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Microbes, allergens and pollutants plague the air that surrounds us and put us at constant risk of hypersensitive reactions, sickness and respiratory problems. The best air filters trap and neutralize these airborne particles to improve air quality and keep us safe. Air filters also prevent furnace and HVAC (heating, ventilation and air conditioning) systems from malfunctioning due to particles blocking air circulation.

Getting the wrong filter can be both costly and unsafe. To help you get it right, we have created this buying guide to the best furnace and HVAC filters for your needs.  This informative guide defines the key features you should look for when choosing the best air filters and it reviews the different types of filters available.

How to Choose the Right Furnace Filter

It is important to choose the right furnace or HVAC filter, as compromising on the quality can be detrimental to your health. Here are the 3 most essential features that determine the level of protection you can expect, and why they matter when purchasing air filters for your home.

1. MERV Rating

Numbers don’t lie, especially when they come from authorized professional bodies designed to be industry gatekeepers of quality control.

The best way to measure the effectiveness of an air filter at removing harmful airborne particles is by its MERV (Minimum Efficiency Reporting Value) rating, a standard testing system by the American National Standards Institute.

MERV ratings range from 1 to 16, where a higher rating indicates finer filtration and greater effectiveness against airborne particles.

MERV rating of 1 to 4: air filters in this range capture large particles 10 microns or larger. Since 99% of airborne particles are much smaller than this, it makes them unsuitable for improving air quality. Typically you’ll find these in systems that can be clogged by large debris, like window AC units.

MERV rating of 5 to 8: filters in this range are decent at capturing most common particles sized 3–10 microns, such as mold spores, dust mite, and pet dander. (For perspective, the diameter of a human hair is 50 microns.) You’ll find these filters used in many residential homes and commercial buildings.

MERV rating of 9 to 12: these high-performing air filters effectively filter out smoke, dust, pollen, and other 1–3 microns particles. You’ll find air filters in this range in better residential homes and hospital laboratories.

MERV rating of 13 to 16: air filters with the highest MERV ratings offer the ultimate protection from bacteria, the flu virus, and contaminants as tiny as 0.03 - 1 microns in size. You’ll find these used in hospitals and general surgery.

So, is the highest MERV-rated filter the best for your home? Not necessarily.

The highest MERV ratings cause increased air resistance in your furnace or HVAC, overworking your system and decreasing its efficiency. To be on the safe side, choose an air filter with a MERV rating range of 8 to 12 to strike a balance between improving air quality and protecting your HVAC system.

2. MPR Rating

Another key rating is MPR (Microparticle Performance Rating) by 3M, which measures the efficiency and effectiveness of a filter to remove particles that are smaller than 1 micron.

Filters are rated from MPR 300 to MPR 2800. A high value shows superior performance.

Similarly to MERV ratings, too high an MPR will lower the efficiency of your system. Look for MPR 1000 to MPR 1900 for a good balance of effective filtering and HVAC performance.

3. Filter Size

Furnace and HVAC systems are designated to work with filters of specific sizes, with the filter thickness dictating how well the air cleaner will work at preventing accumulation of dust and debris on the heat exchanger. The two common thicknesses are 1 inch and 4 inches.  

If the air filter does not fit snugly, unfiltered air can bypass the filter and pollute your surroundings. Look for labels on your air filter to indicate the size of filter you need. It it’s unmarked, search for the model of your furnace or HVAC, as different models -- even from the same brand -- can require different filter sizes.

Most Common Types of Furnace and HVAC Filters

Furnace and HVAC air filters feature different designs that optimize their effectiveness at removing specific contaminants. The following are the most common:


One of the first steps is deciding whether you want a disposable or reusable air filter. They are an inexpensive option to begin with and usually need changing once a month. Disposable filters can have a MERV up to 16, which means they do a good job at collecting fine particles.


Every air purifier needs to have a pre-filter. A pre-filter captures particles that are bigger than 5 microns, and this means that the main filter can focus on capturing finer particles without clogging.  This increases the lifespan of the main filter.


This is commonly spotted in inexpensive filters with a low MERV rating of 4, or below. They have thin and flat surfaces that are capable of removing 25% of pollutants that are in the 3 to 10 micron range. However, their inefficiency at capturing small particles which form the majority of harmful pollutants makes them unsuitable for air quality improvement.


This design is popular in mid-range models that are made of polyester or cotton. The pleated design provides a large surface for air filtration and entrapment of more airborne particles. Pleated filters are much more efficient than non-pleated filters at capturing respirable particles, according to the EPA (Environmental Protection Agency). However, the increased capacity can cause a quick buildup of debris which necessitates frequent replacement.


This filter is regarded as the gold standard due to its ability to remove small 0.3 micron particles at an accuracy rate of 99.97%. More air cleaners are adopting them due to their efficiency and protection from a wide range of airborne contaminants. They are ideal for people who are prone to allergies.

Activated carbon

Activated carbon filters can be used in conjunction with HEPA filters to trap known allergens and impurities. They are best known for its highly-absorbent properties that eliminate odor, smoke, chemicals, and other gaseous pollutants. Smokers and pet owners will find this filter convenient.

Other Types of Furnace and HVAC Filters


Although germaphobes might wince at the thought of recycling air conditioner filters, these permanent eco-friendly models are convenient and economical. However they can take effort to remove, clean and reinstall. They may also be more expensive at the outset.


Electrostatic filters work with a clever trick of electromagnetism. Like a magnet, they attract floating particles in the air such as dust and bacteria, pulling them to the metal in the air filters. The particles stick to the metal instead of staying in the air. An electrostatic filter should be checked every week to see if it needs to be washed.

UV (Ultraviolet)

This type of filter utilizes ultraviolet light to kill mold in line-of-sight. UV filters are another great option for people with respiratory problems. In fact, studies have shown that UV lights reduce fungal contamination within air-handling units.

Why You Need to Change Your Air Filters Regularly

Replacing your air filter regularly is the cheapest way to save on energy and maintenance costs.

The major cause of malfunctioning HVAC systems is clogging by pollutants. As the trapped particles accumulate and coat the tubes and ducts, air movement is restricted.

The buildup overworks your heating and cooling systems because they have to struggle to push air through the obstacles. This will run up your energy bill.

This can even lead to a complete shutdown of the system, and an expensive visit from the servicing company.

But most importantly, when your filter accumulates airborne impurities you increase your exposure to allergies, sickness and infection. Subscribing to a regular delivery of fresh air filters is an easy and inexpensive way to keep you and all of the residents in your home healthy.

How Often Should You Change Your Air filter?

It is generally advisable to change your filter every other month.

However, the exact frequency of replacement depends on the type of filter, its usage, the number of household residents, and your health status.

Homes with several people and multiple pets will need to change their filters more frequently to handle the dirt and dander that comes with the increased movement in the house.

The same applies if you live in an area with poor air quality, from construction dust, smoke or even heavy pollen.

If you are vulnerable to hypersensitive reactions, or suffer from respiratory issues, you will need to regularly change your filter, as the health impacts can be severe.

Stocking up on new furnace filters and HVAC filters beforehand will keep your air clean and your systems running smoothly. You can also get a better deal when you subscribe to a regular filter delivery.

The Best Furnace And HVAC Filters

Below we have selected some of the best furnace and HVAC filters in store. Each one is chosen to fit a particular lifestyle and need. If you’re still not sure which to choose, let us know and we’ll help you find the perfect air filter.

Best Air Filter for Allergies and Pets

Lennox X6673 20x25x5 Merv-8


These filters are capable of removing pollen, pet dander, dust mites, mold spores, and allergens. A few other features to be aware of:

  • The pleated design increases surface area for maximum capture and entrapment of particles
  • It does not restrict air flow through the furnace or HVAC system because it has a large holding capacity that takes a while to fill up
  • The package comes with two convenient filters
  • A MERV rating of 8 provides adequate air quality improvement without overwhelming the heating and cleaning system
  • This filter is designed to fit Lennox or any other 20x25x5 systems
  • This filter should be replaced every 3-6 months

Best Air Filter for Dust

Trion Air Bear 255649-101

This model has a MERV rating of 8 which captures mold spores and pollen. This rating also provides good airflow in the furnace and HVAC system. Its features include:

  • The pleats and the three-inch thickness provide a large surface area for maximum entrapment of particles. This improves lifespan because the filter’s capacity allows accommodation of a large number of trapped particles
  • This filter is designed to work with Trion Air Bear
  • The package comes in a pack of three filters that ensure you are always protected

Best Air Filter for Optimal Air Flow

Honeywell 20x25x5 SpaceGard FC100A1037

This filter’s MERV-8 rating is a testament of its power to eliminate pollen and mold spores as well as allergens, dust, and lint from the atmosphere. It also:

  • Captures large particles that could coat the furnace and cause obstruction, and subsequently air flow restriction. This makes it one of the best furnace filters
  • This filter fits F100, F200 & SpaceGard 2200 air purifiers
  • Three filters are included in the package

Best Air Filter for Mold Spores, Mildew and Fungi

21x23x1 MERV-11 Air Furnace Filter

  • This model has a high rating of MERV 11 which indicates efficiency at filtration and superior delivery of clean air
  • It eliminates 95% of most contaminants that are 1 micron and larger, with particular effectiveness against mold spores, mildew and fungi
  • It is generic and versatile enough to work with several types of models. This makes it ideal as both a furnace filter and a HVAC filter
  • Designed to fit 21x23x1 furnaces and HVAC systems


As you’ve learned from this buying guide, there are really two choices you need to make when purchasing the best furnace or HVAC filter for your needs: the level of filtration you need, and the size of filter your system accepts.

For most people and most systems, a MERV rating of 8 to 12 should be sufficient. Filter sizes however come in a wide variety, so check the size you need before you go shopping.

Regularly changing your filter is the key to keeping energy and maintenance costs down, and it will help keep you and your family safe from airborne pollutants. So consider buying in bulk to save money, or subscribing to a regular delivery of brand new filters.

We’ve recommended some good choices above for households with pets, or those who suffer from allergies. Whatever your needs, you can always contact us for more recommendations, or browse the full range of HVAC and filters we stock.



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