filter installation

Your Furnace Filter: What It Is and How It Works

Your furnace filter is the unsung hero of your furnace. It quietly does its job without any fuss and allows the rest of the furnace to do its job. It’s not a complicated item, but there are things you need to know about it to allow it to correctly do its job.

Its Purpose

The main purpose of your furnace filter is to protect your furnace, specifically the blower fan, from all the dust, debris, hair, and other pollutants the return duct takes in. The filter also aids in your home’s IAQ (indoor air quality) for your breathing health.

How It Works

Your furnace cycles air through your Cincinnati, OH home, ducts, and furnace. The cold air is drawn through the system’s return ducts to the furnace, where the air is heated through the heat exchanger. The now-heated air travels through the ducts out through the vents into your home’s rooms. The warmer air, now in your rooms, pushes the existing cold air back through the return ducts, and the process begins again. With all this air traveling and pushing, it’s picking up the dirt, dust, and other pollutants to travel along with it. This all passes through your furnace’s filter, and the filter prevents it from getting to the rest of the system and being pushed into your rooms.

Types and Sizes


There are several types of furnace filters on the market. It can be confusing, so ask one of our Adams Heating and Cooling HVAC technicians which filter type would work best for your home and situation. The most common types are:

• Fiberglass, disposable––this fiberglass filter is typically the most common type of filter, but it only prevents the largest particles from running through your furnace. This type definitely doesn’t aid in IAQ, and if you suffer from allergies or asthma, you’d be best served by another type of filter. The fiberglass disposable type is the least expensive of all filter types and should be replaced monthly.
• Pleated, disposable––this is also a very popular type of filter, made from polyester or cotton paper. This type tends to be constructed from environmentally friendly materials and is capable of catching smaller particles like spores and mites. This filter type is very affordable and should be changed monthly.
• Electrostatic, disposable––this filter is constructed with self-charging electrostatic paper or cotton fibers that are capable of trapping potentially harmful small particles. Electrostatic filters self-charge themselves as air passes through them. This would be a good filter choice if you have pets or smokers in the home. A disposable electrostatic isn’t overly costly, but if you need a custom size, the price does increase.
• Electrostatic, permanent––this filter is also constructed with self-charging electrostatic fibers. This self-charging helps catch small particles, making it a good choice if you have pets or smokers. This permanent filter can be removed and cleaned, as it’s machine washable. There’s a higher initial cost to this one over the disposable one, but since it’s permanent, the cost evens out as it can last for up to eight or ten years when properly cleaned and maintained.
• High-efficiency pleated––this filter is made from a 4” to 5” pleated, synthetic cotton that traps the smallest particles. It’s typically attached to a metal grid that helps stop leaks. This filter is suited for you if you have autoimmune diseases or respiratory issues. Hospitals commonly use this type of filter. It is a more costly type of filter and isn’t available for all types of HVAC systems.


Just as there are different types of filters, there are different sizes as well. The size is pretty much dictated by your furnace. If you’ve noticed the measurements on your filter’s box, you’ll see it’s sized by thickness/depth, height, and length. The most common thickness is 1” and second runner up is the 4”. Common sizes range from 14” x 25” to 25” x 25”. Check your manufacturer’s instructions to determine your furnace’s recommended filter size, or, if you already have a filter, check the filter’s frame for the size printed or written there.

MERV Ratings

Filters are rated on their denseness, in terms of their Minimum Efficiency Reporting Value, or MERV. Most filters’ values range from 1 to 16, with the higher number representing the thickest and densest filter. While a filter with a higher MERV rating will most definitely catch more dust and pollutants, it can be so thick that it impedes your furnace’s airflow, which can lead to a whole other hosts of issues. It’s best to check with an HVAC technician to determine the appropriate MERV value you should use with your furnace.

Changing/Replacing It

Your furnace filter needs to replaced or cleaned on a regular basis for optimum furnace maintenance, as well as for your optimum lung health. Depending on the type of filter your furnace uses, you may need to change or clean the filter monthly or every three months at maximum. With a permanent type of filter, you may need to clean it monthly and only replace it after years of use. Since this affects the health of both your furnace and yourself, it’s best to err on the side of caution. Check your filter monthly, and if it looks dirty, replace or clean it. Those with breathing issues should definitely abide by this recommendation.

Your furnace filter is responsible for more than most people know, and its condition directly affects both your HVAC system as well as your lungs. It’s important to regularly take care of its maintenance to keep everything working well. Be sure to contact our Adams Heating and Cooling professionals at 513-474-1600 with any questions you may have about your HVAC system, especially your filter.

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“We had our complete HVAC system replaced a few weeks ago. John came to our home and gave us a full comprehensive review of all of the services and what we might be interested in -he was very non-pressure about it. Both systems installed over two days. Tommy was the lead installer -very personable and professional -covered my family room carpet with tarps and wore booties on their shoes. Was raining and AC Work got their shoes quite muddy.
All of our questions were answered and the new thermostat was explained. Eric and Dave were also involved in a recheck which was a job that completely satisfied our needs. Their clean up of the area was very comprehensive!This company I would highly recommend and have told many neighbors .”

– Jodie B.

“Our furnace died on Sunday (that snowy, cold, awful day) and we started calling furnace repair companies. Adams called back right away. Dave Smith came within one hour, diagnosed the problem, and had us warming again in a short period of time. He cleaned up after himself and it looked like he had never been there. The price was fair and we were so pleased we scheduled more work.
On Tuesday Rob Davis replaced our condensation pump. Again, Adams supplied us with a great service call in a timely fashion. Rob was very personable and talked with me about every step to make the appointment perfect.
Thank you!”

– Nicole S.

“I called Adams heating the Secretary was very nice, professional . She told me the cost for a diagnostic fee , I told her that furnace was working but it would not shut off on its own when it should. So I scheduled an appointment for one of their techs to come out and look at it. She told me the time and date , and that worked good for me. The tech came out , was verynice, polite, and professional. He told me what was wrong with the furnace, told me the cost of the part, explained to me why the furnace was not working correctly, and he got it to working right. Also told me if I had problems with the furnace to call them back, and they would come back out and fix the problem with no cost to me with I did like, because I have a small income.
I just want to thank Eric for coming out , and helping me a lot.
Thank you Eric.”

– Teresa H.

“Had an unexpected issue with my oil furnace. Via website I sent a request for service on sunday night. By 7:30 am I received a call and 2 technicians were here by 9am on Monday. Furnace was shot and needed replaced. By 10am 5 more technicians were here and 4 hrs later I had a new furnace and flue liner installed. Technicians were friendly and knowledgeable and very prompt and no mess left behind. I would recommend them highly.”

– Janet S.

“We had a furnace and air conditioner replaced. All the work was done efficiently and timely.
The service people were very knowledgeable and answered all of our questions.”

– Jerry D.

“Mike Abell was great! Mike was on time and completed all the work as quoted. Our new humidifier looks great and professionally done. I will recommend Mike and Adams Heating & Cooling to all our friends and family.”

– Chris H.

“I worked with John on the sales-side of the process and he did an outstanding job. He was thorough during the system evaluation, quoting process, and working through the execution of the purchase.

The gentlemen who installed the furnace were knowledgeable, professional, and performed high-quality work. The furnace and associated ductwork/filter cabinet is very clean with great craftsmanship.

My family and I appreciate the work performed by Adams and highly recommend!”

– Matthew H.

Adams Heating & Cooling services Anderson Township, Newtown, Milford, New Richmond, Loveland, Amelia, Eastgate, Mt Lookout, Mt Washington, Hyde Park, Indian Hill, Terrace Park, Madeira, Bethel, and the surrounding Ohio communities with their heating and cooling needs. Visit our service area page for more coverage details, call us at 513-474-1600, or request service online today.

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