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Have a Clean Start! A Comprehensive Guide for Air & Furnace Filters

How often you need to change air & furnace filters HVAC

After the sweltering days of summer, the autumn's coolness offers a perfect time to slow down and relax. The AC used to run all day long during hot summer days and can take a break to enjoy the gentle autumn breeze.

The hinges of seasons is a great time to change your HVAC filter. The HVAC filter is like a lung of your property: It filters out pollutants and gems and gives you clean air to breathe in. At rest, an average adult exchanges approximately 6L of air per minute. This equates minimum of 8640L of air per day. If the air is not safe to breathe in, it is the same as swallowing toxins into your system.

HVAC air filters replacement

How Often You Need to Change the Filter

The biggest factor in how often you should change your filter is the type of filter you use. There are two main filter types to choose from: fibreglass air filters and pleated air filters.

Fibreglass air filters are commonly coloured blue. Out of the two, although they are the more affordable option, they are less efficient at capturing airborne dust and particles. They need to be changed every 30 days or less. As the name suggests, These filters are constructed from continuous glass fibres. They operate in a manner similar to pleated filters, with the primary goal of removing unseen harmful particles from the air in your home.

While pleated air filters may come with a higher upfront cost, they offer greater efficiency in trapping particles. Depending on their MERV rating, these filters can successfully filter out pollen, pet dander, and even tiny pathogens as small as 0.3 microns, providing thorough filtration for even the tiniest bacteria. This feature makes pleated air filters the preferred option for those dealing with allergies, asthma, or similar sensitivities. Typically, pleated filters can remain effective for up to 90 days before requiring replacement, depending on factors such as the season and the environment in your home or business.

HVAC filters replacement frequency

The Size of Your Property

The size of your property also plays a crucial role in determining how often you should change your air filter. In larger properties, where the furnace or air conditioner circulates a greater volume of air, the filter tends to accumulate dirt more rapidly. In the same manner, in smaller properties, where the HVAC system moves less air, you may find that air filter replacements are needed less frequently. What is the MERV rating?

On the packages of air filters, you will find a MERV rating of the product. To find the air filter that fits your needs, we highly recommend getting a product with an adequate MERV rating.

MERV means the Minimum Efficiency Reporting Value, measurement system designed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). MERV ratings serve as indicators of an air filter's ability to reduce airborne particles and contaminants. These ratings are determined based on the smallest size of particles the filter can effectively trap, typically measured in microns. As filters enhance their capacity to enhance indoor air quality, their MERV rating ascends, spanning a scale from 1 to 20.

When evaluating an air filter's filtration capacity, we rely on the term "micron" to determine the smallest particle size it can effectively block. Micron sizes span from the microscopic to those visible to the naked eye. Here's a convenient chart to illustrate this range of micron sizes.

Air filters quality filtration system micron chart

Fibreglass air filters have a MERV rating of 2-4. Pleated air filters have a MERV rating of 5+.

Below is a chart designed to assist you in determining the appropriate MERV rating for a range of different applications.

MERV rating contaminants application chart comparison

MPR and FPR: What's the Difference?

Depending on the products you purchase, you might be able to find additional rating readings such as MPR and/or FPR.

The MERV filter rating is the domestic and international industry standard rating system established by the American Society of Heating, Refrigerating, and Air Conditioning Engineers. Conversely, MPR and FPR ratings were created by private companies, 3M and The Home Depot, respectively.

MPR, the acronym for Microparticles Performance Rating, indicates the filter's ability to capture tiny particles between 0.3 and 1 micron in size. Just like the MERV rating, the greater the MPR, the greater the ability of your filter to trap micro-particles like pollen, pet dander, smoke, bacteria, and viruses from the air as it flows through. Here is a quick reference for your quick comparison with MERV.

  • 100-300 filters lint and dust. Filters rated at 300 MPR also remove dust mite debris. This type of filter equates to MERV 1-4 filters.

  • 600 filters mold spores and pollen in addition to lint, dust, and dust mite debris. It equates to MERV 5-8 filters.

  • 1000-1200 filters pet dander, smoke, and smog in addition to the above pollutants. This MPR filter rating equates to MERV 9-12 filters.

  • 1500+ filters bacteria and virus particles in addition to the above pollutants. This type of filter is equivalent to MERV 12+ filters.


FPR stands for Filter Performance Rating. rating the products on a 1 to 12 scale. Just like MERV and MPR, the higher the number, the greater the ability of the filter to trap pollutants.

  • Good (4-5) equates to MERV 5-8 and MPR 600 filter ratings – trapping dust, lint, dust mites, and pet dander.

  • Better (6-7) equates to MERV 9-12 and MPR 1000-1200 filter ratings – screening out bacteria and mold spores in addition to the dust, lint, dust mites, and pet dander.

  • Best (8-9) equates to MERV 12+ and MPR 1500+ filter ratings – trapping smoke, smog, allergens, and some particles and can carry viruses in addition to particles trapped by the better-rated filter.

  • Premium (10) filters screen out everything that the Best filter traps and also help eliminate odour-causing particles.

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