What's the MERV rating of your air filter? Learn when should you replace it

Are you breathing in the freshest air possible? If you haven't checked the quality of your air filter lately, the answer might surprise you. The MERV rating of your air filter determines how effectively it's cleaning the air in your home. Not sure what that means? Don't worry, we've got you covered.

In this article, we'll explain what the MERV rating is and why it's important. We'll also cover how often you should replace your air filter to keep your air clean and healthy. So, let's dive in and learn more about the air filter that's keeping you breathing easy.

If you're concerned about the air quality in your home, or just want to make sure you're doing everything you can to keep your family healthy, this article is a must-read. Don't let your air filter go unnoticed any longer. Learn everything you need to know about MERV ratings, replacement schedules, and more. Your lungs (and your nose!) will thank you.

What is the MERV rating of an air filter?

MERV stands for "Minimum Efficiency Reporting Value" and is a rating system used to measure the effectiveness of air filters. The higher the MERV rating of an air filter, the more efficient it is in capturing smaller airborne particles.

The rating system ranges from 1 to 20, with 1 being the lowest and 20 being the highest. Filters with a higher MERV rating are capable of trapping smaller particles like dust and allergens, while lower-rated filters primarily capture larger particles like lint and pet hair.

A MERV rating of 6 or higher is generally recommended for residential use, as they provide adequate filtration while allowing for proper airflow. However, certain environments like hospitals or industrial settings may require filters with a higher MERV rating to ensure cleaner air.

It's important to note that while a higher MERV rating can improve the air quality in your home, it may also reduce the airflow of your HVAC system if not properly maintained. Therefore, it's crucial to check and replace your air filter regularly to maintain proper ventilation and prevent potential damage to your system.

How to choose the right MERV rating for your home and HVAC system

Now that you know what a MERV rating is and when to replace your air filter, it's time to choose the right MERV rating for your home and HVAC system.

The MERV rating you choose will depend on several factors such as the size of your home, air quality concerns, and the type of HVAC system you have.

If you have a smaller home or do not have any significant air quality concerns, a MERV rating of 6-8 is typically sufficient. However, if you have allergies or respiratory issues or live in a large household with pets, a higher rating of 9-12 would be ideal.

It's important to note that choosing a higher MERV rating may result in decreased airflow, which can strain your HVAC system. So, it's essential to consult with an HVAC professional to ensure you choose the right MERV rating for your system.

In summary, choosing the right MERV rating for your home and HVAC system is essential in ensuring your indoor air quality remains healthy and ideal for everyone's well-being. Aiming for a higher rating may work for some, but it's equally important to ensure your HVAC system can accommodate the chosen rating without straining or causing damage.

How often should you change your air filter based on MERV rating and usage?

The frequency of air filter replacement depends on the MERV rating and usage of the filter. Generally, it is recommended to replace a filter every 30-90 days, depending on these factors.

If you have a low MERV rating filter (1-4), it will need to be replaced more often due to its lower filtration capability. A filter with a MERV rating of 5-8 may need to be changed every 30-60 days, while a filter with a MERV rating of 9-12 should be replaced every 60-90 days.

Those who live in areas with high levels of air pollution, pet dander, or allergies may need to replace their air filter more frequently to provide optimal filtration. Individuals with respiratory illnesses or compromised immune systems may also need to change their air filter more often to maintain good indoor air quality.

In addition to the MERV rating, the usage of the filter also plays a role in determining how often it should be replaced. A filter in a home with a smoker, for example, will need to be changed more frequently than a filter in a home with only one occupant and no smokers.

Lastly, it is important to follow the manufacturer's recommendations for your specific filter. The packaging or documentation that comes with the filter will provide guidelines on how often it should be replaced to ensure optimal performance.

Regularly changing your air filter is crucial for maintaining good indoor air quality and the longevity of your HVAC system. By understanding your filter's MERV rating and usage, you'll be able to determine how often it should be replaced to keep your home's air fresh and healthy.

4 Red Flags That Signal It's Time to Change Your Air Filter

1. Reduced Airflow: The first red flag to watch out for is reduced airflow from your HVAC system. If you notice that your rooms aren't getting as much air as before, it's highly likely that your filter is dirty and needs replacing. This can also lead to your air conditioner or furnace working harder, increasing your energy bills.

2. Strange Odors: Unpleasant odors can indicate that it's time to change your air filter. If you notice a musty or moldy smell, your filter could be trapping moisture and causing mold growth. Similarly, if you smell something burning or an electrical odor, it may indicate a clogged filter, which can make your system overheat.

3. Dust Buildup: Another sign that your filter needs replacing is excessive dust buildup on surfaces or objects inside your home. If you notice dust accumulating quickly and more than usual, it's a clear sign that your filter is not fully functioning as it should be.

4. Allergy or Respiratory Symptoms: Finally, if you or your family members are experiencing allergy or respiratory symptoms, it may be due to a dirty air filter. A clogged filter can't trap allergens and pollutants effectively, increasing the risk of allergies, asthma, and other respiratory issues.

Keep an eye out for these red flags to avoid any major issues with your HVAC system, improve air quality, and save money on energy bills by changing your air filter on time.

5 Tips for Maintaining Air Quality Beyond Your Air Filter

While replacing your air filter regularly is important for maintaining good indoor air quality, there are other steps you can take to further improve the air in your home or office. Here are five tips for maintaining air quality beyond your air filter:

1. Schedule regular HVAC maintenance: Your heating, ventilation, and air conditioning (HVAC) system plays a big role in your indoor air quality. It's important to have your HVAC system inspected and serviced regularly to ensure that it's functioning properly and not circulating pollutants throughout your home or office.

2. Use an air purifier: An air purifier can be a great way to further clean the air in your home or office. Look for an air purifier with a HEPA filter, as these filters are designed to capture particles as small as 0.3 microns.

3. Keep your floors clean: Dust, pet dander, and other pollutants can accumulate on your floors, especially if you have carpet. Regularly vacuuming and mopping can help keep these pollutants from becoming airborne.

4. Control humidity levels: High humidity can lead to mold growth and worsen respiratory problems. Consider using a dehumidifier to keep humidity levels in check.

5. Avoid smoking indoors: Smoking indoors can release a variety of harmful chemicals and pollutants into the air. If you or someone in your household smokes, consider doing so outdoors or quitting altogether.

By following these tips, you can help ensure that the air you breathe is as clean and healthy as possible. Of course, always remember to regularly replace your air filter as well!


Now that you know about MERV ratings and the importance of replacing air filters, you can take control of the air quality in your home. Create a schedule for checking and changing your air filters, and remember to choose filters with a MERV rating that best suits your needs. A clean air filter will not only improve the air quality in your home, but it can also increase the efficiency of your HVAC system, ultimately saving you money on energy bills. Don't neglect your air filter – your health and your wallet will thank you!

Frequently Asked Question

MERV stands for Minimum Efficiency Reporting Value - a scale created by ASHRAE to measure the effectiveness of filters in removing different sized particles. For example, a MERV-13 filter is designed to catch 90% of particles 3-10 µm in size, 85% of particles 1-3 µm in size (PM2.5), and 50% of particles 0.3-1 µm in size. Generally, filters with higher MERV ratings are better at catching higher percentages of particles, including the smaller ones.

When you install a filter in the airstream, it will create resistance. The amount of resistance depends on the type of filter material and the amount of area it covers. Standard fiberglass filters don’t generate much resistance, though it increases as the filter gets dirtier. To remove more pollutants from the air, you can use a filter with a different material such as a high MERV filter. These filters have smaller pores, which allow them to catch more pollutants, but also create higher resistance.

The problem with this is that the blower and furnace are only designed to handle a certain amount of pressure drop. Too much resistance means the air flow is low, making the heat exchanger get hotter and potentially crack. On the plus side, low air flow can result in better dehumidification in humid climates, as long as the air flow isn’t so low that it turns the condensate to ice.

So, the answer to the question is: yes, higher MERV filters are better, but you need to find the right balance between air flow, resistance, and effectiveness.

Air filters are designed to capture airborne particles, which can be anything from dust and pollen to mold spores and bacteria. The filter works by drawing air through itself and trapping the particles in the web of fibers that make up the filter.

What are the types of air filters

There are many different types of air filters available on the market. The type of filter you need will depend on the specific needs of your facility. Some common types of air filters include MERV, HEPA, activated carbon, and ultraviolet (UV) germicidal irradiation.

MERV: MERV stands for Minimum Efficiency Reporting Value. MERV ratings range from MERV-0 to MERV-16. The higher the MERV rating, the more efficient the filter is at capturing particles.

HEPA: HEPA filters are a type of air filter that is designed to capture very small particles. A true HEPA filter has a MERV rating of 17-20.

Activated carbon: Activated carbon filters are designed to remove gases and odors from the air.

UV germicidal irradiation: UV germicidal irradiation is a type of light that is used to kill bacteria and viruses.

There are pleated filters and panel filters. MERV 13 filters are pleated, while MERV 16 filters can be either pleated or panel. Pleated filters have more surface area because they are made up of multiple layers of filter media. The pleats create more space for the air to flow through, and the more layers of filter media there are, the more particles can be captured.

HEPA filters are usually pleated, but they can also be panel.

What are the differences between MERV 13 vs HEPA filters

While MERV 13 and HEPA filters both remove particles from the air, they work in different ways.

MERV 13 filters are designed to remove particles that are larger than 0.30 microns, while HEPA filters are designed to remove particles that are smaller than 0.30 microns. MERV 13 filters are often used in commercial and industrial settings, while HEPA filters are often used in hospitals and other medical settings.

MERV 13 filters are more efficient at removing large particles from the air, while HEPA filters are more efficient at removing small particles from the air. MERV 13 filters can remove up to 99.97% of particles from the air, while HEPA filters can remove up to 99.99% of particles from the air.

MERV 13 filters are less expensive than HEPA filters, and they can be used in a wider variety of settings. However, HEPA filters are more effective at removing small particles from the air, and they can be used in settings where MERV 13 filters cannot.

MERV and HEPA filters both work to capture airborne particles, but they do so in different ways. MERV 13 filters are designed to capture particles larger than 0.30 microns, while HEPA filters are designed to capture particles smaller than 0.30 microns. MERV 13 filters are more efficient at removing large particles from the air, while HEPA filters are better at capturing small particles. 

MERV 13 filters are less expensive and can be used in a wider variety of settings, but they can only remove up to 99.97% of particles from the air. On the other hand, HEPA filters are more expensive but can remove up to 99.99% of particles, making them ideal for medical settings. In short, MERV 13 filters are great for everyday use, while HEPA filters are better for specialized environments.

Your HVAC system includes a furnace, air conditioner, or heat pump. It's essential to keep these systems clean and efficient by regularly replacing the air filters. To do this, you'll need to know about MERV ratings.

The air filter in your HVAC system serves two key functions: it protects your system from dust, and it helps clean the air in your home. When the filter is clogged, dust can build up in the system, and the equipment may overheat and fail.

How often the air filter needs to be changed depends on your home's size, where you live, and if you have pets. Inspect it every month, and replace it when you can't see the filter material through the dust.

When choosing an air filter, refer to the specifications of your HVAC system to determine the size. The MERV scale is used to measure the filter's ability to remove particles from the air, and ratings range from 1 to 20, with lower ratings meaning lower-quality filters.

Remember to balance air cleaning with air flow when upgrading your filter to a higher MERV rating. Too dense of a filter can cause air flow restriction and harm your system. Ask your HVAC technician for advice when in doubt.

Replacing the air filter is easy. Open the blower compartment located between the air return and the furnace or air handler. Put the used filter in a plastic bag, then insert the new filter with the arrows pointing in the direction of the airflow.

MERV 11 filters used to be thought of as air flow restrictors, but this is no longer necessarily the case. Home Energy's 2009 experimental test concluded that the pressure drop of high-MERV filters isn't as severe as it used to be. If you're renting and don't have any special needs, then a standard, cheap fiberglass filter with a cardboard frame is fine to use every three months. But if you own your home, then it's worth investing in a more durable filter.

Pleated filters with more pleats per foot are the better option and should be more effective at improving indoor air quality. However, the price can be an issue. A standard 16x25x1 11 MERV filter will cost around $5, but you can save a bit if you buy them in packs of 12. Filtrete, Purolator, and Nordic Pure are all trusted brands.

If you plan to buy washable filters, be aware that cheaper models may have loose filter media after washing and won't perform as well. Disposable filters are also more hygienic since they remove all the dirt from the air. Keep in mind that the more pleats per foot, the better the filter will be.

So, when it comes to MERV 11, the issue of air flow restriction isn't as big as it used to be. With the right filter, you can improve your indoor air quality without having to worry about a pressure drop. Make sure to replace your filter every three months for the best performance.

MERV ratings are used to compare filters to determine which is most effective for eliminating pollutants in a home or office. The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) developed the Minimum Efficiency Reporting Value (MERV) system to measure how well an air filter captures common airborne particles. There are 16 MERV values, ranging from 1 to 16, and the efficiency increases with the MERV number.

Filters are tested against 12 size ranges of particles, with the smallest being around 0.3 microns and the largest around 10 microns. To give a sense of the size, a micron is one millionth of a meter and a strand of human hair is approximately 75 to 100 microns.

The MERV rating is determined by measuring the particle count upstream and downstream of the filter being tested over six intervals, beginning with a clean filter. Afterward, a special ASHRAE test dust is added for five additional measurement cycles. The filter’s performance is determined by calculating the particle density before and after passing through the filter, and then assigning a MERV rating.

The MERV 8 filter is the most common filter in the U.S. Understanding how MERV ratings work can help you understand why it's so popular and how to choose the most beneficial filter for your needs.