Pollutants in your home can include mold spores, dust mites, pet dander, cigarette smoke, and pollen, among other things. These pollutants are invisible to the naked eye but can cause health problems like allergies or asthma.

Different furnace filters are adept at catching various pollutants. As well as protecting your health, the furnace filter that you use also has a significant impact on the function and maintenance of your HVAC system. As such, choosing the best furnace filters is crucial, but it can be a challenge.

There are many different types available, each with its unique benefits. Many homeowners don’t know where to start, but this article will clear things up for you.

How Does a Furnace Filter Work?

Furnace filters work by catching airborne pollutants as they slip through the air, stopping them from entering your home.

There are many different types of furnace filters, but the basic principle is to catch airborne pollutants entering the HVAC system. Furnace filters trap pollutants from being circulated through your home. A fan draws the indoor air in and forces it through the filter and out of the HVAC system. As the indoor air passes through, other airborne particles like dust or smoke are removed from the airstream. As such, only clean air is introduced into your home.

Most furnace filters are reusable, needing to be cleaned and maintained regularly. However, eventually, your furnace filter will need to be replaced. You can also get disposable replacement filters for your HVAC system.

How Does a Furnace Filter Work?

What is a MERV Rating?

MERV stands for Minimum Efficiency Reporting Value. The MERV scale is a rating system created by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). The rating assigns each furnace filter with an effectiveness score ranging from 1 to 16. These scores are based on how well they remove or capture different airborne contaminants. More specifically, the numbers relate to the size of the airborne particles it can capture, with high MERV ratings meaning that the filter captures smaller airborne particles.

What is a Good MERV Rating?

Higher MERV ratings are better. For residential HVAC systems, you should aim for a high MERV rating of 8-11 or higher.

The maximum MERV rating available is 16, representing an industrial-grade air filter that can trap most particles.

Furnace filters with a rating of 13 or higher are generally used in hospitals and clean rooms because they can trap viruses and other airborne particles.

What is MPR?

MPR stands for Minimum Performance Reporting Value. Another rating system rates furnace filter effectiveness on the same scale as MERV, but instead of using numbers, it uses the letters A, B, C, and D.

A stands for easy to capture particles like larger dust and lint.

B stands for medium-grade particles, such as bacteria and mold spores.

C represents smaller airborne allergens that can be hazardous to your health, such as pet dander and lead. It also includes certain types of smoke and smog.

D represents microscopic particles like viruses and bacteria. Not many furnace filters achieve this rating because it is so high.

What is FPR?

FPR stands for fiberglass performance reporting value. It is a rating system that measures the average number of particles that pass through a furnace filter over time when it is in active use.

What is a MERV Rating?

What Rating Should You Look For?

It can get a little confusing with three different rating systems, and you might wonder which one to look for when choosing a new furnace filter. Other companies will use different ratings, but the majority of furnace filters are put into three main categories:

  • Fair performance
  • Good performance
  • High performance

A fair performance HVAC filter will have a MERV rating of 8. This level of filtration is usually used for air conditioning during the summer months but can be used year-round if you want a basic level of protection.

Good performance furnace filters will have a MERV rating of 11. These are suitable for people who want essential protection from allergens and dust particles.

High-performance furnace filters have a MERV rating of 13 or higher. These are the best you can get for your furnace, as they capture most particles and pollutants.

What Rating Should You Look For?

Different Types of Furnace Filters

Now that you know what the different ratings mean and what you should be looking for, you need to understand the type of filters available to you.

HEPA Filters

HEPA stands for high-efficiency particulate air. HEPA filters are the most effective at removing particles from the airstream, but they are costly and may not be practical for everybody.

These filters use a fine mesh that can trap small particles as small as 0.3 microns in size, around 100 times smaller than the width of a human hair! As such, HEPA filters are considered to be very efficient at removing microscopic particles from your air. They make an excellent choice for allergy sufferers because they reduce pollen and dust.

The MERV rating is as high as 17-20, but they are not suitable for use in your furnace system. In some cases, it could even damage your HVAC, so if you want this level of filtration, consider a separate filter unit with HEPA filters. You should also be aware that pleated filters are almost as efficient.


  • The highest MERV rating of any filter
  • It can even remove viruses from the air


  • Not suitable for most standard residential HVAC units.
HEPA Filters

Carbon Filters

These filters use activated carbon to deodorize your air by trapping harmful gasses like ammonia, formaldehyde, hydrogen sulfide, xylene, and benzene. If you don’t like the idea of breathing in toxic chemicals through your furnace, activated carbon filters are a good choice. The carbon is charged with oxygen, giving it a positive electrical charge, which attracts gasses with a negative charge.

Each carbon molecule is only able to absorb a certain amount of pollutants. Once it is full, it will start releasing these pollutants back into the air through your HVAC system. So, it is crucial to change the filter regularly if you are using carbon filters.

There are non-activated carbon filters available, but these are less effective. The activation process increases the surface area of the carbon molecules, allowing them to capture more pollutants. The thickness of filters varies too, and the thicker ones are more effective as the air spends more time passing through them.

Carbon filters can be very effective, but it is essential to find the right one and make sure that you change it regularly.


  • Removes pollutants that other filters miss, including VOCs (volatile organic compounds)
  • Makes significant improvements to air quality


  • Not as effective at removing small particles like dust and bacteria
  • Must be changed regularly or can release chemicals back into the air.
  • It can be challenging to know when it is time to change them.
Carbon Filters

Electrostatic Filters

Electrostatic filters work by passing a current between metal plates charged with static electricity, which allows them to attract particles. These filters can efficiently capture larger particles like pet hair and pollen, but they struggle with microscopic particles.

Electrostatic filters are available as washable filters or disposable filters. The washable ones are made up of a few layers of plastic (usually polypropylene), which can be taken apart and cleaned regularly. Alternatively, you can get pleated disposable ones made from cotton or polyester.

The advantages of electrostatic filters are disputed. Although they can be effective, they restrict the airflow, putting pressure on your HVAC system. The MERV rating varies, but you can get non-electrostatic filters with equal ratings.


  • It effectively traps dirt in the filter and stops it from being re-released.
  • Available as washable or disposable filters


  • Restricts airflow and can put pressure on your HVAC system
  • More expensive than other types of filter
  • Washable filters can be frustrating to clean
  • Different filters can have equal MERV ratings
Electrostatic Filters

Fiberglass Filters

Fiberglass filters are the cheapest option but not consistently the most effective. Fiberglass filters are made using spun fiberglass to capture larger particles. These filters don’t last as long as the other filters and can reduce airflow but provide adequate protection from particles like pet hair and dust. If the air quality in your home is relatively good anyway, a fiberglass filter may be sufficient, but the MERV rating is usually around 3.


  • Cheapest filters available
  • Easily disposable
  • It does not restrict airflow


  • The lowest MERV rating of any filter
  • Can release pollutants when taking the filter out.
Fiberglass Filters

Pleated Air Filters

Pleated filters are usually made from cotton or polyester and are pleated to increase the surface area of the filter. Pleated filters are very solid and efficient at capturing pollutants and particles. The advantage of this approach is that they don’t need to be replaced as often (depending on the MERV rating) and you get improved airflow. Most will have a MERV rating of 6-12.

Pleated filters are far more efficient than fiberglass ones at catching pollutants, and there are specific types designed for homes with pets. Although they are more expensive than fiberglass ones, they are far better for homes with poor air quality, and they don’t need to be changed as often (roughly every three months).


  • Last a long time before they need changing (3 months)
  • Have a very high MERV rating
  • Easily disposable


  • More expensive than fiberglass filters
  • Restrict airflow can put a strain on HVAC units
Pleated Air Filters

How to Choose the Right Furnace Filter

When choosing a furnace filter, you need to consider your priorities. There is no simple answer to ‘which is best?’ Ultimately, it depends on your home, HVAC unit, budget, and preferences.

The Best Budget Option

Fiberglass filters are the cheapest option available. If you value a low price over everything else, then fiberglass filters might be best for you. Fiberglass filters are so cheap that they’re even a better option than washable ones. Keep in mind that these filters fall in other areas, and if you have poor air quality in the home or allergies, you should consider spending more.

The Best Option for Allergens & Asthma Triggers

Electrostatic filters (washable and disposable) and pleated furnace filters will be able to reduce your exposure to these pollutants/allergens/triggers, and they’re easy to use.

Washable filters require manual cleaning, but pleated filters screw directly onto your HVAC unit, and you can dispose of them when they are full.

If you have allergies, it’s worth spending more to get a pleated furnace filter with a higher MERV rating.

The Best Option for Air Pollution

Carbon filters are the best for air pollution. Carbon filters are most effective at capturing gasses, particularly VOCs, so these filters remove many harmful substances from your home.

Carbon filters are excellent if you are exposed to cigarette smoke or pollutants from nearby roads or factories, for example.

The Best All-Around Option

If you don’t have any specific needs with allergies or air pollution and are just looking for an excellent all-around option, a pleated filter is probably your best bet.

Pleated filters have great MERV ratings (almost as high as a HEPA filter), are relatively affordable, and last a long time. These filters are also one of the best for your air-conditioning unit because they don’t restrict airflow.

How to Choose the Right Furnace Filter

Final Thoughts

Choosing the right filter is very important, but people often make the mistake of only considering the MERV rating and assuming that higher is better, regardless of other factors. But even though it is true that MERV ratings are important, you need to consider other things like the cost, the impact on your HVAC, and the types of pollutants that certain filters can deal with.

Choosing the Right Furnace Filter for Your Home - Final Thoughts