If your furnace filter seems to get dirty much faster than it should, there is usually a reason.
A furnace filter is designed to capture dust, pet hair, pollen and other airborne particles before they circulate through your heating and cooling system. Some buildup is normal. But if the filter becomes heavily coated after only a few weeks, your furnace may be pulling an unusually large amount of debris through the return air system.
Several common problems can cause this.
You have more dust in your home than usual
The more dust that is floating through your home, the faster your furnace filter will collect it.
This can happen after remodeling, drywall work, sanding, flooring installation or other projects that produce fine dust. Even moving furniture, cleaning out a basement or doing major household cleaning can temporarily increase the amount of debris in the air. If you recently completed work inside your home, you may need to replace your furnace filter more frequently for a while.
You have pets
Dogs and cats can add a surprising amount of hair and dander to the air. Homes with multiple pets often go through furnace filters faster than homes without pets, especially during periods when animals are shedding heavily. If you have pets and your filter is getting dirty quickly, that does not necessarily mean something is wrong with your furnace. It may simply mean the filter is doing its job.
Your furnace is running more often
Your furnace filter only collects debris when air is moving through the system.
During very cold weather, your furnace may run much longer than it does during milder conditions. More operating time means more air passes through the filter, which means the filter can become dirty faster. This is one reason a filter that lasts several months during one part of the year may need to be changed much sooner during the heating season.
Your blower fan is running continuously
Many thermostats allow you to set the furnace fan to either AUTO or ON.
When the fan is set to AUTO, the blower normally operates when the furnace or air conditioner is running. When the fan is set to ON, the blower may run continuously, even when the furnace is not heating your home. Continuous airflow can improve air circulation, but it also means your furnace filter is constantly filtering air. That can cause it to become dirty much faster. Check your thermostat if you are suddenly going through filters faster than usual.
The filter may be too restrictive
Not all furnace filters are the same.
Some high-efficiency filters are designed to capture very small airborne particles. While that can improve filtration, a very restrictive filter can also accumulate debris quickly and reduce airflow if your heating system was not designed to use it. Higher filtration is not always better for every furnace. Your HVAC technician can help determine which filter size and filtration level are appropriate for your particular system.
Your return air ducts may be pulling in dust
Your furnace draws air back into the system through return air ducts.
If those ducts have gaps, loose connections or openings in dusty areas such as an attic, basement, crawlspace or utility room, the system may pull additional dust and debris into the furnace. That extra material eventually ends up on the filter. If your filters suddenly started getting much dirtier than they used to, a problem with the return ductwork may be worth investigating.
Construction or renovation can clog filters very quickly
Home improvement work is one of the fastest ways to ruin a furnace filter.
Drywall dust, sawdust and other fine construction particles can spread throughout a house and quickly become trapped in the HVAC system. If you are remodeling, check your furnace filter frequently during the project and again after the work is finished. In some cases, a filter may need to be replaced several times during a major renovation.
Using the wrong size filter can cause problems
Your furnace filter should fit properly inside the filter rack.
If the filter is too small, air can travel around the edges instead of through the filter. This allows dust to enter the furnace and ductwork. A badly fitting filter can also create unusual airflow patterns that cause debris to accumulate unevenly. Always use the filter size recommended for your system.
How often should you check your furnace filter?
There is no single replacement schedule that works for every home.
Your filter may need attention more often if you have:
Several pets
Smokers in the home
Recent construction or remodeling
Family members with allergies
A continuously running blower fan
Heavy furnace or air conditioner use
A particularly dusty home
Rather than relying only on the replacement interval printed on the filter packaging, inspect the filter regularly. If it is visibly coated with dust and debris, replace it.
Can a dirty furnace filter cause problems?
Yes.
A heavily clogged filter restricts airflow through your heating system. Your furnace needs proper airflow to operate correctly. Restricted airflow can cause the furnace to work harder, reduce heating performance and contribute to overheating problems. In some situations, a furnace may shut itself down because it becomes too hot. Replacing a dirty filter is one of the simplest things you can do to help your furnace operate properly.
What if my furnace filters suddenly started getting dirty faster?
A gradual difference may simply be related to pets, weather or increased furnace use. A sudden change deserves more attention. If the same type of filter used to last several months but is now becoming extremely dirty within a few weeks, something may have changed inside your home or HVAC system. Check for obvious causes such as remodeling work, a thermostat fan setting that was changed to ON or unusual amounts of household dust. If you cannot find an explanation, your furnace and ductwork may need to be inspected.
Need help with your furnace?
A dirty furnace filter does not always mean your furnace needs repair, but filters that become unusually dirty can sometimes point to airflow, ductwork or equipment problems.
If your furnace is not heating properly, is running constantly, is overheating or is going through filters much faster than normal, Roberts Brothers Comfort can inspect the system and determine what is causing the problem. We provide expert furnace repair service throughout Ohio’s Miami Valley region including Casstown, Covington, Fletcher, Piqua, Rosewood, Saint Paris, Sidney, Tipp City, Troy, Urbana, West Milton and all the surrounding areas.
