the air filter in months. 2. The registers and vent covers have visible dust. 3. You detect mold in or around your HVAC System. 4. Airflow isn't consistent from room to room. 5. You can hear noises in the ductwork.

Boiler flues are a crucial part of your heating system. If your boiler isn't burning the gas correctly, carbon monoxide could be produced too. Boilers are made to be safe, and these gases shouldn't harm you. However, a blocked flue can mean the gases become trapped in your home, causing you to breathe them in.

In a standard-efficiency furnace, a flue pipe is attached to the heat exchanger and combustion gases exit the heat exchanger through that pipe. Newer mid-efficiency systems have a draft inducer fan that forcefully pushes combustion gases out of the heat exchanger and into the flue pipe to be exhausted out of your home.