How & Where Are Vents Clogged Up on a Furnace?

Supply Vents

• An exterior air vent is necessary to bring air from the outside into the furnace. Outside your home, this vent is typically at least a foot above grade level. You can find it close to the spot inside your home where your furnace is located. A furnace usually has only one external supply vent, but several vents are inside the home to distribute the heated air. Your outside vent can become clogged with snow and debris. It should have a screen over it. And in the winter, after a heavy storm, you should check it to make sure it's free of snow.

Indoor Vents

• Indoor vents distribute heated air throughout your home. This ductwork can get get dirty and moldy. If you have pets or don't change your furnace filters often, hair and dust can accumulate in the ductwork. Mold can start to grow inside the ductwork if you have a moisture problem in your home. Insects can get into your ductwork, and in a worst-case scenario, vermin can take up housekeeping and even die in the ductwork. This not only can cause a blockage, but also can create a very bad smell.

Filters

• The filter is typically located close to or inside the furnace, where the blower channels air out of the heating system. Filters are designed to catch air particles, and if they're not changed frequently, they can become clogged. Filters should be cleaned or replaced -- depending on the type of filter you have -- at least every several months. Some should be changed more frequently. If you are unsure about how often your filter should be replaced, consult the owner's manual for your furnace. In addition, familiarize yourself with MERV -- minimum efficiency reporting value -- ratings, and purchase one that's best for your heating system. The right MERV filter can do the best job of trapping air particles and keeping all of your heating-system parts clean.

Vent Attachment

• Dust, dirt or critters in your ductwork may not be the culprits if you're having an airflow problem. Dented or crushed ductwork can block airflow. Check the registers in all of your rooms. Furniture may be in in front of one or more air vents, and this, too, can block airflow. Check all of the visible ductwork in your home, making sure it's damage-free, and move any furniture that's blocking your vents . While you're at it, check the ductwork for leaks. Ductwork that isn't sealed properly can leak your warm air. If you suspect that you have a serious problem with your ductwork, call an HVAC-system contractor with expertise in ductwork.